By Scott Taylor

As wood flooring professionals, we all have a story about meeting with a homeowner who has found an objectionable gap(s) in their wood floor. A majority of these interactions can be avoided during the sales process by providing the customer with education about the importance of consistent relative humidity and temperature. Other factors can play a role, of course, such as species and width of the flooring.

To answer the inevitable question, “is this normal?” we have to understand why a floor will perform as it will. Wood is hygroscopic, which is defined by Merriam-Webster Dictionary as, “taken up and retained under some conditions of humidity and temperature.”

When a wood floor is exposed to an elevated relative humidity (RH), (NWFA guidelines suggest 30%-50% RH and 60º-80º throughout the year), it will start to expand if the RH is consistently elevated. When that same floor is exposed to a drier environment (typically during the heating season), the floor will contract. This contraction is typically due to the flooring losing moisture, resulting in the gaps. This is typical, but not always the case as there could be some other contributing factors. For this article, we will focus on the ambient environment (jobsite conditions) being the cause of the contraction.

The first question you should ask the homeowner is, “When did you notice the gaps?” If he or she states that gaps were noticed a month into the heating season, it’s very likely the contraction is due to the floor losing moisture resulting in the dimensional change of the individual boards. When a wood flooring professional is called to determine if the gaps are normal, they should take moisture readings and compare those to the moisture readings that were documented during the installation process (one of the many reasons to document jobsite conditions).

If the moisture readings are lower than when the floor was installed, it can be easily determined that the flooring has lost moisture resulting in the face of the flooring contracting. Besides the moisture content, it would also be beneficial to measure the face of the flooring. For example, if the product installed was 3” and is now 2 15/16” you know that the flooring has lost moisture in addition to taking moisture readings. These gaps can be minimized if the homeowner supplements their environment with a humidification system.

The newly rewritten Problems, Causes, and Cures (page 30) sums it up in a brief but to the point definition. DEFINITION: Gaps that appear between individual boards, opening and closing with seasonal humidity changes. Wider boards can experience wider gaps. The gap size is directly related and proportional to the board width.

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