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I recently visited a home in the Southwest to conduct a site inspection on a wood flooring installation completed approximately three years ago. The homeowners complained that their wood floors had too much gapping. While some gaps are expected due to seasonal changes, this was more than the homeowners felt was normal. Of course, I immediately suspected moisture was the culprit.
Normally, gapping can be attributed to subfloor moisture vapor, an interior environmental problem or an acclimation problem. However, in this case, another factor was at play. The wood floor was a factory-finished exotic in a 5-inch-wide plank.
Normal moisture content (MC) for this wood floor species in the Southwest ranges from 8 to 10 percent. However, when I arrived at the site, the MC varied from 7.5 to 6 percent and even less. This wouldn't have been a problem had the wood been 2 1/4 -inch domestic strip. But this exotic species was wider and denser, so it was experiencing side-to-side movement due to moisture changes.
The gaps that had opened between the planks were between 0.02 and 0.06 inch. The width of a business card, for instance, is only 0.012 inch, but the gaps were obvious.
Due to the wide width of the planks and the home's dry interior environment, each plank had lost moisture and shrunk in width, causing the separations. The planks had a 0.5 to 4 percent lower MC than the 8 to 10 percent that was needed.
Several factors had contributed to this home's gapping problem, and they were all preventable. Increasing the humidity level inside the home would have increased the floor's MC and reduced the gaps.
In my many years in the hardwood flooring industry, I've seen similar scenarios with sabotaged wood floor installations played out again and again. Three factors, if managed shrewdly during home building and renovation projects, can significantly reduce these poor outcomes.
1) Proper Scheduling by the Builder
Builders and job-site superintendents have an extremely important role in ensuring successful wood flooring installations, because they are responsible for scheduling all aspects of building and renovation projects.
From the onset, it is important that realistic timeframes are established for all construction tasks, keeping in mind that hardwood flooring installers should be allowed to work only when normal living conditions are present in the home. All other trades should have completed their tasks before installation begins. Electricity should be turned on, doors and windows should be in place and the heating or air conditioning should be operational.
If work crews cancel and delays occur, the wood floor installation should be postponed until conditions are acceptable. After installation of the wood floors, if the house isn't going to be immediately occupied, it shouldn't be sealed up with no air exchange.
2) Point-of-Purchase Sales Information
Builders and installers should seek out informed sales personnel when purchasing hardwood flooring products. In my seminars, I've found that only about 10 percent of hardwood flooring sales personnel have read the manufacturers' instructions about the flooring products they sell. This is a problem, because it is essential that the salesperson communicate specific information to the builder or the enduser, such as what MC should be present in both the wood floor and subfloor at the time of installation.
The climate in which the home is located should be considered when the wood flooring is selected. A beachfront home in Hilton Head, S.C., should avoid having wide-width planks if doors and windows will be routinely left open, because the high moisture levels will create unwanted or accelerated wood movement.
Having informed salespeople is particularly critical in today's market, where exotic species are increasing in popularity and the widths are becoming wider. Salespeople need to be informed enough to tell consumers the "how, when and where" of wood products—that is, how to install the flooring, when to install it and where or in what location a particular product could be used for the best result.
3) Use Informed Installers
An installer's education is key (and certification is evidence that contractors take industry standards seriously). The installers must take into account the species and width of the wood flooring being installed. They should understand the importance of installing the wood floor after the home's temperature and humidity have stabilized and the HVAC system is operational. It's also extremely important that the installation supervisor check the job site's humidity levels and the MC of the subfloors before the hardwood floors are installed. The subfloors should be within the recommended levels for the type of wood flooring being used.
I've been on jobs where the installers were laying wood floors even though the home's concrete basement floor was yet to be poured. This is a recipe for disaster—as the concrete dries, water in the concrete will evaporate and be absorbed by the wood floors above, causing them to buckle, crack or split.
If the moisture of any subfloor is too high, installers need to wait and allow it to dry. If waiting is too difficult and the MC is near the appropriate level, products are available that can be applied to subfloors to reduce moisture-vapor migration to a reasonable level.
Above all, installers should always follow manufacturers' printed instructions and the NWFA's Installation Guidelines. Following some basic directions can make or break an installation.