Seasonal Moisture Content Fluctuations in Wood Floors -- Cupping, crowning and gapping between wood floor planks/strips typically is caused by moisture content fluctuations in the product, usually as a result of seasonal climate changes or exposure to a hidden source of moisture. In the pairs of figures on the map, the first represents the average January percentage of moisture content in wood products used indoors, while the second expresses the products' average moisture content in July. Source: U.S. Department of Agriculture, Forest Products Laboratory.

As is true of any floor covering, mishaps can mar the installation during the course of its lifespan. But one of the principal reasons why today’s consumers choose hardwood for their new homes, or as a replacement for an existing floor covering, is the product’s longevity and capacity for renewal.

Believe it or not, most of these same consumers espouse the idea that wood floors which have been exposed to a source of uncontrolled water will require complete replacement because of the disfiguration that results. Obviously, the amount of water exposure, the gross square footage of the affected portion of the floor and — most of all — the duration of the exposure ultimately determine the repair and restoration procedure required for the floor. The homeowner may require some reassuring “hand holding” from the dealer/contractor during restoration work.

It’s also important to inform homeowners of the personal contribution they’ll be required to make during the process. Your challenge is to overcome their narrow focus on making this temporary problem go away as soon as possible.

Homeowners need to be convinced that an integral part of the restoration process requires waiting for the floor to completely dry and stabilize to it original moisture content. Their patience and understanding of this requirement is vital to the ultimate success of the restoration procedure.

Stabilization of the material and environment has always been a prerequisite for hardwood installations. Before an original installation can proceed, the wood flooring must be acclimated to the jobsite environment. This rule still applies in a restoration situation.

When it comes to dealing with a hardwood floor that’s been exposed to excess moisture, arresting and stabilizing the undesirable condition will require the dealer/contractor to conduct a fact-finding mission to locate the source of the problem.

In new residential construction, obvious sources of moisture indoors — such as a leak from the roof or a break in a plumbing supply line to a fixture — are normally detected and corrected before the hardwood flooring dealer/contractor arrives on the scene to install his products. When moisture affects the floor after installation, the homeowner may view your follow-up inspection report and findings with skepticism. Many will express the opinion that something other than the floor is all wet — namely, your report.

Convincing the customer that a moisture-related problem can and will exist — even in the absence of a raging river running through a portion of the hardwood floor installation — may constitute a challenge in itself. Most homeowners tend to think that the hardwood product is defective whenever the source of moisture isn’t obvious or easily detected.

By taking several moisture readings throughout the installation, you can document any and all areas in the floor that are beyond the accepted industry standards for allowable moisture content. In most cases, you can show the homeowner the numerical readings displayed on the moisture meter and demonstrate how they decrease as you move farther away from the moisture’s source.

The most common moisture-generating culprits include exterior doors, usually in need of threshold repairs or replacement, that occasionally allow wind-driven rain to penetrate indoors. Another prominent but often-overlooked moisture source is a deteriorating wax ring used as a seal between the toilet bowl and sanitary soil pipe.

Probably the source of water leaks that most often goes undetected is the dishwasher. This is becoming an increasingly common moisture source because, as we all know, kitchens have become a hot area for hardwood floor installations.

I’ve just identified a few of the most common origins of potential moisture-related problems in any hardwood floor installation. The following is my five-point guideline of remedial cures.

1. Determine the source of moisture and advise the customer. Use a moisture meter to conduct multiple moisture content readings at various locations across the floor. If the floor requires relief for expansion while drying, remove a row of flooring along the wall line. Reinstall the row when the floor is again stabilized and thoroughly dry.

2. After the floor has dried and stabilized, determine the extent of repairs that will be required. Depending upon the amount of water to which the installation was subjected, the floor may revert back to its original condition prior to moisture exposure. In such instances, waiting can be a significant factor in avoiding unnecessary repairs.

3. In the event that the wood planks or strips become permanently cupped from exposure to moisture, the installation will require resanding and refinishing. Bear in mind that premature sanding will transform a cupped floor into a crowned floor once the installation is fully dried and stabilized (see the “Three Steps of Crowning” diagram).

4. Depending on the size of area that is distorted, affected planks/strips may be replaced with new flooring that matches the existing grade and species. After the repair, resand and refinish the replacement pieces to blend with the existing flooring.

5. If the installation was prefinished at the factory, obtain additional product from the manufacturer through an authorized distributor and replace the damaged planks or strips. Or better yet, ask the homeowner for any extra pieces of the product leftover from the original installation. Again, the size of the affected area and the amount of replacement material required will determine whether or not sanding and finishing will be required.

When it comes hardwood floors and water, you just may — somewhere at some time — receive a call from a customer who bellows out, “Surf’s up!” Wood or Wood Knot invites you to “catch a wave.” Just don’t get thrown overboard in the process.