Hardwood Floors Oct/Nov 2019

By Tony Morgan

CONCRETE MOISTURE MEASUREMENT If a contractor plans to install a wood subfloor above a concrete slab in a new or existing home, it’s necessary first tomeasure the moisture conditions within the slab. Excessive moisture in a slab can damage a wood subfloor and, in turn, an engineered wood floor. To accurately assess moisture conditions in a concrete slab, one commonly specified test is the ASTMF2170 relative humidity (RH) test.This test uses sensors or probes tomeasure the RH at a specific depth within the concrete – 40 percent of the slab’s thickness for a slab drying fromone side, or 20 percent for a slab drying from two sides. Scientific research confirms the reliability and accuracy of the RH test at these depths.The readings will most accurately predict the slab’s point of equilibrium, andmoisture condition that will exist within the slab after the flooring installation. Before installing a wood subfloor, a minimum class I vapor retarder meeting NWFA InstallationGuidelines should be placed on the slab to protect the subfloor and the flooring frommoisture. How to Install Nail-Down Engineered Wood Flooring When there’s a wood subfloor in place in the form of plywood or OSB, then a nail-down or staple-down installation is a common way to go. Required Tools Nail-down installations require additional tools, including a specialty flooring nail gun, saws, and routers. These are essential to complete the job successfully. You also will need a chalk line and nail set, power drill, nails and underlay paper, miter saw, table saw, back saw/door jamb cutter, safety glasses, and dust masks. Jobsite Preparation Installing wood flooring should always be one of the last jobs on any construction or remodeling project. The contractor,

ENGINEERED FLOORING REQUIRES ACCLIMATION

Just like solid hardwood flooring, engineered flooring needs to be properly aligned with its environment before installation. Consult the specific flooring manufacturer for their requirements. Do not store engineered wood flooring in garages or where humidity levels are higher. To allow for proper acclimation, the heating/air conditioning (HVAC) systemmust be capable of maintaining the requirements set forth by the flooring manufacturer. According to NWFA Installation Guidelines, the HVAC system should be operational for a minimum of five days prior to installation at a temperature between 60°F – 80°F and a relative humidity level should be controlled between 30 – 50 percent at all times prior, during, and after installation. To ensure the flooring is properly acclimated and has achieved equilibriummoisture content (EMC) with the surrounding ambient conditions, you need to measure the MC in the wood planks. Whether installing on a concrete or wood substrate, always reference the NWFA Installation Guidelines for the appropriate method of moisture testing. According to the NWFA guidelines, moisture content of the wood subfloor should be no more than 13 percent (specifically in humid geographic regions). And, there should be no more than 2 percent MC to 4 percent MC difference (depending on flooring plank width) between properly acclimated wood flooring and the wood subfloor.

Tip: Test the subfloor moisture in several locations taking note of higher readings. Higher readings indicate a moisture problem that needs to be addressed before installation can begin.

the magazine of the national wood flooring association

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