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The Problem
Last January I inspected a wood floor in a New England residence. The 3/4 -by-3-inch solid, factory-finished white oak floor had gaps between the boards.
The Procedure
The wood floor was in a new, single-story woodframe home with a full basement. The flooring was delivered (with an average moisture content [MC] of 8.5 percent) to the site in July and then acclimated for three weeks in the living room (at the time, there was no climate control operating in the house). Before installation, the MC of the flooring was checked and was at 10 percent, showing acclimation to the environment. The subfloor at the time was at 11 percent MC, and the framing was at 12 percent MC. The floor was installed by midAugust, the residence was occupied and the HVAC system turned on.
Following installation, the floor developed gaps between the sides of the boards. Gaps were minimal at first, but by the time of the inspection they had become noticeable, averaging 0.040 inch.
The environmental conditions in the home during the inspection were appropriate for performance of a wood floor. Flooring readings measured 6 percent MC, with the indoor environment at 31 percent relative humidity (RH) and 67 degrees Fahrenheit (humidification was in place and functioning).
The Cause
The wood flooring lost moisture during the seasonal dry period and developed gaps. However, "seasonal gaps" are just that: seasonal. They close during periods when the flooring gains adequate moisture. In this case, once the home was occupied, the home's environment was maintained between 30 and 50 percent RH year-round. This wood floor is unlikely to be in conditions again where humidity will reach levels necessary for the gaps to close entirely (in excess of 60 percent RH for a MC of 10 percent). These gaps are not seasonal. There will always be gaps in this floor, and when the interior environment is at the low end of its seasonal humidity range, the gaps will be prominent. The 10 percent MC of the wood at the time of installation will never again be reached as long as the homeowners use the year-round climate controls.
How to Fix the Floor
There is no way to restore the flooring to a closed, gap-free condition other than to maintain overly high humidity levels during the drier periods of the year, which is impractical and can even be unhealthy. In this instance, the flooring was removed and replaced.
In the Future
It's critical to identify the expected year-round interior environmental conditions and account for them prior to installing the flooring. This requires looking beyond the MC of the wood and associated structural components at the time of installation (the levels may look fine at the specific point in time when they are collected). The expected impact of environmental controls such as air conditioners, humidifiers and dehumidifiers, as well as the cyclical changes in humidity in that geographic region, must be factored in.
When combined, these factors determine suitable installation conditions for the flooring and its future environment. Don't mistakenly think that because flooring has been acclimated prior to installation that it is has been acclimated correctly and that installation can proceed. To ensure a successful wood floor installation and a satisfied customer, all variables relative to moisture must be identified and addressed.