By Brett Miller, NWFA Vice President Technical Standards, Training & Certification
One of the telltale ways to differentiate real wood floors from lookalike products is how they sound when walked upon. Real wood floors have a distinctive sound in response to foot traffic, while imitation wood floors tend to produce a plastic or hollow sound.
There are times, however, when wood floors produce sounds that may not be considered normal. The key to determining this is to first identify the cause of the sound, then evaluate whether the noise is considered normal within industry standards—and if not, resolve how to fix it.
Squeaking, Popping and/or Crunching Sounds
Identification
Squeaking, popping, or crunching sounds are audible noises that are produced either within the wood floor itself or from within the flooring system.
Causes
Squeaking, popping, and crunching sounds can have a variety of causes:
- Old age of the floor and/or structure.
- Wood flooring installed while not in equilibrium with the end-use environment.
- Incorrectly milled flooring that has loose tongue and groove engagement.
For wood subflooring systems:
- Loss of fastener holding power resulting from a reduction in moisture within the wood subflooring system.
- Improper subflooring material that will not hold fasteners adequately.
- Weak subfloor or subfloor system.
- Foundation or support pillar settlement.
- Water-damaged subflooring, as follows:
- Plywood can swell, distort, and delaminate when exposed to high moisture levels, impacting fastener holding power.
- OSB can swell when exposed to water, decreasing density and reducing within-board strength, which impacts fastener holding power.
- Improper spacing between abutting wood subfloor panels.
- Improper or missing adhesive between the wood subfloor panel and joist systems.
- Improperly driven nails or screws in wood subfloor panels.
- Noisy or missing tongue and groove in subflooring material.
- Improper joist spacing/panel thickness combination.
- Deformed or fractured joists.
- Ductwork rubbing against the underside of the wood subfloor.
- Delamination of plywood material.
- Screed/sleeper systems out of flatness tolerances.
For nail-down wood floors:
- Flooring not installed tightly together.
- Voids between the wood floor and the subfloor.
- The flooring underside being blown-out from the fastener, forcing the flooring off the subfloor.
- Debris between boards or subfloor during installation.
- Wood floors installed parallel to the floor joists over inadequate substrates.
- Deflection in subflooring.
- Improper fastener schedule.
- Improper fastener (wrong length, gauge or type).
- Overdriven or underdriven fasteners, resulting from incorrect air compressor pressure settings.
- Cracked tongues.
- Substrate not flat to within required tolerance (3/16” in 6’, or 1/4” in 10’).
- Improper underlayment material used under the wood floor.
- Lack of expansion around vertical obstructions.
- Metal floor trusses coming into direct contact with fasteners.
For glue-down wood floors:
- Flooring not installed tightly together.
- Voids between the wood floor and the subfloor.
- Debris between the flooring and the subfloor during installation.
- Early foot traffic before adhesive dries.
- Deflection in subflooring.
- Concrete substrate moisture.
- Incorrect adhesive and/or moisture mitigation system.
- Inadequate bond between the subfloor and the adhesive, due to poor preparation or incompatibility.
- Improper adhesive use:
- Wrong trowel or spread rate.
- Inadequate adhesive transfer.
- Improper flash time.
- Not using a roller when recommended.
- Substrate not flat to within required tolerance (1/8” in 6’, or 3/16” in 10’).
- Lack of expansion around vertical obstructions.
- Improperly mixed lightweight gypsum concrete or patching compound.
For floating wood floors:
- Debris between the flooring and the subfloor during installation.
- Deflection in subflooring.
- Improper underlayment material used under the wood floor.
- Improper glue used, or improper glue application.
- Failed or broken glue bond.
- Broken, missing or disengaged locking mechanism.
- Lack of expansion around vertical obstructions.
- Pinch-points in the installation.
- Bowing of flooring outside of manufacturer’s tolerances.
- Substrate not flat to within required tolerance (1/8” in 6’, or 3/16” in 10’).
- Flooring installed that wasn’t approved for floating installation method.
- Subfloor moisture.
Cures
Note that the structural integrity of the subfloor system is not the wood flooring contractor’s responsibility unless he/she installed the subfloor system. Structural issues should be addressed by a qualified professional. If it is determined that the noise is the result of improperly installed or failing subfloor systems, removing the wood floor may be necessary to make repairs.
Moisture-related issues must be identified and addressed prior to correcting any noise-related issues. Lubricating materials such as talcum powder or WD-40 sometimes are used to minimize board-to-board noises temporarily, but are not considered permanent fixes. Repairs for improperly milled flooring should be addressed as suggested by the flooring manufacturer.
Individual board replacement or injected adhesives are commonly acceptable repairs. If access below the floor is possible, screws, adhesives, wedges or shims can be used to strengthen the subfloor system.
If there is inadequate perimeter expansion, it may be possible to cut in expansion into an existing floor.
Hollow Sounds
Identification
Hollow sounds are audible noises that are produced within the installed wood floor itself.
Causes
Hollow sounds can have a variety of causes, as follows:
For nail-down wood floors:
- A flooring void (wormholes, shake, bark pockets, engineered flooring core voids, etc.).
- Slight imperfections or voids in the subfloor.
For glue-down wood floors:
- A flooring void (wormholes, shake, bark pockets, engineered flooring core voids, etc.).
- Slight imperfections or voids in the subfloor.
- Concrete subfloor flatness not within required tolerance (1/8” in 6’, or 3/16” in 10’).
- Small area voids in the adhesive or voids within the properly applied adhesive.
- Inadequate bond between the subfloor and the adhesive (poor preparation or incompatibility).
- Improper adhesive use.
For floating wood floors:
- Hollow sounds and slight vertical movement are considered normal when properly installed.
Cures
When a void between the flooring and substrate is tied directly to vertical deflection within the installed flooring system, issues with flooring performance may become a factor and should be assessed on an individual basis. Possible cures could include adhesive injections or individual board replacement.
The National Wood Flooring Association has detailed information about wood flooring noises and corrections available through NWFA University, an online training platform that is convenient and affordable. More information is available at nwfa.org/nwfa-university.aspx.
