Shrinking floating floor concerns are common. This appearance can be seen with strand bamboo flooring, laminate floors, engineered wood, and even luxury vinyl floating floors. A floor looks beautiful for a while. Suddenly, wide gaps develop. The gaps are at the ends or sides of planks, perhaps at walls or 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.
Who’s Fault Is It?
Everyone is blaming the other, so whose fault is it? It’s time to call in an independent third-party inspector. A Certified Floor Inspector, such as TW Group, will visit the installation. The inspector will thoroughly examine the installation and installed product, perform testing, gather installation and claim history, review technical data, and identify the cause. The findings and conclusions will be documented in a written report.
Cause and Effect Shrinking Floating Floor
There are normal and abnormal causes of a 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. We intend 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 United States, flooring is installed at about 8% moisture content. In higher, drier climates, the number may be 6%. In 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, and laminate are hygroscopic, which means their 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, and 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, where 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-round 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.
Importance of Acclimation
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 TW Group Inspections, aka The Weinheimer Group, serves 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 from 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”.
Acclimation Time
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. During acclimation, you will regularly need to check the flooring with a moisture meter.
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 the 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.
Moisture Meters – Pin and Pinless
Before, during, and after installation, the flooring installer will need a moisture meter. The two major types are pin and pinless meters, which both measure moisture content. There are two significantly different technologies for 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 products 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 the grain.
- Pinless meters work better than pins 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.
Other Shrinkage Causes
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.
- What appears as shrinkage (contraction) is taking place. This is 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 a unit, the floating floor gaps, rises, or both.
- Expansion space is not an option; it is a requirement. Install a 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. It can also cause flooring to pull apart, cause peaks, buckles, and squeaks.
Tip: In the 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.
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 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; the glue can ooze and lock the floor in place.
Tip: It is best to use the track that comes with the T-molding. If glue is a must, use silicone as it will remain flexible.
Installation Concerns
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 installs beautiful new baseboards, steps back, and admires the job. A few months later, wide gaps or peaking are appearing in the floating floor. The dealer or installer gets that all too familiar call, “I have a shrinking floating floor,” or “My floor is growing.” But is it?
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 floor experiences normal contraction.
- If the required expansion space is ½”, a half-inch-wide baseboard will not cover the expansion gap and at least a quarter inch 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 trim.
Pinching Base
- A baseboard pushed too tightly will often 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 dryers, dishwashers 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 the 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 Concerns
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, before milling. When this period is rushed and the flooring has not been properly dried, the product is shipped with too high a moisture content. This wet flooring will start to shrink, especially when delivered to a region where the relative humidity is low.
When flooring is installed with a high moisture content during periods of high relative humidity, shrinkage may not take place until the heating season. The thermostat is turned up, and the relative humidity becomes lower. As the relative humidity lowers, the floor starts to dry and contract. ,
Drying bamboo at the factory is tricky, as it is difficult to measure moisture content. Unlike wood, most factories do not dry the bamboo down to a target moisture content; instead, they 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. With wood and laminate, the moisture content is much easier to control and measure.
Additional Tips For Shrinkage Prevention
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 lasts you a long time.
Need Help? Get an Expert Laminate Flooring Inspection
Avoid costly mistakes in choosing and installing laminate flooring. If your flooring has experienced failure, TW Group Flooring Inspection can help with inspections and consultations. Contact 800.621.3427 or submit an online inspection request.
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