Moisture: The Primary Cause of Floating Floor Growth
Increased moisture is the cause of a growing floating floor. The effect will range from no noticeable change in appearance to peaking, cupping, buckling (tenting), warping, delamination, blistered edges, finish damage, squeaking, and gaps.
Moisture Loss and Gain
Engineered wood, laminate, and bamboo flooring are hygroscopic. These materials increase and decrease in moisture content with a change in the ambient relative humidity (RH). To better understand hygroscopicity, think of the kitchen sponge. The wet sponge absorbs moisture and swells. As it dries, it shrinks. That’s what wood and bamboo products are constantly doing, though usually in a subtler way.
When exposed to elevated moisture levels, a floating laminate floor may expand beyond its designed limits, leading to visible and structural damage. Also see Shrinking Floating Floor
Water-Resistant ≠ Waterproof
The surface layer of laminate flooring is melamine. Most floating floors have protective finishes and coatings such as aluminum oxide and polyurethane. The finish retards surface moisture damage and moisture while not totally preventing it.
The exposed face of wood, laminate, and bamboo floors is water-resistant, not waterproof. Water-resistant flooring resists the penetration of water to some degree but not entirely. Luxury vinyl plank and most resilient style flooring products are much closer to waterproof (impervious to water).
Hidden Moisture
Often, water is not seen on the surface of the floor. It may be flowing below the growing floating floor. A leaking dishwasher, washing machine, toilet bowl, or even a slow pipe leak can result in a significant amount of water loss. The moisture may be in the form of water vapor from a crawlspace or concrete slab. Any cracks or damage in the concrete slab must be addressed.
Visible Moisture
Moisture is sometimes visible in a form other than surface water. Moisture might be tracked onto the floor from rain or snow. Too much moisture during maintenance, accidental spills, or a peeing pet. This moisture is absorbed at the flooring joints when not wiped up quickly enough. With some of the less expensive floating floors, quick enough might mean immediately. With a better quality floating floor, you may have as little as a few minutes or as much as an hour.
Clues to Moisture
Blistering
Excessive moisture during cleaning, spills, or even a urinating or vomiting pet may show as blisters along the edge of planks. Blisters crossing between joined plank edges are easily identified as moisture-related. The cause of those that affect a single edge can be more difficult to identify. These blisters are considered site-related damage in the absence of a warranty that protects the end-user from such damage.
- Cause: Excessive surface moisture, spills, or pet accidents
- Effect: Raised edges or bubbles between planks
- Note: Blisters crossing plank joints are moisture-related; single-edge blisters may require deeper inspection.
Buckling (Tenting)
The growing floating floor expands and lifts off the subfloor. Caused by excessive moisture from above or below the growing floating floor. A pipe breaks, a leaking appliance, or a wet slab from below. High relative humidity or too much moisture on the floor from above. It can also occur due to the Greenhouse Effect in a closed-up house without an operating or inadequate HVAC system. Improper acclimation and installation techniques can aggravate buckling.
- Aggravating Factors: Inadequate expansion gaps, poor acclimation, HVAC failure, or continuous flooring across rooms
- Cause: Severe expansion due to moisture from above or below
- Effect: Planks lift off the subfloor
Cupping
Cupping occurs across the width of the individual pieces of flooring. The edges are high and the center is lower. It generally develops gradually. Cupping results from a moisture differential within the boards. Usually, high moisture on the bottom side of the floating floor planks from plumbing or appliance leaks or vapor emissions from the slab, subfloor, or crawlspace. Improper acclimation may result in subtler cupping. Dry cupping occurs with engineered flooring because of low humidity levels and is often associated with checking (cracks) in the face of the board.
- Cause: Moisture imbalance—typically higher on the underside
- Effect: Edges curl upward, center dips
- Types:
- Wet cupping: From leaks or vapor emissions
- Dry cupping: From low humidity, often with face-checking
Delamination
Seen as the separation of the floating floor layers. Delamination may be a manufacturing concern because of poor bonding issues. Also, caused by flooding, excessively wet maintenance, or other excessive job site moisture, including extreme fluctuations in the ambient relative humidity. Note: May be site-related or a bonding issue
- Cause: Flooding, wet maintenance, or manufacturing defects
- Effect: Layers of laminate separate
End-Lifting
The ends of the floating floor have a raised appearance. More common causes include too much moisture during or following installation. End lifting can also be a maintenance or manufacturing related condition.
- Cause: Moisture during or after installation
- Effect: Raised plank ends
- Note: Can also stem from manufacturing inconsistencies
Finish Damage
Moisture-related finish damage on the edges of an engineered wood flooring occurs much like the blisters on the edge of a laminate floor. Excessive moisture enters at the edge of the boards and finds its way under the finish, resulting in a peeling finish. Even more severe damage is seen when the moisture level of the hardwood increases to the point that the finish on the face of the plank is now peeling. A competent flooring inspector should be able to determine if this is a finish bonding issue, moisture-related issue or both.
- Cause: Moisture intrusion at plank edges
- Effect: Peeling or bubbling finish
Inspection Tip: A qualified inspector can determine if the issue is moisture-related or a bonding failure
Face-Checking
Lengthwise cracks in the veneer of an engineered wood floor. Typically occurring with flooring manufactured at an MC incompatible with the local environment. Face checking can occur from humidity levels not properly controlled. The relative humidity fluctuates significantly between high and low.
- Cause: Incompatible moisture content (MC) or RH fluctuations
- Effect: Lengthwise cracks in veneer
- Common in: Engineered wood and bamboo flooring
Gaps
Abnormal gaps, sometimes seen with edge crush (Compression set). This occurs when a growing floating floor expands from being exposed to extreme moisture. With a floating floor gaps, can also develop as part of the flooring expands into areas without sufficient expansion space and adjacent flooring pulls in different directions resulting in gaps. There are many other causes for gaps, associated with the shrinking floating floor.
- Cause: Expansion into restricted areas or compression set
- Effect: Visible spacing between planks
- Note: Gaps may also result from shrinkage—see related article: Shrinking Floating Floor
Greenhouse Effect
The flooring shrinks and swells because of limited air movement and inconsistent humidity levels. A building closed for an extended period with little to no air control or air exchange. Elevated heat, such as sunlight through windows, creates condensation and abnormal humidity levels. During this time, shrinkage or expansion occurs as the flooring attempts to stabilize with the atmosphere.
- Solution: Maintain consistent HVAC operation and airflow
- Cause: Closed buildings with poor air exchange
- Effect: Condensation, abnormal RH, and flooring instability
Squeaking and Popping
As a floating floor expands from excessive moisture, it will often lift enough off the subfloor so that it deflects and squeaks. Flooring locked in at walls or other fixed objects will exacerbate squeaking. Extremely heavy furniture, such as a heavy pool table setting on it or cabinets built on top of the floating floor, results in surrounding expansion. A damaged locking joint or improper milling of the locking system will also result in squeaking and popping. Performing an investigation of the concern should identify the cause.
- Aggravating Factors: Heavy furniture, cabinets on top of flooring, or improper installation
- Cause: Expansion lifts flooring off subfloor, or locking system failure
- Effect: Audible noise during foot traffic
Tips For Preventing a Growing Floating Floor
Prevention of the growing floating floor is a combined effort. Proper product selection, installation environment, the installation and maintenance are all factors in how the flooring of choice will perform.EXPANSION GInadequate or improper expansion is a major contributor to the growing floating floor. It is iant to allow for expansion gaps that are wide enough to allow for the growth of the floor. At a minimum, place expansion gaps in the proper locations and as wide as the installation instructions call for.
On the rare occasion that the manufacturer does not provide instructions, a good rule of thumb, add a gap at least the thickness of the product being installed. In larger rooms, add additional expansion space. Remember that the wider the room, the more the growth.
Heavy Objects
The weight of heavy furniture such as pool table over 500 lbs. and grand pianos. Even distributed over multiple legs, they may pinch a floating floor against the substrate or cause joint damage. When pinching occurs, the floor is unable to move as a unit. As the flooring expands, it lifts off the substrate. Deflection is seen, squeaking is heard. The floor may even buckle if the moisture level increases enough. Proper stagger helps to reduce weight caused joined damage. To help distribute the weight and prevent joint damage, use a wide foot, rubber coaster.
Objects Installed On Top of Floating Floor
Wood and pellet burning stoves, kitchen islands, and cabinets installed over a floating floor are an even greater issue. When remodeling or new construction, avoid laminate under the cabinets. These items locked the floating floor in. When the floor is unable to float, it expands, and you have the problems associated with the growing floating floor.
Molding and Trim
Pinched Molding
Molding and quarter round that pinches a floating floor can result in problems such as squeaks and buckling. Pinching occurs from nails that go through the floor or into the expansion space. Fasteners need to go in the wall or cabinet, and not the floor. The floating floor is also pinched when the molding is pressed to tightly against the floating floor.
Hint: Always leave a space between the bottom of the molding or quarter round at least the thickness of a business card.
T-Molding
This trim covers the expansion space that is left in non-symmetrical areas and doorways. The expansion gap separates the rooms so that each can float freely while expanding and contracting. Failing to leave this expansion gap often results in concerns such as buckling, squeaking, and gaps.
Environment
Relative Humidity (RH) & Temperature
Floating floor installed in a locale with large swings in relative humidity. If the relative humidity is routinely low or routinely high, consider installing a built-in humidification system. Remember, most floating floors perform best at a temperature that ranges between 60-80 degrees Fahrenheit and a relative humidity range of 35-55 percent. Always follow the written guidelines for the product you have installed.
Maintenance
Maintain your floor by following the manufacturer’s maintenance guidelines. The well-meaning salesperson or friend may have given you good information. On the other hand, the information they shared or you found on the internet may end up damaging your beautiful new floor.
A Few Prevention Tips
- Acclimate flooring properly before installation
- Leave adequate expansion space around all fixed objects
- Use moisture barriers over concrete slabs or crawlspaces
- Maintain consistent indoor humidity (ideally 35–55% RH)
- Clean spills immediately—don’t rely on water resistance alone
- Avoid wet mopping; use damp or dry methods only
Final Thoughts
A growing laminate floating floor is almost always a moisture story. Whether it’s a subtle cupping or dramatic buckling, understanding the cause helps prevent costly damage and ensures your flooring performs as intended. When in doubt, consult a certified flooring inspector to determine whether the issue is site-related, installation-related, or a product defect.
The growing floating floor and the shrinking floating floor are closely related by moisture content (MC). The growing floor is expanding, and the shrinking floor is contracting with a change in moisture content. As discussed, there is one major cause but many effects.
Expert, certified flooring inspectors such as Kevin Weinheimer investigate problem floors, perform onsite testing, and make an in-depth search for the cause. The condition may be site or maintenance-related. Other times, the product or installation is related. Sometimes a variety of concerns. The inspector will document concerns and furnish a fully written report to the commissioning party.
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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