Common Wood Floor Failures

By Frederick M. Hueston

Natural wood floors add special warmth to a space and can increase the value of a home or business. However, with that said, wood floors are not flawless, and problems can arise that distract from their beauty. Some of these problems can result in long-term damage. All wood floors eventually deteriorate, but if they show signs of deterioration after just a few years, then it is likely that either something went wrong during the installation or that the floor was not properly maintained. This article is a brief guide to some of the most common issues with wood flooring and how to avoid or repair them.

Improper Prep Before and During Finish Application

Before a finish is placed, the floor must be properly sanded and cleaned to receive the finish. If not, the finish tends to peel. In addition, the finish must be abraded and cleaned in between coats, and adequate drying time allowed before a topcoat is applied. Failure to do any of these things can result in the finish peeling.

Improper Wood Floor Sanding

Improperly sanded floors have sanding grooves that are problematic to finish application. Wood floor finish settles at the bottom of these sanding grooves, but the tops of the grooves receive little to no finish. Consequently, surface deteriorates when the floor is exposed to foot traffic. To avoid this problem, try sanding bare boards to either 100 or 120 grit, depending on the finish.

Pay attention to the sanding materials you use in between coats of finish. Old abrasive screens or sanding pads can cause unattractive scratches that resemble spider webs on a wood floor. Additional finishes can accentuate these flaws. By the time you finish the job, poor sanding will be very obvious. To eliminate these scratches, the finish must be sanded past the coat where the scratches were first produced. Unfortunately, it can be challenging or even impossible to determine which coat of finish is scratched, so your best bet would be to start over and completely refinish the floor.

For proper wood floor sanding, sand between each finish application with high-quality abrasive pads that produce smaller, less apparent, and more numerous scratches. A suitable scratch pattern can greatly improve adhesion between finish applications. When sanding oil-based polyurethanes, use 150- to 180-grit pads, and when sanding between applications of water-based finishes, use 220-grit pads.

For the best finish, use the best sandpaper.

Inadequate Wood Floor Finish Drying Time

If coats of finish are added too quickly, the finish could take up to six months to cure. The result will be a wood floor with an aged appearance. Be sure to allow adequate drying time between finish applications.

Improper Wood Floor Maintenance

Thoroughly polished and sanded wood floors will need periodic professional services in order to maintain a pristine, welcoming appearance. Damage to the finish can happen in numerous ways. Grit on wood floors behaves like sandpaper with foot traffic. Unprotected furniture feet or unclipped pet nails can severely damage a finish, as well. Sometimes re-coating a slightly worn floor without completely removing the original finish can dramatically improve the appearance of the floor. On the other hand, it is better to sand down a floor to bare wood and refinish it if it has significant wear and severe scratches.

Other Common Problems

Other common problems with wood floors include peeling, grit and foreign particles in the finish, finish droplets, stains, gaps, cupping, buckling/sagging, and cracks. Let’s take a look at each of them.


The most frequent source of peeling is excess stain that is not removed from the floor before applying finish. Remove excess stain no later than three minutes after it has been applied and allow the floor to completely dry before applying the finish to avoid a buildup of stain residue. Don’t use several applications of stain too quickly. Allow it to dry.

Other causes of peeling include using finishes that are incompatible with each other or applying finishes to burnished wood, that is, wood that has become too smooth because of high-grit over-sanding.

When a floor peels, the best solution is to sand the floor down to the bare wood and start over. The issue might not be resolved by simply abrading the floor and applying a fresh topcoat, because furniture polishes, waxes, and oils used to clean wood floors can soak into the pores of the finish and may hinder new finish from successfully adhering.

Grit and Foreign Particles

Wet paint functions like a sizable piece of flypaper. Once the finish is complete, any dust or animal hair that gets inside of it will be more noticeable. Clean every surface in the room, including light fixtures and walls, before finishing the floor to keep debris from damaging the finish. Sweep the floor and wipe it down with a tack cloth, but never use tack cloths made for use on automobiles. They can have silicone in them, which jeopardizes the finish.

Line your applicator tray with an inside-out garbage bag. Strain the finish before being pouring it into the applicator. Finally, carefully wash and vacuum the applicator to eliminate any remaining loose fibers.

In the event that some debris penetrates the finish, make repairs by sanding the floor between applications of finish and then painting the floor with a fresh topcoat.

Finish Droplets

Moisture is always to blame when tiny polyurethane droplets collect around the borders of each floorboard. The polyurethane that flows into the spaces between the floorboards as the floor moves is what causes the droplets. This issue typically arises when a floor is being finished during the transition between dry and humid seasons. The boards expand as they acclimatize to the weather, pushing any uncured polyurethane out of the gap.

Poly droplets can be eliminated with a razor blade, a rag, and floor cleaner if they are discovered in time. If a mess has already been formed, either from walking on the droplets or from allowing them to dry, then each droplet must be manually removed with a razor blade from the floor before the entire surface is abraded in order to prepare for a new topcoat.


The most common cause of wood floor stains is pet accidents, although water can also be very destructive. A wood-floor cleanser can typically remove stains that have accumulated on a floor finish, but stains that have penetrated the wood surface must be sanded off. Stains that seep into the wood fibers are the most challenging to remove.

Two-part wood bleach can be used to restore the surface of a stained wood floor. Bleach the entire floor, not just a portion of it. (This requires a lot more work but results in a floor with a uniform gloss and hue.) After a couple of hours, neutralize the floor, and once it has dried, it can be sanded and refinished. Deeply soiled floorboards, particularly those that have been affected by pet urine, are typically replaced. However, removing stains with two-part wood bleach can also work.

This stain removal method comes with some negative aspects. The tendency of bleach to break down wood fibers can make wood more prone to denting. Additionally, there is no guarantee that the bleach will completely remove the stains from the wood, so wood flooring or floorboards may still need to be replaced.


Wood flooring is susceptible to shifting. Properly installed floorboards will hold tightly together during the humid seasons of the year and may show gaps during the dry seasons. The installation of flooring in overly dry places can also result in abnormal gaps, which are typically caused by the flooring being too moist when it is put in place. Examples include regions that receive a lot of sunlight, floorboards installed directly over heating ducts, and houses heated by wood stoves, which produce a dry indoor environment.

Gaps can be an aesthetic problem and should be fixed anytime they detract from the appearance of the entire floor. Fix abnormal gaps during the wettest season of the year when gaps are the smallest. Closing gaps when they are at their widest could result in a floor that buckles due to insufficient space for expansion.

Finally, never fill gaps with wood filler. Instead, use wood glue to attach small pieces of wood to the floorboard borders to create a repair. To avoid gluing any boards together, take care to just apply glue to one side of the sliver.


A board’s edges cup when the bottom is wetter than the top. The most frequent cause of cupping is the installation of flooring over a damp basement or crawlspace. Although cupping is more likely to occur on wide plank flooring, it can also occur on strip flooring.

Vapor retarders can improve the situation by reducing the rate of moisture migration but should not be considered a long-term fix for moisture issues. For strip flooring laid over traditionally constructed floors, use a vapor retarder. On floors over slabs, install broad plank flooring, or install radiant heating.

Once moisture problems have been resolved, some cupped floors flatten while others will remain irreversibly distorted. When the moisture content of the top and bottom of the boards is within 1%, a floor that does not lie flat will need to be sanded. To inspect the board bottoms, drill a moisture meter through the subfloor. Do not sand the peaked edges of a floor that has been cupped too soon, or you will risk having crowned boards once the wood is completely dry.

Buckling and Sagging

Too much moisture can cause wood flooring to expand to the point that it rises off the subfloor, causing shifts to door frames and separation of floor trim from walls. A floor may sag because of a flood, a moist basement, or from being installed when it was too dry. In any event, moisture is the primary cause of buckling and sagging.

Proper fastening can help prevent buckling and sagging. Nails should be the right size and spaced correctly. Using the proper size trowel during glue-down installations can help ensure a strong bond between the floors and the subfloor. Poor fastening can make buckling and sagging problems worse.

Some buckled floorboards can be refastened, but some need to be taken out. When feasible, reuse floorboards, but if the tongues and grooves are broken or the boards are damaged, you must replace them. Do not attempt to restore buckled flooring until moisture problems have been resolved and the moisture content of the floorboards and subfloor is at the proper level.


Compared to other types of flooring, factory-finished wood floors have more cracks, and a wood flooring nailer can easily ruin the finish on these boards. Most manufacturers produce adapters for their nailers that prevent the force of the nailer from concentrating on the surface of the floorboards.

Boards with a severely damaged edges should be immediately replaced during installation.

The faces of floorboards, whether factory-finished or normal, can develop cracks. Checks in the wood are usually to blame for this damage. Some species of wood are more prone checking and cracking than others.

Manufacturers can also cause cracking if the kiln dries the wood too soon. A manufacturer repair kit, which normally consists of wood filler, colored marker, and a bottle of finish, can be used to fix factory-finished boards. To ensure that the colors, tones, and sheen are exactly matched, replace the board, or fix the crack with wood filler before applying a layer of finish to the entire floor.

Follow these suggestions to resolve problems that diminish the beauty of wood floors or cause long-term damage. A properly installed and maintained wood floor can last a lifetime.