One of the most frequent questions people ask about wide plank flooring is, “Will the wide boards cup?” This is a good question that many people ask, so I want to try and address some of the causes of undesirable movement in wood flooring, particularly in wide plank flooring.

Undesirable Movement

Exposure to high moisture levels will cause wood boards to cup.

Cupping, warping, and bowing in wood boards is natural but there are ways to avoid and/or repair the wood before it is milled into flooring. The reasons wide wood boards will cup have more to do with how the wood was sawn, how it was dried, and the environment the wood is installed/stored in, than the width of the boards themselves. While cupping in a wide board is more noticeable, any size board can and will cup – it’s just a not as noticeable on narrower boards. Generally, any plank floor with 5″ or wider planks will show a considerable degree of cupping if they are not installed correctly, if the environment is not properly controlled, or if the flooring was stored for a considerable amount of time before installation. Essentially, it’s all about controlling the moisture levels the wood is exposed to.

Many manufacturers will mill their flooring and store it as inventory – this is a problem because the wood will take on some degree of moisture while in storage, and once the wood has been milled, cupping or warping is in most cases permanent and cannot be repaired. In our manufacturing facility we never machine the wood until it can be immediately delivered to the site after milling is completed. If the raw material had developed any cupping or warping while in our warehouse, it would be corrected when the wood is milled – producing perfectly flat planks.

The Environment

Proper sub-floor for installation over concrete.

As far as the environment of the home is concerned, the flooring must only be installed after the heating and cooling is operable in the home – this will help control the humidity levels in the home and make the environment suitable for installation. The surface on which the planks will be installed is also a factor in how much moisture the underneath of the floor may be exposed to.  Concrete, for instance, can transfer significant amounts of moisture to the underneath of the wood potentially causing cupping or warping. With the right sub-floor, hardwood planks can be installed on either on-grade, or above-ground slabs. Installation on below-grade slabs is not recommended.

Installation

Once the flooring arrives at the home, installation should begin immediately, unless installing over concrete (in this case most recommend the wood should acclimate for a period of 7-10 days before installation with a relative humidity level of 45%) . However, if short-term storage is absolutely necessary, it must be stored in a humidity controlled environment or it will likely absorb too much moisture which will result in cupping and/or warping. Storing wide plank flooring in a garage or basement is not acceptable.

The planks must be glued down with an approved adhesive, in addition to nailing. An approved adhesive will be able to absorb some movement in the sub-floor due to temperature changes and settling of the home, thereby keeping a good hold on the planks and helping them not cup or warp significantly.

Finishing

The final stage is the finishing. Most wide plank floors are finished with either Tung oil, or polyurethane. These finishes will help to seal the wood so that it does not absorb excessive moisture.