Shrinking floating floor has been a common floating floor concerns in recent years. Seen often with strand bamboo flooring, also laminate, engineered wood and even luxury vinyl floating floors. A floor looks beautiful for a while and suddenly develops wide gaps at plank ends, sides along walls or at doorways.

The Panicked homeowner calls the dealer and says, “I have a shrinking floating floor!” After a quick visit to the house, the dealer, installer and perhaps the distributor agree that the floor is shrinking. Now the blame game starts.

• The homeowner blames the dealer for selling them a lousy product.
• The dealer blames the installer for not installing the floor correctly.
• The installer blames the manufacturer for selling a defective product.
• The manufacturer blames the homeowner for not properly caring for their new floor.

The Weinheimer Group or other Certified Inspector, will visit the installation. To end this blame game they will perform testing, identify cause and document cause in a written report.

Cause and Effect Shrinking Floating Floor

There are normal and abnormal causes of shrinking floating floor. In this article we discuss those reasons and will further expand upon the cause. The article will not make you a shrinking floor expert. It is our intention to give you a better understanding of why you are seeing gaps. You may also see peaks, a concern expanded on in our article Growing Floating Floor.

Shrinking floating floor and wide gaps are issues that most often occur from loss of moisture. The flooring was installed when the moisture content was too high. Or, installed at the proper moisture content and dried to a lower content. In most areas of the country flooring is installed at about 8% moisture content. Higher, drier climates the number may be 6%. More humid coastal and southeast areas, the floor might be installed at 9-10%. Competent flooring installers, familiar with the locale will know the historical norms.

Normal Moisture Content (MC) Fluctuations

Wood, bamboo, laminate is hygroscopic, which means its MC will fluctuate with changes in the relative humidity (RH) of the surrounding air.

• As relative humidity increases, the MC increases, and the floating floor expands.
• During dry periods, MC decreases, the wood shrinks, narrow gaps open. If the gaps go back together during more humid periods, you have a normal condition.
• Wide plank flooring will experience wider gaps during dry periods. With wide plank flooring, narrow gaps may remain during more humid periods. These narrow gaps may be considered normal in locales with regularly low relative humidity, humidity fluctuates more than 15% throughout the year and you do not control the relative humidity.

Less Shrinking Occurs When

• Flooring attaches to the substrate with glue or nails. (Floating floors are not and cannot be attached)
• You live in year-around stable relative humidity conditions.
• You have a built-in humidity control system that properly maintains your relative humidity.

Gapping associated with noise, usually occurs when the moisture content of the flooring has reduced from a higher summertime MC to a lower winter (heating season) content. Solid click style floating bamboo is the most common floor to experience shrinkage problems. 

Abnormal Reasons for Shrinking Floating Floor

Inadequate Acclimation

Inadequate acclimation is the failure to adapt flooring to its installation environment. Acclimation time requirements will differ by locale, climate and the amount of moisture in the flooring product when received. My company, The Weinheimer Group, has offices in Washington and Oregon. In these states, we have coastal and lake areas with high average relative humidity. We also have high desert areas with low average relative humidity. Acclimation in Arizona is different than in the southeast United States. To achieve equilibrium moisture content, the installer may need to bring moisture up or down. The North American Laminate Association (NALFA) states, “Just as other materials in the home expand and contract, laminate floors react to the changes in temperature and humidity. To allow the planks to adjust to the environment where they will live, acclimation is necessary and important”.

Acclimating flooring by time alone, often means problems. Installation instructions may state a required acclimation time. The time’s a guideline and not set in stone. Some floating floors may be at equilibrium moisture content when received. Others may require a few weeks of acclimation, before the moisture content is acceptable for installation.

Keep in mind when acclimating strand woven bamboo, that extreme variations in density and fibers sheathed in glue will often result in the flooring at the job site taking a long time to acclimate. For best prevention of gaps in strand woven bamboo, think of acclimation time in weeks and not days.

A flooring installers best line of defense against floating floor gaps is to use a reliable moisture meter and a hygrometer to verify that both the product and structure is ready for installation.

Two Types of Moisture Meters – Pin and Pinless

Pin and pinless meters, both measure moisture content. There are two significantly different technologies to these two types of meters.

Pin Style Resistance Technology
Pin-style meters use electrical resistance. The probes, or “pins” are inserted into the wood, a small electrical current is passed between the two points, and the amount of resistance is correlated into a moisture content reading.

Pinless Electromagnetic Wave Technology
Pinless meters, often referred to as non-destructive meters use electromagnetic wave technology instead of pins. The meter sends out electrical waves at a frequency that creates an electromagnetic field in the area under the sensor pad. The moisture content is correlated to the signal it reads back.

Keep the following in mind regarding moisture meters.

• Accurate moisture readings of bamboo flooring especially strandwoven, also strandwoven eucalyptus are more difficult to obtain than with other wood or laminate floors.  Bamboo does not have a density. Strandwoven product have binders in them that make the accuracy of moisture readings more difficult.
• Not all moisture meters are equal, the accuracy of cheaper meters, varies as much as 25%. The better-quality meters such as those by Wagner, Lignomat, Protimeter Tramex and Delmhurst will generally be accurate within 5%.
• The better meters will have settings for different wood groups including strandwoven products.  A good pinless meter can take readings at a depth of 1/4″ to 3/4″.
• Pin meters work well on traditional bamboo when inserted in the direction of grain.
• Pinless meters work better then pin with strandwoven bamboo.
• Some flooring manufacturers prefer that all readings be taken with a pin style meter.
• Pin style meters will leave small holes in the wood and your only choice may be to use a non-destructive meter.

Substrate Flatness

When a substrate has high or low areas expect deflection and squeaks. With movement and other stresses placed on the flooring gaps will appear. Floating floor shrinkage (contraction) is taking place and because of low areas and/or other stress the click locking system has pulled apart and wide gaps have appeared.

The industry standards specify that the surface of the subfloor must be flat to within 3/16″ in a 10-ft. radius. Many manufacturers installation guidelines state 3/16″ in 10 feet or 1/8″ in 6 feet. To prevent problems, fill low spots in the subfloor and grind down high spots.

Expansion Space

• Flooring expands and contracts with changes in temperature and relative humidity. As it expands, the expansion space becomes smaller. As the flooring contracts the expansion space becomes larger. If the flooring is unable to move as units, the floating floor gaps, rises or both.
• Expansion space is not an option, it is a requirement. Install floating floor with sufficient expansion space or expect problems. Expansion space must be left around walls, cabinets, thresholds, fireplaces and all other vertical objects. A single plank without expansion can cause floating floor gaps and buckling.
• Installing a single plank without an expansion gap can cause flooring to pull apart, peaks, buckles and squeaks.
• In absence of clear-cut installation guidelines, expansion space at a minimum should be the thickness of the material being installed. If the area of installation is over 30’ in a single direction, add another 1/16” for every 10 feet of installation.

No Expansion Space in Doorways

• For best performance, most floating floor requires that an expansion gap be placed in the passageways between rooms and non-symmetrical areas. A transition strip such as T-molding is placed over the expansion space.
• When an installation flows through doorways you may end up with what appears to be a shrinking floating floor. With normal expansion and contraction, the floating floor is not able to move as a single unit. Suddenly, random wide gaps are appearing and you see the appearance of a shrinking floating floor.

Improperly Installed Transitions

• Trim glued to the surface of the floating floor to cover the expansion space is a no-no. The glued trim hits the wall, threshold, fireplace or other vertical object preventing expansion. With blocked expansion, the click joints may come apart, squeak or buckle.
• Transition strips glued to the substrate using too much construction adhesive to attach the strip, the glue can ooze and lock the floor in place. It is best to use the track that comes with T-molding. If glue is a must, use silicone as it will remain flexible.

Improper Stagger

• Combined with a substrate that is not flat, end and side joints that have not been properly staggered can disengage. Staggering  the planks for structural integrity. The required stagger can be found in the manufacturers instruction guide for the product you are installing.

Improper Baseboard Installation

A flooring installer has just completed the installation and up to this point has done everything by the book. The carpenter or homeowner install beautiful new baseboards, stand back and admire the job. A few months later wide gaps or peaking are appearing in the floating floor. The dealer or installer get that all too familiar call, “I have a shrinking floating floor.” or “My floor is growing.”

• Baseboard Width
• The baseboard must be wide enough to cover the required expansion gap and still cover enough of the remaining floor so gaps will not occur around the edge as the flooring is experiencing normal contraction. If the required expansion space is ½”, half inch-wide baseboard will not cover the expansion gap and at least a ¼” of the floating floor. Do not force the installer to leave too little expansion space. Leave proper expansion space and cover it with a wider baseboard or quarter round.
• Pinching Base
• Baseboard  pushed too tight will pinch a floating floor, causing gaps in one or more areas. Always leave a narrow gap (at least the thickness of a business card) between the flooring and the bottom of the baseboard. You may not like seeing the gap, but you will like it more than your floating floor pulling apart.
• Baseboard and Quarter Round Fasteners
• Properly place nails and staples used to install baseboard trim. Angle fasteners so they do not enter the expansion zone or go through the floating floor. Even a single plank locked in by a staple, nail, screw or other fastener, can and will prevent normal expansion and contraction.

Adjustable legs on dishwasher

• Unlike movable refrigerators, washers and driers, dishwasher are built-in appliances. When cranking down the adjustable legs of a dishwasher they pinch the floating floor, preventing free movement. A wide gap often develops in front of the dishwasher. This is not a shrinking floating floor. To prevent this, either stop the flooring in front of the legs, or drill holes through the floating floor and adjust legs against the substrate and not the flooring.

Cabinets

• Installing cabinets or an island on top of the floating floor prevents uniform expansion and contraction. Install the cabinets first and then install the floating floor around them.

Interior Environment

• Failure to control the relative humidity in your home may result in a shrinking floating floor and/or other problems. Most flooring performs best in a relative humidity between 30 and 50 percent, and temperature between 60 and 80 degrees. Always check the installation and maintenance documents for the product installed. Consider the installation of a humidification system when installation is taking place in a locale with excessively high or low relative humidity or big swings in humidity.

Manufacturing

Wet hardwood and bamboo

When bamboo and wood flooring is manufactured, there is a period where the flooring is dried and the moisture becomes balanced, prior to milling. When this period is rushed and the flooring has not been properly dried the product is shipped with too high of a moisture content. This wet flooring will start to shrink, especially when delivered to a region where the relative humidity is low. If this higher moisture content flooring is installed during periods of high relative humidity the shrinkage may not take place until the winter when the thermostat is turned up and relative humidity becomes lower.

Drying bamboo at the factory is tricky as it is difficult to measure moisture content and unlike wood, most factories do not dry the bamboo down to a target moisture content and instead rely on a predetermined schedule. Moisture content of individual strips can be misleading due to the density variation. Moisture content is a problem for all manufacturers of strand bamboo. Wood and laminate the moisture content is much easier controlled and measurable.

Steps in Preventing Shrinking

Floating floor as with other products expands (grows) and contracts (shrinks). Expansion and contraction is a characteristic and not a defect. It must be considered and allowed for prior to, during and after the installation.

• Select a quality floor.
• Read and follow the installation instructions.
• Acclimate properly.
• Properly prepare the substrate.
• Leave sufficient expansion space around walls, cabinets, sliding doors, fireplaces and other vertical objects for periods of expansion.
• Do not lock in the floating floor by baseboard pinching or fasteners.
• Control your relative humidity prior to, during and after installation.
• Properly maintain your flooring per the manufacturers guidelines.

Follow these commonsense rules and you will have a beautiful floating floor that last you a long time.