A vapor barrier under laminate floor, required for most laminate flooring installed over concrete. This vapor barrier which is actually a vapor retarder helps to keep moisture vapor from entering into the laminate floor. Concrete substrate must be tested in accordance with the flooring manufacturers instructions. Excessive moisture can be found in a concrete slab of any age. Not all manufacturers require the same tests and not all floors are the same. All-in-one laminate underlayment cushions with a vapor retarder attached are available.
A Vapor Barrier Under Laminate Floor Reduces Damage
Interior Vapor Retarder Over Concrete Subfloor
When a laminate floor is installed over a concrete subfloor a moisture barrier must be used. Most every laminate manufacturer will require a vapor barrier under laminate flooring. Not sure, check the manufacturers installation guide for the flooring that you are installing.
Failure to install a proper vapor retarder over concrete will likely result in a floor expanding. This will cause laminate floor problems such as cupping and gaps.
Always check a manufacturers installation instructions prior to installation to assure that proper procedures are followed and proper materials are used.
Do Not Use a Vapor Barrier “Retarder” on Wood Sub Floors
It is important to note that you DO NOT install a vapor barrier under laminate floor that is installed over a wood subfloor. Over wood a vapor barrier will trap moisture and cause damage. Some laminate underlayments are a combination of vapor barrier and foam so take care in selection.
While most manufacturers, NALFA and NWFA flooring associations do not recommend the use of a vapor barrier (moisture retarder) over wood subfloors their are laminate manufacturers such as Harmonics that do. If the manufacturer of your laminate products requires you use their moisture barrier over wood, use it, but ONLY the moisture barrier they say to use. Be sure to follow their installation directions carefully. Harmonics for example states, “For wooden subfloors, cut the moisture barrier 1 inch from the wall.” The reason for this is to give any trapped moisture trapped below to have an opportunity to gas off at the side of the wall. This is unlike the requirement to run the moisture barrier up the wall when the laminate floor is being installed over concrete.
A foam or other type underlayment approved by the laminate manufacturer needs to be used for installation over wood subfloor.
I have been surfing the internet to answer some questions, and so far this website has been the only one that comes close to giving me some answers.And just for that, I thank you.
We have pergo select laminate flooring . Unfortunately, we recently had a slab leak under these floors– warm spots on the floor and actual water coming out of the concrete slab in the garage which is adjacent to the pergo flooring and the supposed pipe leak.We have stopped the leak and so far we have not seen any buckling or cupping on our floors (yet?). The water restoration technicians came the same day that we found out about the leak, and using a hand-held device that he put on the floor to detect moisture, concluded that there is no moisture detected(the thing did not beep) on the pergo floors or the adjacent walls. When the pergo was installed, I remember that the pergo-authorized installer put on some “moisture block” underlayment on the concrete slab under the laminate. He also glued the edgesof the pergo instead of just clicking them on together.
My questions are:
How accurate are these Moisture detecting devices when used on Pergo?
If the moisture block underlayment did it’s job, will it still need to be checked for molds underneath and replaced?
What simple measures can I take now to prevent molds/fungus from growing under the pergo?
Will I see some buckling/cupping or any obvious damage when everything dries up and/or in the future?
Should I still have the pergo replaced even without the cupping or buckling? I’m really concerned about mold/fungus growing underneath the floors.
Also, they did find some water damage in the bathroom and the adjacent laundry room walls so they set up containment there and are presently doing “dry-up” procedures–blower fans and a dehumidifier. since they did not detect any moisture on the floors in the hallway, only part but not all of the affected pergo floor is being dehumidified.
I apologize about the extensive post but I hope I made myself understandable. I also hope you could give me some answers….soon.
Thanks a bunch.
Moisture meters are very good as showing if there is moisture under the laminate. If there is not moisture you should not experience in moisture swelling of buckling. It is possible that you could still get expansion of the planks if the relative humidity is not controlled but it sounds as if they have that under control. As far a mold under the planks mold develops where there is warmth and moisture and if the area did not get wet you should be fine there.
After two months, the laminate installed over a hardwood tile floor, has bubbles, what is it?
Luis, Without seeing a picture of the bubbles I can only tell you that the most common cause of bubbles that appear after installation is moisture. If the bubbles cross between the joined edges of the planks moisture is the most likely cause. Email a picture if you can and we will take a look at it.
Terry
Andy, with a floating floor you will often feel a bit of give with a lot of this depending on factors such as the type of underlayment used and the subfloor the laminate is installed over. If the floor has developed peaks and valleys since installation it sounds like an expansion concern. If inadequate expansion space was left around walls and other fixed objects or the laminate has expanded from a moisture gain it may now be locked in by walls or other fixed objects and with expansion it was unable to move any way but up. To visually check for expansion you would need to remove the baseboards. You can also do a random check by placing an offset feeler gauge under the baseboards to see if there is a gap between the edge of the planks and the walls and other fixed objects. Even a small amount of lock in such as along a sliding door, fireplace and nails through transition can cause the types of problems you are mentioning. There are other causes besides lock in and to know for sure what is going on and what you need to do to correct the situation you might want to contact a good flooring contractor or inspector in your area to check it out.
Terry
Do I need to put vapor barrier down before putting the pergo flooring down? The subfloor is wood and it will go over a crawl space that is not insulated under the floor and no vapor barrier is on the ground.
Keith, that is an excellent question that confuses a lot of people. On a wood subfloor you will not need a vapor barrier. You will need to use a cushion foam or other type underlayment under the laminate if one is not already attached. If you are using Pergo make sure it is one approved by Pergo. If another manufacturers laminate make sure it is approve by them.
Make sure the vapor barrier over the earth in the crawl space is in good condition and that all of the ground is properly covered.
Regardless of the product used be sure to read and follow the manufacturers installation instructions and if you hire a contractor read them to make sure they do the job correctly.
Terry
I installed a foam backed laminate floor over concrete without a moisture barrier. 11 months later I now have mold/mildew growing betwwen the planks. The concrete was dry(meter checked) at time of installation. I was told a moisture barrier was not needed. Who is a fault and what happened?
Sandy
When installing a laminate floor over concrete a vapor barrier is required. A concrete floor may be years old and appear perfectly dry at time of installation and then suddenly become too wet. I do not know of any laminate manufacturer that does not require a vapor barrier when installed over a concrete slab. If you have a way of proving that the dealer or flooring contractor told you a vapor barrier was not required you may have an action against them. If the manufacturers installation instructions do not state that a moisture barrier is required and the floor fails for that reason you may have an action against the manufacturer.
Terry
Hello, You have some great advice on here and I thank you for it. I installed Dupont Real Touch Classic in my den (converted garage) about 1 year ago. I also installed it in the hall and living room at the same time.I installed moisture barrier and cushioning as stated. I noticed that in the den it has moisture under it and is ruining the flooring. I pulled a couple of pieces up and found water under it. The house was built around 1973. I am going to do the 2 foot plastic with duct tape today, but I was wondering one thing: the spot that is the wettest is the spot that goes into the laundry room. The laundry room has stick on tile and no a/c. Could the temperature difference from the laundry room to the den have some bearing on this? I have a threshold down, but the laminate and barrier ends under the threshold with no sealant. Could the humidity difference in both rooms have caused this? Thank you in advance for your time.
Michael
You state that you installed the moisture barrier yet later in your comment you say that your are “going to do the 2 foot plastic with duct tape today.” The DuPont installation instructions state, ” you must first lay down a 6-mil plastic sheet vapor barrier. Sheeting should overlap at least 7-8 inches and run wall-to-wall. Secure seams with masking tape.” If the sheeting was not installed from the beginning the moisture may be coming from the concrete though that does not sound like the cause as you state, “the wettest is the spot that goes into the laundry room.”
As far as humidity being the culprit that sounds doubtful as you are finding localized water and if the humidity was that great even to leave water under the laminate (and it would have to be continuously extremely high) the stick on tile should be releasing in the laundry room.
Based on your description the most likely cause of the water under the laminate is a slow plumbing leak, drip, or spill that occurred after the installation of the laminate. Check your faucets and washer for a slow leak or drip. Unless you can actually see where the water is coming from testing at the jobsite by a plumber or other person equipped to do leak detection will be required to pinpoint the cause.
Terry
Terry,
The 2 foot thing with duct tape is the moisture test where I pulled up the couple of pieces yesterday that are bad. I am a master plumber (30 years) and we have no pipes under the slab in this area and the closest place is the laundry room which is close to where I pulled up the couple of bad pieces of laminate. i am seeing no water coming from there. my wife ran the washing machine yesterday after I pulled it up and we can find no trace of water. I did lay down the 6 mil first as instructions stated. This is a real puzzle. I will keep looking for the cause. Thanks and let me know if you have any other thoughts on this.
Michael
It sounds like you have attempted to eliminate plumbing as an issue. It further sounds like you are describing a mat test to test for moisture. For those of you not familiar with a mat test this is a test to check concrete for moisture. What you do is take a piece of plastic sheeting such as Visqueen that is about 36″ x 36″ in size, place it on the concrete and tape it around the perimeter using duct tape. Leave the material adhered to the concrete for a minimum of 72 hours. Remove the plastic and you have a moisture concern if you see water, the concrete is damp or has the appearance of being wet. If the concrete appears to show moisture and you want to get a truer picture of how much moisture is there you need to have the slab tested using either a Calcium Chloride tests or in-Situ Relative Humidity test where the relative humidity within the slab is measured. Even on an concrete slab that has been there for years moisture concerns can develop. I would suggest that you contact a professional flooring inspector and have an on site inspection and testing performed.
Terry
My house is on piers. My husband and I installed laminate flooring and used the foam type plastic barrier over a second subfloor and we’ve discovered we have mold between the plastic and the second subfloor….none between the plastic and laminate flooring. I say second subfloor because there is the original wood slat flooring, then a plywood flooring and then the laminate flooring. About a year ago we had to take up the laminate flooring and fix a section in the plywood flooring that had bubbled up. We don’t think my brother who installed it put enough screws so we assume moisture caused it to bubble up. At that time there was no mold or mildew. We replaced the whole piece of plywood that was affected. Since then we’ve had other areas bubble up so we removed the laminate flooring this past weekend and discovered the mold and it is through out the whole house between the plastic and plywood subfloor. I’m confused…..you say not to apply a moisture vapor barrier when installing laminate flooring on a wood subfloor but then you say “A foam or other type underlayment approved by the laminate manufacturer (which we used the manufacturers requirement) needs to be used for installation over wood subfloor. So if you can understand what all I’ve said do I use the plasic foam underlayment or not???? And should we paint the plywood subfloor with a mold/mildew resistant paint before we reapply the laminate flooring. We washed the subfloors with pure vinegar. Any help would be very much appreciated.
Mary
When we talk of vapor barriers this can sometimes become confusing and easily misunderstood. For laminate floors you have a number of foam and other types of cushions that will retard moisture along with vapor barriers which are sometimes called vapor retarder. The cushions designed to be used over a wood subfloor do not have a plastic vapor barrier attached. The cushions used under laminate also provide benefits such as reducing noise and eliminate wood-on-wood contact.
Vapor barriers can be a membrane, vapor resistant material, or covering with a vapor resistance rating at or above .7 perms, or at or below 50 perms. The primary purpose of a vapor barrier is to reduce problems of damage to the laminate from ground moisture and condensation.
With a wood subfloor, an impermeable vapor barrier with a rating of .7 or less shouldn’t be used as these can trap moisture in or on the wood subfloor. When moisture is trapped many types of problems can occur.
Terry
I have pergo installed in a kitchen and recently was notified by my tenants there are small bubbles of water coming up between pergo planks. The property is located in Tucson, AZ. This is a very dry climate, except in the summer during Monsoon season, which even then the humidity might hit 60% on a very rainy day.
The localized area is right in front of the sink cabinet. The pergo planks are now starting to slightly buckle. I contacted my home owners insurance company and they sent out an Adjustor. He was unable to determine where the water was coming from. He then contacted a water leak detection contractor. The water detection contractor found the swamp cooler on the roof could be the cause of water slowing accumulating under the pergo. He stated the overflow valve for the unit needed to be adjusted and the timed overflow spilling of water that drains thru pvc pipe was entering thru the roof near the sewer vent pipe. Upon inspection of roof vent pipe, this roof area is sealed and no water damage to this area of roof. I am far from convinced he pinpointed the source of water leakage. All plumbing was checked, ie dishwasher, ice maker, faucet etc. Approximately 5 months ago the kitchen had a defective faucet and some water leakage. No obvious damage. Now 5 months later the damage to pergo is apparent. Could this be residual from a minor faucet leak , and a contributing factor of the increase in humidity? We installed the pergo with the recommended vapor barrier, we didnot test the concrete slab, as we are in Arizona where it is dry as a bone!!!
The house was built in 1959. The pergo looks absolutely stunning in the kitchen, and I did have my reservations prior to installing the pergo in case of a water leak, but chose to install the pergo. The entire localized area of floor is approx. 4 x 4.
My insurance company recommended water clean up company. This company came out and stated they would set up 2 small dehumidifiers for 3-5 days at the cost of $1500 to $2000 depending on how long the dehumidifiers would be needed. I have a $1000.00 deductible. This was not an acceptable amount for the small area. I could pull up all the pergo and install tile for less than that, but it would not be an exact match for the existing hallway and bathroom tile, as the porcelain tile I used has been discontinued and so has the pergo I used. Luckily i still have several boxes of pergo left over and have enought to cover the area.
I think if I pull up or use a small saw to cut through the middle of one of pergo to allow this trapped moisture/water to be released, continue using fans and allow several days for this area to dry, I could then replace the pergo planks.
I apologize for this extensive message but thought I should share as much info with you as possible! We are do-it-yourself people and feel that contractors relish in the fact this is an easy rip off as this is a claim with the home insurance company. Please provide your recommendations. The tenants have a large fan on the floor and are using the swamp cooler as little as possible. Thank you for your consideration regarding my request.
Audrey
Audrey
The damage to the Pergo that is near the sink could indeed be from a several month old water leakage. Since you have several boxes of the plank your thought of removing the damage planks and replacing that area makes a lot of since and that is exactly what I would do if the floor was in my own home. You should only need to remove the area where the planks are damaged, dry the area thoroughly, test for moisture and if it shows dry go ahead with the installation. You have a $1,000 deductible and the repair should be less than that so it does not make sense to have a claim that might result in a premium increase. Even though you like to do it yourself you may want to use a flooring contractor that has a lot of experience with partial laminate replacement and the proper meter to test for moisture.
Terry
Help!!!!
Our home had a deck that was covered by our roof (sort of like a car port). We have enclosed most of the deck to make it into a room. Underneath the deck is essentially a crawl space except that is not sealed off as much a crawl space would be. The part that has been enclosed has had a subflooring placed on top of the deck boards. There are vertical pieces of deck boards that form one wall of the crawl space (but gaps between the boards as you would typically see). So…..it is quite likely that the underneath of the crawl space will be subject to summer highs, winter lows and moisture in the air. Currently there is no vapor barrier on the ground in the new crawl space, but not sure it would do a lot of good since one side of the crawl space could almost be considered to be open via the vertical deck boards. What would be our best options (type of flooring) to use in our new room?
thanks
John
John
I would play it safe and select a floor covering that is approved for outdoor installation such as interlocking rubber tile. While I don’t like to recommend particular products at this site you can find lots of outdoor floor covering products by performing a Google search.
Terry
Hi Terry,
I have read alot about installing a vapor barrier over a concrete subfloor. The one aspect that I can not seem to find an answer on is what to do where the poly moisture barrier meets the walls. Do you leave the poly only flat on the floor at the edges without sealing it? Or do you go a few inches up the wall with the poly and tape it to the walls?
Thanks,
Mike
Mike
That is an excellent question and I am glad you asked it. A vapor barrier should be turned where the floor meets the wall and ran up the wall a couple of inches. A properly selected and installed baseboard will cover the vapor barrier.
Terry
Hello,
Some great info here. You have sort of answered this question throught this feed but I am looking for some specific reassurance. I am installing laminate on a basement floor as part of an insurance claim due to a sewage leak. I want to purchase the foam backed laminate from costco and put 6mm vapor barrier under it. The contractor in charge of the job said that they would not put the poly barrier down becuase it would cause mold issues underneath. I am not convinced that eliminating the barrier is a good idea. Further, how would it be any different than a glued linoleum? Any incite would be appreciated.
Adam
Since this is a basement you most certainly have a concrete slab. If the contractor is concerned with a potential mold issue developing with the use of the poly barrier which raises a red flag and I would be concerned with the condition of the slab. Mold develops in areas where you have moisture and warmth.
Laminate floors will not hold up against moisture. I would insist that the concrete be tested for moisture content using a test method such as calcium chloride or in slab humidity testing but first make sure it is approved by the manufacturer of the flooring and what standards the slab will need to meet. Costco should be able to obtain for you printed or on-line installation requirements and/or the contact information for the manufacturers technical department.
If the manufacturer requires a particular type of test and a particular vapor barrier and you fail to use it then you have no warranty. As far as a glued linoleum you also must go by their testing and installation requirements if you want a warranty. Again the very mention of mold with the use of a vapor barrier raises a red flag.
Terry
I’m installing laminate over a concrete floor. I’ve installed a plastic vapor barrier and now notice with about 8sq ft completed that when I walk on the floor I can hear the crumbling of the vapor barrier. Will this dissipate over time or should I stop now and make sure the vapor barrier is tight to the floor.
Thanks
Eric
If you are noticing the problem now it needs to be addressed now as it is highly unlikely that the noise will dissipate later. Make sure you are using an approved brand of underlayment and vapor barrier for the product you are installing. Let your dealer know what is going on before you get to far along for they may suggest that you use a different vapor barrier.
Terry
Hi there. I am very confused right now. I am located in the northeast and am in the process of installing a new subfloor in my basement. In this particular room there is a perimeter drain that always has water flowing through it (no cover over the drain). I plan on installing pressure treated 2×4’s over the concrete with advantech plywood on top of that then a finshed floor (probably vinyl). Should I or should I not place a vapor barrier between the concrete and the pressure treated 2×4 sleepers? I hesitate to install the vapor barrier because I am worried about the potenial mold growth between the concrete and the 6mil plastic.
Thoughts or recommendations would be greatly appriciated.
thanks
Jeff, you must be especially careful to follow the instructions for the flooring product that you choose to use. If they require a vapor barrier it MUST be used or the warranty will not be any good.
Terry
Hi. I have Presto Pergo installed throughout most of my house. The kitchen, family room and entry way were installed in 2003, and have had no problems with it. In 2010, I had Pergo installed in my living room and hallway to replace carpeting. The hallway is holding up fine, but the living room has had to be replaced once already due to moisture on the slab. The contractor that laid the floor used a 3-in 1 underlayment, which turned out to not be sufficient for the concrete slab. He replaced the flooring on his dime and used the 6 mil polyethylene sheeting and the silent step foam underneath. Its been about 6 months, and the floor is starting to warp and buckle on four consecutive boards. It sounds like there is water underneath. I don’t understand why there is only a problem in this room with moisture, yet most of my house has Pergo flooring and have had no problems. I had carpet in this room for 8 years and never had a problem with moisture. Any insight you can give me, would be helpful. I don’t know whether to call a plumber, or just put carpet back in that room.
Thanks
I live in a split level house, where front of house is 4 feet below grade back of house is maybe 1 foot below , i want to instal laminate in a downstairs bedroom and dining room over existing tile (house was built in 70s pretty sure glue holding tiles has asbestos) so install would be slab – current tile- new laminate floor. do i need a moisture barrier between tile and laminate?
Gina
You question if you should call a plumber or replace your Pergo laminate with carpet. The only way you are going to know is to determine where the moisture is coming from. You describe the problem as being in a small area of the living room. Has a moisture test been performed to see just how extensive the problem is below? If a topical moisture test shows it confined to an area of just a few square feet the problem is probably topical moisture from an incident like a spill that you did not know about. If the topical moisture test shows it over a very large area it could be the concrete, a plumbing problem or again a potential topical or maintenance problem. You really need to get a person in there such as a flooring contractor with testing experience or certified flooring inspector that has the knowledge to make the proper test. You can use a company like the Weinheimer Group or find an inspector for your area at http://nicfi.org/
Terry
Terry
Ronnie
Since you are talking about a below grade installation laminate is not going to be a good choice and would have an excellent chance of failing. You may want to consider an engineered wood product and yes you will need to use a moisture barrier unless the manufacturer of the flooring product states in their installation manual that one is not needed. Before purchasing any flooring product obtain the literature of the manufacturer that shows the product is approved for a below grade installation. (Can usually be found on the internet.) Be aware that the flooring manufacturer either laminate or engineered wood will almost certainly require a vapor barrier so read their instructions carefully even if you hire a flooring installer to make the installation.
Terry
I have a converted garage into a play room in south Florida. I installed carpet tiles about 2 years ago. I now have mold. I am going to remove the tiles and mold. Then I’m considering my flooring options. If I install a vapor barrier then laminate flooring what stops mold growth between the barrier and the concrete floor? If nothing, does the barrier “trap” the mold thus poses nothing to be concerned about.
Tommy
You pose an excellent question. If you have a mold problem you will need to correct it before you install a new floor. If you just try to cover it up with a vapor barrier your floor may still fail and worst of all you are dealing with possible health issues. My suggestion is to find the cause of the mold and correct it. After correction make sure that it not only appears corrected but test also show it corrected. Also make sure the concrete moisture level is with in acceptable limits for the floor that you choose to install.
Good luck, Terry
The source of the mold is from moisture coming up through the concrete slab. There was no vapor barrier installed when the house was build because it was never intended to be an air conditioned space. So I ask what are my options?
Tommy
If moisture is coming up through the concrete slab resulting in mold, your best option is to find the cause of the problem and correct it before installing a new flooring product – especially laminate or wood. Sorry to be the bearer of bad news but any option other than proper correction is just setting yourself up for failure.
Terry
I hope my question is simple, we had a minor flood in our kitchen about a month ago and the water soaked through the floors into the basement (semi finished and not a crawlspace, its our laundry room) and we did the cleanup and dried it out very well (so i thought). so, we had to rip out the flooring yesterday because it was warped so badly, also the particle board layer (used on top of the Plywood subfloor). i am going to replace the particleboard that was ruined and am planning on putting Pergo in as a replacement for the ruined laminate.
So,here is my setup.
laundry room in basement (no finished ceiling)
above laundry room is the kitchen, plywood subfloor with a layer of particle board on top of the plywood subfloor.
Here is my question, do i need to install a moisture barrier, in addition to the underlayment and the new flooring? i am worried the moisture barrier will trap the moisture (like it did recently) between the 2 wood layers.
please let me know your thoughts on this as i am getting mixed opinions on this. BTW, i live in Colorado and we get all 4 seasons here but generally it is pretty dry here (not much moisture in the air)
Ryan
Since you are installing the flooring upstairs in the kitchen over a plywood and particleboard subfloor you will not use a vapor barrier. What you will use is a foam cushion or other underlayment cushion that is approved by Pergo if that is what you install. Remember that all laminate floors are not the same and the required cushion underlayment is not the same for all floors. When selecting the laminate you want to use be sure to read the installation instructions for that particular product and purchase a foam or other cushion underlayment that is approved for that floor.
Terry
I am installing a Swift Lock Laminate Floor on concrete. The pad I bought has a plastic backing by Precision Components. It doesn’t say mil thickness. Can I install a 6 mil poly on the concrete then install the pad I bought with the plastic backing? The pad says it is a Vapor Barrier but it doesn’t appear to be 6 mil. Can two Vapor Barrier be put down? Would you recommend two plastic barriers? My concern is the pad with the plastic backing be sufficient?
Steve
While you could use two layers of vapor barrier you could also be creating a problem for yourself if you have a claim. Swiftlock is an Armstrong product. Precision Components brand underlayments are produced for Lowes by MP Global Products. You can contact MP Global Products at 402-379-9695 | 1-888-379-9695 | mwp@mpglobalproducts.com to discuss the particular cushion you purchased and ask for their recommendations.
Terry
I have approximately 1800 sq ft of laminate flooring in my house. It is installed on a concrete slap (37 years old) with a vapor barrier and foam backing. For 6 years I have not had any problems. Recently in my hallway the edges of the floor started swelling up. I pulled up the flooring and found a considerable amount of water on top of the vapor barrier. Underneath the barrier was dry. I removed the vapor barrier and for 3 days looked for any signs of moisture and didn’t find any. I layed the vapor barrier back down without the flooring and in less than 24 hours looked underneath it and once again it was wet. The air conditioner/Heater intake is in the hall close to the floor but the first signs of swelling occurred about 4 feet from it. I live in East Texas and we had an extremely hot and dry summer. When I noticed the problem we were running the air conditioner and heater depending on when cold fronts came through. I appreciate any suggestions or comments.
Brent
What we often refer to as vapor barriers would be better referred to as vapor retarders for while they reduce the passage of moisture the vapor will still pass. Vapor barriers have different perm values so the amount of vapor transmission is partially dependent upon the value. Even old concrete slabs can suddenly have moisture concerns appear. There can be a variety of causes for the problem you are seeing such as dry air in a living space acting as a “magnet” and pulling up water vapor that is migrating up through the concrete. If the air is dry enough you may or may not notice the moisture build up on the concrete or may see it on part but not on other parts of the concrete. You can also experience top down moisture build up on top of a vapor retarder.
A situation such as yours will usually require an onsite inspection and testing to truly know what the cause is. You can find very good inspectors near your area listed at nicfi.org
Good luck, Terry
I have seen people install the vapor barrier and laminate flooring without removing the baseboards. Most recommendations for installing the vapor barrier suggest running it up the wall a couple of inches which will be covered when reinstalling the baseboards. How should the vapor barrier be laid if I choose to leave the baseboards in place? Thanks!
Melissa
If you leave the baseboard in place you will have no choice but to run it up to the baseboard or slightly under the baseboard if elevated. If the floor fails due to vapor from the concrete it may not be covered by the manufacturers warranty for the vapor barrier was not properly installed. Also, if the baseboard is not removed you will still need to leave the required expansion gap for your laminate floor and this will need to be covered with a quarter round attached to the baseboard. If the floor was being installed in my own home I would chose to have it done properly with the baseboard removed and the vapor retarder properly installed.
Terry
Two years ago, I had the kitchen completely ripped out and remodeled. Custom on-site cabinets (solid birch) were built directly on the slab. A vapor barrier was put down, and laminate wood floors were installed. The bottom cabinets have begun to mildew and rot. Some are so soft, I can push a finger through the wood. We have had plumbers out to test for leaks in the slab, and they were unable to locate a leak. I can look under the vapor barrier under the stove, and it is wet. Not moist….wet. Before the remodel, there was ceramic tile in the kitchen. Can changing from tile to laminate cause the moisture problem? Is the moisture under the vapor barrier escaping to the cabinets causing the mildew? I’m out of people to call about this problem, and no one can tell me why its happening. Please help! Thanks!
Adam
We hear this all the time that a plumber was unable to find any leaks and yet there is or has been a leak. Often the leak is a slow drip in a wall or under the dishwasher or sink. Sometimes a leak stops for some reason and the areas dries. Look under your dishwasher and run it through a full cycle checking for a leak as sometimes the only leak is while the dish washer is running. While it could be moisture from the slab the fact that it is making your cabinets soft makes me question that. If you don’t find a dish washer leak my suggestion is to have an Independent Flooring Inspector perform testing to determine the cause. Inspectors such as my company The Weinheimer Group can be found for most states at NICFI.org
Terry
I installed some laminate on a slab over a preexisting glued down engineered wood floor
I put vapor barrier over the engineered wood. Since then the vapor barrier has trapped moisture in the engineered wood buckling it and cause the laminate to buckle. This has only happened in 2 places over about 1000 sq ft.
Should I remove the vapor barrier or go down to the slab and relay the laminate on the vapor barrier?
You have given a lot of great information. But, I have a question I don’t think you have answered. We installed laminate floors throughout our entire home in Florida last year. We foolishly did not install a vapor barrier. We did not think we needed one with the padding that came attached to the laminate. WRONG! We now have peaking on many boards and the laminate has run under the baseboard molding. We removed the quarter round molding and cut away the extra wood. We have pealed back all the floor in the kitchen, sunroom, living room and dining room. There is a mildew smell on the foam backing and in the room now. Can we rescue the floor? We purchased vapor barrier and will wash the foam backing with a bleach water solution. Will the floor peaks go back down? Is there any hope for this project? We worked so hard on it and want it to last another 3-5 years when we will do some kitchen remodeling. Thanks, Karen
I forgot one more thing. Should we get the vapor barrier with the soundproofing on it or just the plastic?
Brian
With the engineered floor being buckled you will probably have no choice other than remove it prior to reinstalling the laminate. Laminate floor needs to be installed over a reasonably flat surface. When most laminate floor is installed over concrete you need to you need to use a vapor barrier. Installing floor over wood you usually only need to use a cushion. Check the manufacturers installation instructions for the product you are working with so you will no what their requirements. For most laminate flooring products the installation instruction can be found on line.
Terry
Karen, It sounds like you have experienced quite a problem. Hopefully you have now reviewed the manufacturers installation instructions for the product you are working with. Make sure you are using the type of vapor barrier they require before going ahead with the re-installation.
You say there is a mildew smell on the foam backing and ask if you can rescue the floor? Possibly you can but there is not a guarantee. If you spray or wipe down the foam on the back of the planks use very little moisture. If you use too much moisture you will only add to the problem. If you have a flat open area that is large enough to spread the planks out than do so. If not you will need to stack your planks in a way that they can dry for several days prior to installation. The main problem I see with stacking is that the foam should be dry before stacking. In a week or two you should find out if the peaks are going to go back down.
If you perform the cleaning and drying in another areas such as a garage – prior to installation be sure to acclimate the product in the area of installation for several days before you install it.
Terry
Karen
Adding sound proofing dose help to remove the clacking sound often heard when walking on a laminate floor. If the manufacturer of your flooring product approves of the vapor barrier with a sound reduction system added it sounds like that would be the way to go. You can Google the manufacturer and find the phone number for their technical department and give them a call. If you can’t find it let me know.
Terry
Hi I installed laminate flooring about five years ago, I used the proper type of vapor barrier for concrete, I find now that I am starting to get some warping on the cut ends of the laminate that are next to the 9ft slkiding glass door that I have. The thing that throws me is that I have another 9ft sliding glass odoor and I have no problem with that one. On the outside of the house I have a concrete patio (it sits lower that the slab) and whenever it rains it stays wet at the corners where I am having the problem. I’ve had the contractor nad he said it might be that the laminate is absorbing moisture from the outside. any ideas?
After installation of a laminate floor…what makes the floor look buckle in some areas, and what causes a cracking sound when you walk on the floor?
Thanks!
Velia
There are a number of things that can cause the cracking sound. If a newly installed laminate floor is also buckling the first thing that I would do is to make sure the floor is not locked in. Lock in can be the failure to leave enough expansion space around all walls and fixed object; nailing through the floor when the baseboard is installed; nailing, stapling or screwing transitions through the laminate or even installing counters on top of the laminate and attaching through it to name a few. Any time you are doing something to stop movement of the laminate including not installing the proper transitions between areas can result in buckling. Another common cause is moisture especially when installed over concrete. Besides crackling being related to the buckling or lock in it can be related to a floor that is not flat, cushion below the laminate not properly placed, a product problem or with some products it just takes a bit of time for the laminate and cushion to make a good marriage before the crackling stops. While these are more common causes we do find others.
Terry
Hi Terry,
I was wondering if you can help me with a question we have. We just finished installing laminate flooring over ceramic tiles in the basement and we had a hard time avoiding gaps between the planks. We are worried that we did something wrong. The laminate flooring came with the underlay already and we did not put a moisture barrier before installing the laminate floor. Did we need the moisture barrier? We did the installation twice because we didn’t like the gaps the first time, and still we see gaps the second time…this is a nightmare! could you please help us?
Thanks!
Alex
Alex
Installing laminate over ceramic tile needs to be treated like installing it over a concrete floor and this would include the use of a vapor retarder. (moisture barrier). That being said does the product you installed consider their attached cushion to be a vapor retarder or do they say to use one below it?
As far as the gaps go ceramic tile generally has high and low edges. You need a smooth surface for laminate flooring and often the only way to achieve this is to float a leveling compound over the ceramic tile to make it smooth.
Gaps can also be left when you are joining a plank and not getting them to properly click together. Many laminate flooring products require that you use a tapping block in addition to just clicking the planks together.
Unfortunately you are just going to have to live with the gaps unless you replace the floor again. Only time will tell if moisture is going to damage the floor without a separate vapor retarder.
Sorry for the bad news as I am sure this is not the type of help you wanted.
Terry
hi sir .. iv recently installed laminate flooring in my lounge .. iv noticed i n some areas the planks are not level with each other.if you run your finger across the the boards wher the boards are clicked together the one plank is slightly higher than the one next to it.. can u give me possible answer .. floor is level as it was screeded before installation..
thank u
i kay
With laminate flooring you may notice a bit of height variation (ledging) where one plank meets the other. The North American Laminate Flooring Association Standard for NALFA members is 20 mm (0.80 in) as listed in NALFA Standards Publication LF 01-2011. This standard is proprietary with many laminate manufactures so you can expect a different allowable height variation from some.
Terry
Hi,
I had a professional install a floating floor over my existing plywood flooring a couple of years ago. He used a foam underlayment with a moisture barrier.
Now as I am considering doing the rest of my house with floating floor, I went under the house to inspect the flooring from underneath, and all of the area that has the floating floor on is thick with mold (underside of the plywood).
Now I don’t know whether i should put floating floor in the rest of my house. Although the rest of my house is floorboards (dry), I do not want to ruin them by trapping moisture under there.
Admittedly the area with the moldy ply wood is the closest to the ground (approx 40cm to 1metre ) up under the corner of the house on a hill, so it would stand to reason that there would be a higher degree of moisture there, however it is quite open with no walls around the higher side. I have lived here for 15 years and have never seen mold under there before now. But I do now wonder if this plywood has replaced rotting floorboards previously.
So the question is : If I replace the floating floor and ‘not’ use moisture barrier as you suggested for wood. Should I also replace that whole moldy section of plywood, and then am I going to have a problem of the moisture coming up into the house and into the new floating floor. ???? I’m worried about the health issues of having mold under my floors as i do family day care in my home.
Thanks heaps, I hope you can suggest an idea for me, I’m at a bit of a loss of what to do.
Wendy.
Does having the vapor barrier on concrete pose a threat for mold to grow between the concrete and vapor barrier because of moisture?
I recently had laminate floors put in on a concrete slab in a house. On section buckled and the people who installed it said I have a moisture problem. I have had it checked for a slab leak and there is none. I see nor feel any water on the floor. Is there a way to check the floor to see if there is a moisture problem? thanks- Sonya
Wendy
Mold is something you do want to get rid of and yes I would suggest replacing that section of the plywood. I would suggest you visit the following US Government site where you will get some helpful information on Mold and treatment for it. http://www.cdc.gov/mold/stachy.htm
When installing a floating floor over a wood substrate you use a foam or other approved underlayment under the floating floor it is generally recommended that one be used that is without a moisture or vapor barrier. Vapor barrier (moisture barrier) is used over concreted floors unless otherwise required for a particular product.
Terry
Carrie
A proper vapor barrier should not pose a threat for mold. I would suggest you visit the same US Gov site I suggested to Wendy in a previous reply. You will get a lot of helpful information on mold. http://www.cdc.gov/mold/stachy.htm
Sonya
There are several ways to check the floor for moisture. The first and easiest check is to take a clear sheet of plastic about a foot or thee feet square and tape it to the concrete with duck tape. Wait at least 48 hours to remove. If there is high moisture the concrete surface will dampen and you may see droplets of water. Flooring inspectors and your better flooring contractors will have a concrete moisture meter. With this meter they can identify high moisture. More accurate tests include Calcium Chloride testing and in slab relative humidity testing which many flooring inspectors and some flooring contractors can also perform for you.
Terry
You have not quite answered my question from other peoples questions. I am installing a laminate with a foam backing (dream home) over a old parquet in a condo with concrete floors (7th floor). a sales person said I should use a sound suppressant underlay which has a vapor barrier in it. Another person said not to as I would get too much bounce which would cause the joints to wear and slip. What is the answer?
Janice
Is there a such thing as laminate touchup kits? for dents, dings, or scratches? Where do you get them without ordering them off the internet?
Janice, If it were me I would not use an additional cushion when the laminate has an attached cushion. I would use the recommended vapor barrier for this product which is DREAM HOME 6 or 8-mil plastic sheeting film. I would also call the Dream Home toll fee number for Customer Care or Technical Support and ask them what they would recommend and guarantee the installation over. The number is (1-800-366-4204)
Terry
Aaron
At most building supply stores you can purchase putty type sticks that come in a variety of colors and are used to patch wood and would be useable on most laminate. As far as laminate touch up kits I personally do not know of a source other than over the Internet. You might try one of the big box stores such a Lowes or Home Depot or perhaps one of our readers can suggest a source.
Terry
Terry;
Can I use rosin paper or black tar paper over plywood flooring for my laminate flooring ?
Johnny
Johnny, you can use a black flooring paper but that does not mean the manufacturer of your product will warrant the floor if installed over it. Call the manufacturers technical department for whatever product you have.
Hey there! I could have sworn I’ve been to this site before but after checking through some of the post I realized it’s new to me.
Anyhow, I’m definitely happy I found it and I’ll be bookmarking and checking back frequently!
Hi Terry I am planning on installing a cork enginenered floor over a concrete heated slab with a moisture barrier under the slab should I use a moisture over the slab also if so can I use felt paper or some other product. Please help if you can Thanks Roland
Sorry Rolland but this site deals with laminate questions. I strongly advise you to call the technical department of the product you want to purchase and discuss it with them. The requirements can be different between manufacturers and you do not want to void your warranty.
Terry
I have three bedrooms off a hallway that I wish to install a Tongue & Groove engineered wood flooring product over a concrete slab. The hallway has bamboo floor intalled over ceramic tile. I don’t know who the prior owner was who did this, but the bamboo floor has held up rather well so I don’t want to remove it. The problem is that if I install the engineered wood in the bedrooms I will need to install a plywood sub-floor to boost the level of the bedroom floors so they are even with the hallway floor. I have purchased a sound-barrier. My question is: after I clean the concrete slab and apply leveling compound do I put a palstic vapor barrier down first, before I install the plywood subfloor? Where does the sound-barrier go? Does is go between the plywood and the concrete? Of between the plywood and the engineered flooring?
The vapor retarder goes on the concrete and your sound control cushion usually goes between the floating engineered floor or laminate. A vapor tests should still be made on the concrete to make sure it is within limits for the flooring being installed.
My son installed an engineered wood floor in my condo several years ago. A small area of the flooring has some dark spots on it caused by a water leak from my dishwasher. I cleaned up a small area of mold on the wall just above the moulding and quarter round and in back of the dishwasher. My question is, since we installed a moisture barrier, do we need to take up the flooring with the dark spots to ensure there is no mold and if so what is the purpose of moisture barrier if you have to remove the flooring anyway when you have a water leak? There is no buckling just that the wood flooring in two small areas have dark spots on them but the flooring appears extremely dry. We pulled up the quarter round in the area that may have gotten wet but it all appears extremely dry. In other words, my question is….does the moisture barrier serve to prevent mold under a floor that most likely got wet from the dishwasher leak? Thanks!!!
We are going to put Fossilized bamboo flooring from Cali bamboo in our living room and hallway. What is the best vapor barrier to use and it will be over concrete above grade. The house has carpet now and we have never had a moisture issue.
John, Here is a link to the Cali Bamboo Installation Instructions. It is always best to stay with the requirements for the product you are using. http://www.calibamboo.com/mm5/pdf/installation_guides/cali_bamboo_flooring_installation.pdf
I’m not sure if this has been answered yet but I’m putting laminate floor on a wood subfloor. The kicker is its over an entry over hang and in the winter the floor tends to be cloder in this area. Should i put a plastic vapor barrier on this area of the floor? Or will this cause damage to the flooring and/or the subfloor?
Note : i have insulated the overhang some but it may require more to completely stop the temperature changes on the floor.
Thanks for listening
Josh
I am putting a floating floor in a bedroom. When I try to put the underlayment down it starts bubbling up after I get a few staples down. How can I eliminate these bubbles or should I try another type of underlayment? Foam density is 5.5#. Foam thickness is .115.
Home Depot is putting in new laminate floors in a week or so. I’m pulling all the old laminate up. There is a felt/plastic pad under the old floor. When I pulled up the felt the concrete was wet underneath and had a mildew smell. These floors were down before we moved in 4 years ago. The A/C was replaced a year and a half ago and the carpet used to feel damp b/c the old A/C was not controlling the humidity. Is this moisture from a year and a half ago when the A/C was not working? Or is there another issue?
More info. The felt was over concrete floors. We are bleaching the concrete now.
We are installing a Lumber Liquidators laminate floor over a old linoleum floor glued to a concrete floor in the central California Coast. Is a vapor barrier necessary for this instillation? We removed a 1980’s carpet and found the linoleum floor. The floor is original to the 1979 track home, the visible glue is black
Hi, I’m getting ready to lay a Mohawk heirloom with attached pad. I’m putting it on a particle board sub, thinking about putting down felt paper for more warmth. Is there any problems with attached pad and felt paper being together and floating? Thank Tom
Hello. I am researching the installation of laminate flooring in 1 section of my basement and carpet in another section. Every site I have found states that i need a vapor barrier under the laminate, and every site I read about carpet says to never add a vapor barrier underneath because mold and mildew will form underneath it. Very confused. Does mold and mildew form under the vapor barrier or not? is it a problem if it does? Does the laminate vs carpet make a difference?
Carpet breaths much better than laminate and therefore while a concrete must meet the manufacturers moisture requirements a vapor retarder is rarely used.
For laminate a vapor retarder is required for most when installed over concrete. As far as mold forming under the vapor retarder, it can occur, not normal for it to and that is not the reason one is not used under carpet.
Terry
Usually not, but always read the manufacturers installation standards first.
Terry
That depends on the manufacturers requirements. Check with the dealer.
Hey Terry, you sure know your lam flooring. I have 7 year old lam, in good condition, over a conditioned crawlspace and no mold or mildew problems anywhere. I had never cleaned the floor, only vacuumed so it was very dirty and last week I wiped it down with a damp (not wet) rag of Mr Clean and water. Now I have a very strong musty smell coming from some areas. Any thoughts? Thanks.
I am considering installing laminate in my dining room. This would be the scenario: the concrete slab has plywood laid over it (why I don’t know), and there is linoleum glued to the plywood. Vapor barrier or no?
Mark
I have ran this by a number of my colleagues and none of us have been able to come up with an answer for you. It is our suspicion that the “strong musty smell” has another cause other than wiping it down with a damp rag using Mr Clean.
The linoleum under the plywood should serve as the vapor barrier (retarder). Usually you don’t want to use a vapor retarder over wood but since there is concrete below the plywood the flooring manufacturer may require it. My suggestion is for you to call the technical department of for the laminate product you want to use. If you have a problem finding it listed on the internet, contact us and we will try to get it for you.
Terry
Hi, my fiancee and I just took out all of the laminate flooring in our house. The bedrooms had concrete under the laminate with a thin moisture barrier (the rest of the house had tile underneath the laminate). However, we happened to find mold under the laminate in two of the bedrooms even though there were no signs of mold anywhere and the laminate had not ever buckled or warped. The laminate was put in about 4 years ago. There is also no visible signs of any leaks. The installers are not willing to install the new laminate (which we already bought) because of a high moisture level reading in the master bedroom only. The installers will however install tile in the whole house, including the master bedroom. So now we are in a major pickle because putting tile in the entire house is going to cost over double what we were planning on spending (plus having to remove the original tile in the entire family room and kitchen before putting in the new tile). We would rather stick to the more economical laminate flooring than tile but we are afraid that if we put in the new laminate we bought, the mold will return and it can become a health issue for us and future children. Is there anything we can do to prevent mold from growing underneath a new laminate flooring? What is your suggestion? THANKS!
Meagan
Sorry that you have mold. There are many types of mold and some are very dangerous. Sorry, but I cannot offer advice on how to prevent its growth. You might like to visit the Center for Disease Control and Prevention website. Here you will find a lot of helpful information.
As far as installing laminate where you have excessive moisture in concrete, I do not recommend that. Check the technical department of the manufacturer that supplies the laminate you purchased. You should be able to get their contact information on the internet. The manufacturer will let you know what their limits are for concrete moisture. Also if you put tile in, many of these also have limits so you need to check those out.
Good luck, Terry
Hi! I had laminate installed a couple of months ago. I’ve been stubborn about turning on the air conditioning this early in the year and had the windows in my bedroom open. The last 3 days, it has been pretty humid. I discovered a place in my hallway outside my bedroom where two planks have peaked. You wouldn’t notice it by looking, only when you walk over that area in the hallway. I have no reason to suspect a water damage issue. I’ve since turned the air on to get the humidity out of the air. Will that solve the problem on its own?
Stephanie, it sounds like one or more planks may be installed tight at a wall or other fixed object. Or the laminate travels through the doorway without a transition between the rooms. Either one of these can cause the floor to move up and down with an increase in relative humidity. Using the air conditioner will lower the relative humidity and may take care of the problem. A more permanent correction is to add expansion space or a “T” molding if needed.
Terry
Hey Guys!
I’m thinking of having a (radiant barrier/thin foam insulation) sheeting installed on the underside of my 2 x 10 floor joists rather than fill between the floor joists with fiberglass batt insulation. The insulation in question has a foil face on one side and a white face on the other. The foil face is to face upward and the system has a .047 perm rating. Am I asking for mold/condensation problems beneath the floor system of my raised home. The finished floor is a beautiful pine tongue and groove and I live in New Orleans where temperature and humidity are off the charts year round. Your input would be greatly appreciated. Thanks!
Brent
You would be best to ask this question of one of your local building inspectors. From my perspective I would not think it to be a problem as long as your crawlspace remains dry and you maintain good ventilation.
Tery
I live in a walk up apartment building to where I understand that the building was made 30 years ago and it was made on top of a concrete slab. After the concrete was done the builders put a water barrier (don’t know what kind. Then they applied almost like a chip board on top…then applied under lay for carpeting. I know that most of your questions has to do with laminate flooring but I would like to know if you knew about my concern. Back a month ago I had cleaned my carpets and one room took a lot longer to dry. I noticed about a year ago when I changed this room around that the leg of the bed was indented in the carpet…I noticed as well that around this indent I can feel and actually hear cracking. On the side of the building, more or less where there is a broken easedroft. Could this be happening because of moister and could there be mold growing in this room?
Terry and Kevin, would you know the answer to this. I lived in this building for just over 5 years and after 2 years I’ve been identified with a mental disability. All my children do not get their proper sleep and they actually take a sleeping aid natural pill.
Please Oblige….Thank you very much
Chrissy
Crissy, thank you for your question. Our sister site where we handle carpet information is Carpets Wall to Wall. Anyway, you ask if the crackling sound might be moisture and if you might have mold under the carpet. If you feel that there may be something wrong that is causing health problems you should have the area checked by a certified carpet inspector or other expert that can tell you if there is a moisture concern. There are also experts that deal with mold.
If you cannot feel any moisture under the leg of a bed or heavy piece of furniture in an area where you hear the cracking sound it probably isn’t moisture. This sounds more like a carpet pad issue or a concrete coating breaking down instead. If you don’t have moisture than it is doubtful you have mold. You might want to peel back the carpet in a corner of the room or a closet and see if this tells you anything. Your best advice though is where there could be a health issue, have it checked out by the experts.
Terry
Thank you, Terri and Kevin for responding to the question with me seeing your blogs on your site it made me reach out to someone about this issue. It had been 4 weeks that the super did not get any word from the manager to do anything about this issue yet…seems that I will have a fight on my hands if it does not get looked after soon.
Please help,
I am installing the moisture barrier under laminated 15 mm floor over concert on the second floor apartment. The moisture barrier is 3.5 mm thick. Many websites instruct overlapping them around 10-15 cm, some others say Never ever let them overlap. I laid them overlapping each other at the edges and I got around 3 mm bump across the room. Can I now safely lay the laminated floor over this bump or I need to trim the edges of the underlayer so that they don’t overlap and there is no bump a all?
I desperately need your advice before I can go on with installation of the floor.
Thank you for any comment and idea
I have purchased laminate flooring with the foam back attached to it. This will be installed in our cottage over wood subflooring. The cottage has an 18 inch sand crawl space which we had a 10 ml vapour barrier put on top of the sand and wrapped all of the pillars and 8 inches up the sides as well. Then we had spray foam insulation to cover the rest of the exterior walls (over concrete blocks) up to floor joists. There is no outside ventilation in crawl space now (have considered running a fan down there though to ensure it does get ventilated). We had one gentleman give a quote on installing laminate in the cottage and he suggested we put 6 ml vapour barrier over plywood subfloor even though the laminate has a foam back to it. I am concerned that moisture from the crawl space will seep into the plywood subfloor if there is another 6 ml vapour barrier on top of the subfloor besides the foam back on the laminate. Not to mention the noise of the 6 ml under the laminate possibly. Any suggestions?
Overlapping will give you better protection. The other alternative is to tape the seams. If you do neither the result is an open void between the joined sheets. It is always best to check the installation instructions for the manufacturers flooring you are installing. Most require flatness of a floor to be within 1/8″ in 6 feet.
Linda, It sounds like you have done your homework. It is not a good idea to use a vapor retarder over a wood subfloor. The foam backing on the planks is okay. Whatever you can do to ventilate the crawlspace should be done.
My girlfriend had water damage in her home back in November. A contractor came in and replaced the damaged flooring with 3/4″ plywood and 1/4″ plywood Underlayment. Not sure what the Underlayment under the actual laminate floor is, but it looks kind of like tar paper. Now, only 9 months later, the floor is buckling and the 1/4″ plywood is lifting at the seems. Obviously a moisture issue, but I’m wondering if it is being caused by whatever Underlayment they used!!?? The contractor is saying it’s not his fault.
Josh, the only way you are going to know what the problem is for sure, is to have the laminate flooring installation inspected and tested. The inspector should be able to verify what was actually installed and check moisture levels. It could be related to the vapor retarder but there is an excellent chance it is related to either excessive moisture that was still in the floor, a new moisture problem or something else.
Terry and Kevin
When plywood, laminate or tongue and groove wood is placed on concrete there should be a vapor drive test performed by taping a small area with poly sheeting for a day or so. If there is condensation forming beneath the poly sheeting then something should be done to seal the surface of the concrete floor. Check with a professional to see what product is recommended to seal the surface of the concrete floor. Vapor drive is more intensive in an air conditioned environment. Remember hot goes to cold and wet goes to dry, and the greater the difference in temperature of the slab and the indoors air temp, the greater the vapor drive. So many things can be causing the unchecked vapor drive such as the water table beneath the slab and the integrity of the poly vapor beneath the concrete slab. Bottom line… water damaged floor due to vapor drive has to come up and most times there is mold associated with the water content in the wood. Be careful to have professional mold remediation performed if such is the case. Also be sure that any new flooring must be placed in the home, unpackaged from cartons and allowed to reach indoors equilibrium in temperature and water content in the wood. GOOD LUCK!
I live in Pittsburgh, PA and 7 years ago built an 11’x22′ unheated sunroom over our unheated garage. The floor of the sunroom/roof of the garage is 8″concrete over 30 yrs old. It was waterproofed during construction. I installed a Dricore sub-floor about the same time. Of the 4 walls, one adjoins our family room with a slider-door, one faces north with 5 double-pane windows, one faces south with 3 double-panes and one faces west with a slider door and 2 double-panes…but this side is covered with an extended roof so direct sun only effectively enters the narrower south side. All walls and ceiling are insulated. Gas was installed for a wall-mounted unvented heater (yet to be connected. Why the details? I desire to install laminate flooring but am concerned with: 1) vapor barrier or not?…Dricore has rubber on the bottom and OSB/Waferboard on top. Dricore says its permitted as long as the vapor barrier stops at the sub-floor edges. 2) temps…while the room is currently unheated, the wall-mounted heater was planned for occasional winter use and was installed as there was no easy way of ducting the house system to that room. I’ve been reading that laminates may have min temp limits that our area could exceed during the winter months. 3) dogs and cats, yup got ’em and am very concerned with, ah, leakage as they are getting older. I’ve been impressed with the Konecto Prestige planking installed at our vets office years ago…but will it work in my application? And the general question, if not laminate, then what other recommendations would you make? Thanks for any assistance and I echo what numerous others have stated, this site if very informative!
Al,
Thank you for the compliments regarding the website. In regard to your concern, neither a laminate plank flooring or a vinyl plank flooring are going to be a good choice for you. While a vinyl plank such as the Konecto Prestige you mention will give you better performance under some of the conditions you describe it will not perform well under others. You will need to take some serious precautions to make it work.
Konecto does not recommended the product for use in sunrooms. Direct sunlight may cause Konecto to fade or the grip-strip to separate. With these conditions you would need to use window treatments and the room would not longer be a sunroom.
You mention pets urinating. While urine will clean up easier on a vinyl plank and will damage it less than a laminate plank, Konecto states in their maintenance manual, ” Do not subject to standing liquids including pet urine.”
Even with your gas wall heaters, maintaining proper temperature an humidity in this room may be a problem. Konecto states in their warranty, “This Limited Warranty is void if, prior to installation, this flooring is not acclimated to room temperature (between 65°F and 85°F) at job site between 24 and 48 hours and, if post-installation, such flooring is not continuously maintained at such temperature.” What happens with too much or too little heat and humidity is excess expansion and contraction which can result in the planks pulling apart.
The above are just a few of the issues that you would need to address with the Konecto and the restrictions are even more severe with a laminate plank.
My personal choice for a room such as this would be ceramic tile or stone.
Terry
Wow, I sure do appreciate the thorough and detailed response, far exceeded my expectations! Sure wish u guys were located in the Pittsburgh PA area as u’d be my first choice for my upcoming shopping. In that regard, if u have any business contacts in this area I’ll go to them first but if not, thanks very much again.
You are certainly welcome, hope all goes well! There are a lot of excellent floor covering stores and we stay away from making recommendations to a specific store. My suggestion, go to the World Floor Covering Association website and click on the Find a Store link. Usually these members are good reliable companies.
Terry
Hi Terry,
I recently purchased a house on a concrete slab. It was built in 1959. Upon pulling up rugs, the majority of the house has 9×9 Asbestos tiles. They’re in good shape. I plan on going over them.
Most of the rugs/subfloor padding were Ok- Some had slight dampness in small areas. However, my master bedroom subfloor was much more damp and moldy throughout. I’m not sure if it’s a leak off of the master bath, or if concrete can “sweat” that bad.
My question is: Should a vapor barrier be used on top of the asbestos tiles for pergo flooring? The pergo flooring does have built in pads, but I am wondering if a vapor barrier is necessary. Some people are saying the asbestos tiles act as the barrier. What are your thoughts?
Dan
If you have dampness, the cause of it needs to be determined prior to installing a new flooring. If you have a plumbing or other leak this would eventually damage a new flooring.
In regard to a vapor retarder you will need one for your Pergo floor. Pergo installation instructions state, For flooring installed on all concrete subfloors
that emit a water vapor no greater than 5lbs/1000sq. ft./24 hrs,including those covered by tile, vinyl, linoleum or sheet flooring, you must use a non-recycled (100% virgin) resin 6-mil (0.15mm) with a density of 0.92lbs/cubic ft. and a thickness tolerance of +/–10% polyethylene film as a vapor barrier.
Hope this helps, Terry
Amazing Q&As here! Thank you so much for sharing your technical expertise!
We have a basement that is carpeted. One bedroom has a moldy smell in the carpet that we believe was caused by carpet cleaning right before the house sat untenanted over a wet winter (we live on the Northwest Coast). Our plan is to remove the carpet, treat the concrete floor with Shockwave Antifungal, and then paint the floor with Zinsser Watertite to seal against any possible external leaks. This advice was given to us by a mold remediation company. We are installing laminate, so do we still include a vapor barrier? Or does Zinsser Watertite serve as a vapor barrier? The mold remediation company said that traditional vapor barriers can cause moisture to travel up the walls and cause mold in the drywall, so he doesn’t recommend them. What are your thoughts?
Thank you so much for your help!
Rose
Why can’t concrete sealers be used instead of vapor barriers for laminate flooring?
Rose, There is an ongoing debate about the use of vapor barriers (retarders) being used on studs. Some feel that when vapor barriers are used on walls they will hold moisture and cause mold. Others believe that especially in cold weather areas vapor barriers are important on walls. As far as vapor barriers on concrete causing mold in walls, in my many years in the industry have never experienced that. As far as a floor seal taking the place of a separate vapor barrier or retarder you would need to contact the manufacturer of the flooring product you choose to install. Most flooring manufacturers will void your warranty if you do not use a vapor barrier or vapor retarder that they approve of.
Terry
Bill
There are many types of sealers and some will do a better job than others at reducing the passage of moisture from the concrete into the laminate. Flooring manufacturers make it a practice to require the use of a vapor retarder or vapor barrier over a concrete slab. If you fail to do so and a problem develops with your laminate they void your warranty. As I told Rose in the previous comment, you can contact the manufacturer and see if they will approve it. Check our directory for the number. If you do not find one, go on the internet and look up the Technical Department for the product you want to use or feel free to contact us and we will add the number to our directory.
Terry
I work for a large home builder and am the warranty rep for several communities. We have numerous problems with laminate floating floors. Most of the visual problems are that the butt ends of each piece are buckled upwards/looking across the floor it looks buckled between each piece/each piece sits higher than the other creating a sock catcher and the butt ends are puckered at one side or the other. These are installed over gypcrete and concrete floors. Both are dry. These floors look like this the day after installation. There is also springing that shows up anywhere from a day to several weeks after the install. I also have prefinished hardwood floors installed over gypcrete that sound like an old bar room floor from the cowboy days after a few months. Creaking /cracking and popping. What is the proper vapor barrier that should be installed between the flooring and these substrates?
Common Sense,
You have a great user name and it sounds like you are using it for you ask a good question. You do not say what laminate flooring product you are using. One thing they do have in common is that laminate floors will expand with moisture. It sounds like you recognize that you are probably experiencing expansion which can result in both end peaking and deflection which you often hear as creaking, cracking or popping.
Regarding vapor retarder under laminate flooring I would encourage anyone installing laminate flooring over gypcrete, concrete or any other surface to read the installation instructions or call the technical department for the product as vapor retarder requirements do differ among manufacturers. Here are a few examples:
-Shaw, 6mil-polyethylene film, below and above grade.
-Pergo, 6mil 100% virgin non-recycled, alkali-resistant polyethylene film, over any grade subfloor.
-Kronotex 6mil-polyethylene film over concrete thought they say use best underlayment that meets jobs budget, however do NOT use an underlayment if the product already has a pad attached. -Mannington, Whisper 3N1.
-TORLY’s, TORLYS brand.
-Columbia, Mohawk, Quickstep, Unilin, 2 mil moisture barrier polyethylene foam.
Regardless of the vapor retarder be sure to follow the manufacturers moisture testing requirements even if the concrete appears dry.
Terry
I’ve recently purchased 10 mm thick laminate with foam backing. My installer wants to lay that over my vinyl flooring that is now cracking and lifting up. This vinyl flooring is on top of concrete and will be replaced in my foyer , hallway, bathroom and kitchen. He is telling me that it is ok to lay down the laminate over it without the quiet Walk floating floor underlayment . My question is will it be ok to install without the underlayment and over cracked, lifting vinyl?
Marilyn
For me to answer your question I would need to know the product that you plan to install. Not all manufacturer requirements are the same for laminate flooring installations. Some may allow you to install their floor that already has a foam back over an addition underlayment. Many would not has you already have a cushion on the back of this laminate. My advice is to go on the internet and read the manufacturers installation standards for the laminate product you plan on installing. If those do not answer your questions call the technical department – number should be listed on website – ask them. If they will not help you get back to me and furnish me all product information and I will reply to you here in the comment section.
Good luck, Terry
Hello,
Why can’t laminate be installed over hardwood floor that’s been glued to a concrete subfloor? Also, is it possible if a vapor barrier and laminate are installed over such a floor, it would trap the moisture and cause the original hardwood floor to buckle when it wouldn’t ordinarily with no change in the amount of moisture coming from the subfloor? I have a condo in Arizona that I am having issues with and that is my suspicion but I’m not an expert. Any insight would be appreciated! Thanks!
Angelina, you have done a great job in answering your own question. Thanks for sharing!
Terry
I’m installing laminate flooring in a 50′ x 25′ foot room (basement, concrete floor). I’ll leave about 1/2 gap around the edges of the room. Will I need additional expansion joints in the room. I read somewhere that rooms over 27′ require additional expansion joints.
Thanks
Norm
We had to remove our old pergo flooring as it was bubbling. The flooring was very old, probably 15 years since it was already here when we moved in. We removed the old flooring and found moisture and puddles of water. Most of the water smelled like pine sol or other cleaning solution and appeared to be a soapy type consistency. But we were also concerned with our dishwasher since it was also old, and found it had a small leak. We think a combination of the leaky dishwasher and our poor cleaning methods created the warped laminate. We are now in the process of laying down some new laminate over the concrete slab. We have installed the vapor shield/underlayment, the kind with the small foam balls, and 24 hours after we laid it down we went to inspect the flooring before we laid down the new laminate. We found there was still some moisture. Is this somewhat normal for concrete thus the reason for a vapor shield? There is no leak anywhere, as soon as we removed the underlayment the area dried immediately. The weather in the Southwest US has been a little wetter than normal. Our thoughts are that the ground is saturated and it could be coming up through the concrete. Our concern is it ok to go ahead and lay down our flooring and expect the vapor shield to do its job? Or do you have other suggestions?
Norman
In a large room like this, especially over concrete you should leave additional expansion space, at least 3/4″ and make sure it is left around all fixed objects. As large as this room is you may still experience an expansion problem. Consider a T type transition about 1/2 way through the length of the room. Even more important, contact the technical department of the manufacturer for the laminate you are installing. Ask them for their rec recommendations ask that they email the recommendations to you, follow them to a tee and hold on to the correspondence in case there is a problem later. Since the floor is over concrete make sure you adhere to there required testing and when the floor is tested write the test results on the concrete so that if you ever have a problem you have proof of what the moisture was prior to installation.
Best to you,
Terry
Marilea
Even if a concrete is old and even if it appears dry on the surface, the moisture level within it can still be too high for many flooring products. Each manufacturer sets its own moisture standards and most require that you test the concrete moisture level prior to installation. While the moisture you saw and smelled sounded like it may have been from the problems you described, some of it may have been from the concrete. I would not complete the installation until you have tested the concrete based on the standards of the manufacturer for the product you are installing.
Hope this helps,
Terry
I found your site while looking for answers as to whether or not I had to use the small/expensive 6mil plastic underlayment rolls @ 16 cents/sqft or if I could use the giant bulk rolls at ~5 cents/sqft. Now I’m really confused after reading some of your advice, but you sure seem to know what you’re talking about! The flooring I’m trying to install is laminate, specifically the 8mm Harmonics brand from Costco with the pad attached, and it’s going over 2nd and 3rd floor wood subflooring. The manufacturer instructions explicitly state “Harmonics® flooring with underlayment already attached to the flooring plank requires the use of a moisture barrier (included in the Harmonics Installation kit) over concrete and wooden subfloors. (This is current policy (required over both concrete & wood)”. Therefore, I was planning to follow the instructions and lay the plastic. However, you say plastic sheeting should NOT be put between wood subfloor and the laminate. Your advice seems sound & logical, but I also don’t want to void my warranty – what would you do if you were in my shoes? PS – there is already a layer of 15lb felt between the subfloor (1/2″ plywood) and the underlayment layers (3/4″ particle board) from the original construction in the late 70s.
Brent, while I do not always agree with a laminate manufacturers warranties and installation standards I abide by them. Failure to follow installation standards can and will void a warranty. While Harmonic does require that you use THEIR moisture barrier the Harmonics instructions go on to state, “For concrete subfloors, let the
moisture barrier run up the wall a bit before cutting to size. A molding will be attached to this later.” “For wooden subfloors, cut the moisture barrier 1 inch from the wall.” The purpose of the moisture barrier running up the wall when installed over concrete is to help contain excess moisture below the moisture barrier. The reason for cutting it one inch back from the wall when installed over wood is so that any moisture trapped below the moisture (vapor) barrier has an opportunity to gas off at the sides of the vapor barrier. As far as the 15lb. felt between the subfloor and plywood that is fine and it does not take the place of Harmonics required moisture barrier. Thank you for pointing out that we have not covered Harmonics requirements in our articles for we will now do it so other people will not experience the same confusion.
Terry and Kevin
A quick step retailer has recommended a non Quick step underlayment called Quietwalk with an attached vapor barrier in addition to a moisture barrier for installation of a Quick step Eligna 8mm laminate product even though it is to be installed on a wood subfloor.
Is this Quietwalk’s vapor barrier of the type that is an impermenable vapor barrier of ,7 perm or less that should not be used on installing any Quickstep laminate on a wood subfloor because it will trap condensation and/or cause warranty problems?
Thank you for your very informative website & email posts under all your website issues
Pauline
It is stated that QuietWalk is suitable to go over both wood and concrete. Here are the QuietWalk Specs
Hello
I am on your site trying to find out if I am really at fault. I had my pier & beam home in Texas -carpet ripped up & installed Armstrong laminate tile. It was done in April it is now June 2016 and my floors have warped bad. in every room. It was installed by “professionals”a well known company , They came back out with a moisture tester and said I have a leak somewhere?? That I need tio have my wood flooring replaced then they will come & reinstall???I have found that they were to lay a vabor barrier or someother material before they install the tile which they did not. I am disabled this was a huge expense I am still, paying on . Is this my6 fault I was going to use friends but was afraid of something happening .I am very worried.Your opinion?
Thjank you
JE
Jeanette
Unfortunately I would need to be a mind reader to determine whose fault it is without performing an inspection and testing of your flooring. If the company did not install a required vapor retarder, it was required and the failure to your floor was as a result of not having a vapor retarder, it would be the companies fault. If you have a leak that is damaging the floor and the installation company did not cause the leak it would not be their fault. I would suggest you contact your homeowners insurance agent or insurance claims department and tell them what you were told. If it is a plumbing leak your insurance will often cover all but the deductible. You can also higher a flooring inspector to check it out. Flooring inspectors can be found by going to nwfa.org and clicking on the Find a Professional link or nicfi.or and clicking on Inspector Search, But do speak with your insurance company before you hire an inspector as they may cover the floor.
Good luck, Terry
I am converting my gym in the basement into a bedroom. For the gym I installed 5/8 plywood for flooring over the concrete floor. I now am preparing to install 10mm padded laminate flooring, do I need to install a vapor barrier on the plywood already covering the concrete floor. Or can I just install the padded (allen & roth) laminate over the plywood as is
Hopefully you tested the concrete for moisture before installing the concrete and placed a vapor retarder between the concrete and plywood. While you need to go by the manufacturers recommendations, I would install a vapor retarder over the plywood but not run the vapor retarder up the wall. The vapor retarder directly over concrete should be tuned up the wall and covered by the baseboard.
we installed a floating laminate floor over a hard wood floor about 3 years ago. The hardwood floor was over 10 years old scratched but no moisture problems. Our house is on a concrete slab. Recently we notice a bulge in the floor and removed some of the laminate to discover mold, mildew and moisture damaged hard wood. We removed all the laminate and found a number of spots of moisture and mildew damage on the hard wood. The installer used a sound barrier pad between the hard wood and the floated laminate. Could this have caused a collection of moisture over time resulting in this damage? We never had any problem with moisture until this installation
Pier and beam home with no moisture barrier on the ground. Original sub flooring is 1″ x 6″ boards. I’ve installed 7/16″ OS&B on top of the sub flooring with 15lb felt between the flooring. I’m planning to install Pergo Max laminate in the entire house excluding the bathroom. The question I have is the vapor barrier, should I use one or not?? Pergo states clearly not to use a vapor barrier on wood sub floors. I know I’ve answered my own question, but wanted your advise.
Joe, unless I knew the brand and style of the cushion it would be difficult to know if it was a contributing factor. The moisture content in a concrete slab can change due to a change in direction of slope around your house such as with planting areas or other landscaping. Also water table and other changes. Some floors are not as resistant to moisture as others. My question for you is, Did you conduct the manufacturers required moisture testing of the concrete prior to installing the new floor?
Don
Install a heavy black visqueen vapor retarder on the ground giving it 100% coverage. The 15# felt is provides reduction in sound more than it acts as a vapor retarder. Follow the Pergo installation standards.
When installing EVP (Engineered Vinyl Plank) over concrete, should all of the materials be run in the same direction? For example, moisture barrier is run parallel to longest wall, underlayment on top of the moisture barrier is run in the same direction and then the flooring is run in the same direction?
Also, should expansion joints in the concrete be filled to create a flat surface (concrete is not new) and if so, what material should be used to do so? Lastly, do you recommend caulking the joint where the concrete and the base plate meet along the perimeter of the wall? Okay, last one! The lower walls have a wainscot over the drywall and in some spots along the wall the wainscot nearly touches the concrete while in others there is a large gap (i.e. 1-1.5 inches). This is not an issue in terms of appearance since it will be covered with base moulding, but what would be considered the actual wall when laying the spacers for the first row? Thanks in advance for your help/.
I am in the process of remodeling a rental property after extreme flooding in Louisiana August 2016. The house is approximately 60 years old and built up off the ground, there is no moisture barrier under the house.
There are original wood floors throughout the house with the exception of the bathroom. The floors in the kitchen and bathroom had vinyl laid over the original wood over 20 years ago. We discovered after the flood the floors in the kitchen and bathroom had signs of rot and they have just been replaced with plywood. The floors are in good structural shape throughout the rest of the house but visually “not good”.
I had a man give me a quote for installing laminate over the wood floors, he told me to be sure to purchase moisture barrier padding with the laminate. I started getting prices for laminates and had a salesman at Lowe’s tell me the laminate would not work if I do not have a moisture barrier under the house. He suggested I go with carpet instead of the laminate.
I called the installer and he said he has installed laminate in many older homes like mine throughout this area and has not had a problem with mold, buckling, etc. (he’s been doing this for a while) I’ve been pouring over your site (which is great) and conclude that a moisture barrier should not be used for above ground homes when laying laminate over preexisting wood floors unless recommended by the manufacturer??? Am I correct?
At this point I’m just not sure what to do. I’m thinking the rot may have been caused in the kitchen and bathroom because there was vinyl laid over wood with no moisture barrier under the house….. I have even though it may be safer to lay carpet over wood so I won’t have a problem with mold?
I also looked on some sites about painting the existing wood and new plywood in the kitchen and bath with PPG paint (used to paint wood floors). Any and all advice will be greatly appreciated as I’m feeling a little overwhelmed, thank you
I would not install laminate in the kitchen and bath of a rental property, nor would I put carpet in those areas. For the kitchen and bath either install sheet vinyl or a luxury vinyl floor. You might even consider running a luxury vinyl plank or tile in all rooms.
If the house has a crawlspace, considering installing a heavy black plastic moisture retarder in the area. If the house is raised such as on stilts and you want laminate, I would use a 3 in 1 cushion or other moisture retarder under laminate. Using a retarder between the flooring and a wood substrate is controversial though more and more flooring manufacturers have been recommending it lately.
Carpet is also a good option. Neither the Lowes rep nor installer necessarily gave you bad information.
I would also suggest going to NICFI.org, looking up a flooring inspector in or near your area. Give them a call and ask them a few questions as they will be familiar with the conditions for your locale.
Question:
I have a two story home built on a concrete slab. We installed a laminate floor in the bedroom (2nd floor) over our kitchen / dining room (1st floor). The subfloor of the 2nd floor room is made of wood. I used a 3n1 pad that includes a vapor barrier. I didn’t realize that I shouldn’t do this. I’m worried that I need to pull up the floor and take out the vapor barrier. I’ve talked to two people that tell me that because it is a 2nd floor I shouldn’t worry about it.
Is it ok to leave it as I have constructed it or should I remove the laminate and then remove the vapor barrier and then re install the floor w/o the vapor barrier?
Thank you for your time.
Some of the laminate companies have recently started to recommend vapor retarder on both wood and concrete. While I am not sold on the idea of using it over wood, as long as you didn’t turn the vapor retarder up the wall the 3 in one should be just fine.
Hi. I live in a mobile home. I recently laid laminate flooring throughout the entire place accept my kitchen. The procedure I used: I first laid plywood down over a particle board flooring. Then I laid a foam vapor barrier over the plywood and finally the laminate flooring. Should I be concerned about moisture getting trapped and causing mold? In the kitchen, again I laid down plywood over particle board flooring. Then I laid a plastic vapor barrier and finally I finished the flooring with vinyl click panels. Did I make a mistake in my procedure and do I need to be concerned about mold issues? I also recently had a break in one of my water lines. The vapor barrier under by mobile home filled with water. The insulation got very wet. I went into the crawl space and cut slits in the vapor barrier under the house to release the water. Then I fixed the water line. What are my concerns?
We had a large amount of water enter a crawlspace from a room leak. Room and sub flooring near the leak had the sub flooring and wood floor replaced. However, the crawlsapce adjacent to the room got very humid and aspergillus and pennicillium mold species grew.
The resulting mold in the crawlspace was remediated, HEPA vacuumed, insulation removed, and sealed. (on the under side of the sub flooring)
Some old aspergillus mold spores are in the OSB sub flooring now (based on a recent ERMI mold dna pcr)…..but the buckling in the 1st floor wood floor has gone away. We have 2 commercial grade dehumids in the crawlspace with a humidity sensor. It’s now very dry down there and no live mold for 6 months.
One person in the family is sensitive though to the random toxins that enter from time to time with windy days. A large crawlspace outage fan has helped, but has not solved the mycotoxin type rxn. It’s only a mild illness….not like when the mold first bloomed.
Removing all the sub flooring would be a huge expense due to having to move walls, doors, baseboards, wood flooring, sub flooring, and a stairwell.
Our mold remediator and I are thinking possibly we could remove the wood flooring and leave the OSB sub flooring but seal the toxins out ? To save some expense versus just moving out of the house. Then spray/seal paint the OSB suflooring. Then install an entire new floor, something with less toxin permeability to mVOCs and mycotoxins. Assuming there may be some old mold spores on the underside of the wood floor…that could easily grow back if water damage occurred again or massive humidity.
It sounds like installing a vapor barrier over the OSB sub flooring might encourage moisture from reading hear, .however we have very low humidity in the crawlspace. Dryest crawlsapce 3 mold companies have seen. We also excavated the landscaping to encourage water flow away from the foundation.
Then we were tinkling of ins all a floating type of floor over the vapor barrier.
Any thoughts or guesses on this and if we should just go into the huge expense of removing all the sub flooring and walls ? It seems only 2-3 panels of sub flooring on visual inspection (old mold dark stains) were affected.
We are hoping to come up with some intermediate solution cost wise and instead moving in 2-3 years when kids are away.
Bombproof Vapor barrier over subfloor ?
Vinyl or wood over the vapor barrier ?
Sorry for the long post.
Thanks for all the great comments on here
Seymour
In reply to your questions:
1. I live in a mobile home. I recently laid laminate flooring throughout the entire place accept my kitchen. The procedure I used: I first laid plywood down over a particle board flooring. Then I laid a foam vapor barrier over the plywood and finally the laminate flooring. Should I be concerned about moisture getting trapped and causing mold? Answer: If the moisture of the particleboard or plywood was excessive at the time of installation, it is possible. This excessive moisture would usually be followed by expansion or cupping of the flooring shortly after installation. Otherwise you are most likely okay. This does not eliminate possible moisture from maintenance such as wet mopping.
2. In the kitchen, again I laid down plywood over particle board flooring. Then I laid a plastic vapor barrier and finally I finished the flooring with vinyl click panels. Did I make a mistake in my procedure and do I need to be concerned about mold issues? Answer: If the moisture level of the plywood or particleboard was far too high at time of installation it will usually start to swell fairly fast. If you do not see any swelling, you are likely okay.
3. I also recently had a break in one of my water lines. The vapor barrier under by mobile home filled with water. The insulation got very wet. I went into the crawl space and cut slits in the vapor barrier under the house to release the water. Then I fixed the water line. What are my concerns? Answer: This is a bigger problem. You need to make sure that the insulation thoroughly dries out as excessive moisture below could cause problems not associated with the installation.
If you are overly concerned about potential problems brought on from your installation, put yourself at ease. Go to NICFI.org and hire a flooring inspector in your locale. The inspector can check things out and tell you if you have a problem.
Sorry,
Can’t be much help here. You are dealing with mold and mold is a huge health risk. You need the mold experts on site to assist you in any decisions you make with is remediation.
Wouldn’t using a vapour barrier on concrete like 6m poly lead to mold? IF you get water it wouldn’t evaporate.
I taped down some poly on my concrete floor (34 year old home) for 2 days and got no issues.
Im thinking of laying my laminate with foam underlay right on the concrete without a vapour barrier.
Thoughts?
Vic
I would be more concerned with not using a vapor barrier (retarder) resulting in mold as it feeds on the laminate floor. Before deciding not to use a vapor retarder, make sure the manufacturer of the laminate product you are using, allows for it. If they require a barrier or retarder and one is not there, you will likely have no warranty coverage. My best advice is to either follow the installation requirements or choose a product that does not require a separate vapor barrier if you insist on going that way.
We recently have had parts of our wood flooring fail twice. The first time it seemed the glue was just not holding and the floor buckled a little in one spot. We had a company come out and replace a few boards and glue them down again. Recently another are began to buckle. We carefully removed a few boards only to realize their was mold on the back of the boards! We then began removing larger sections and found that a large portion of our glue down engineered wood floor has somehow gotten moisture under it and mold has formed on much of it. We had American Leak Detection come out and test for a water leak but their technician said he can not find a leak. His surface test equipment showed some areas much more saturated than others, I believe the highest was a 22 and other areas were 5-6. This is a newer home, built in 2002 on a slab and all water lines are PVC type and run in the attic. We have good draining around the home and all downspouts have drain lines to the street. Outside areas were inspected but they did not find a problem with the draining. We’ve also pulled up the carpet and can see a large area of discoloration (darker) in sections of the concrete and a white powdery substance that is like calcium that has come up through the concrete. We want to repair or replace the floor but I don’t want the problem to repeat. I don’t know what to do or who to call to get help. I have no idea where the water is coming from or why it would be seeping up through the concrete. We live in Clovis, CA which is a fairly dry area. I would appreciate any advice you could provide.
What is the purpose of the moisture barrier?
14 years ago I, in my ignorance, installed Pergo, with backing, in my basement on a concrete floor. I did not install a moisture barrier. The floor has held up beautiful; no buckling, gaps or peaks.
Am I just lucky?
Yes Stephen, you are lucky!
Really excellent and informative website. Thank you in advance. I am about to put down a laminate floor over concrete slab. The laminate has a maximum allowable moisture of 5lbs/1000ft/24hrs. Calcium Chloride test readings show a couple areas where moisture is 4.9lbs and 5.3 lbs. I was going to use the 6 mil poly moisture barrier method where the subfloor is completely covered and the poly sheeting bend up the walls a couple inches, and ends up hidden behind the baseboards. On top of this 6 mil poly, I will also be putting a high-quality underlayment which has moisture barrier included. QUESTION: Will this “up the wall” poly method cause the subflloor’s moisture emissions to flow toward the perimeter of the room and create mold between the walls?
I am hoping someone can offer advice. Let me know if I am wrong. I am pretty cautious about putting down a new pergo floor because I have spent a lot of money. But I am in florida and I want to make sure I create a bulletproof solution. Here is my plan:
1) For areas on my concrete floor that I have levelled to a feathered edge, I notice they can produce a powder when walked on. I guess because they are so delicate and footsteps are grinding on them. Therefore, it is my plan to coat these areas with “Drylock Floor & Wall” to sort of hold them together, and so I don’t end up with powdery dirt under my underlayment.
2) Over the top of my concrete, I am going to install 6 mil polyethylene film followed by recommended underlayment.
QUESTION: If moisture ever comes up through my slab, will it end up pooling under the moisture barrier? Or will it eventually find it’s way back down into the concrete sub floor? I am worried that my moisture & ddrylock “crumble-prevention” method will trap TOO MUCH water without an escape route.
Thank you for any helpful advice you can provide.
I am installing Mohawk Revwood laminate flooring throughout most of my house which was built in 2015. The house has a day light basement with a concrete floor. Mohawk requires that I lay a vapor barrier under the laminate. I bought moisture barrier. Is this the same as a vapor barrier? Should I leave a space along the walls when installing the moisture barrier? Also you have recommended not laying down a moisture barrier when installing laminate over a wood subfloor which I have on main floor. Mohawk says that I may or may not do this. Which advice is right (I plan on laying the laminate in my kitchen)?
Looking for insight. Looked a home today, and there were discoloration around the perimeter of the hardwoods throughout the home. There was no visible sign of water intrusion along the slab (no deterioration of the flooring and it’s finish – and no visible or physical damage of the quarter round or molding around entire floor).
Asked selling agent about the issue, and they stated that the vapor barrier under the flooring (glued to the slab) has caused discoloration over the years. Home is just over 15 y.o.. I have never heard of this – is this possible?