Hardwood Flooring February March 2018

Glue-Down When direct gluing a wood subfloor over concrete, follow the adhesive manufacturer’s recommendation for moisture requirements and limitations, type of adhesive, application method, trowel notch type, and spread rates. When the adhesive requires, add a moisture control system before applying the adhesive. Use a minimum 3/4” (23/32, 18.3 mm) subfloor panel cut to smaller 2’ x 8’ or

4’ x 4’ sections. Kerf the back of the panels 1/2 the thickness of the material (3/8”) on a 12” x 12” grid. Lay sections in a staggered joint pattern in the adhesive, with 1/8” spacing between sheets, and 3/4” minimum expansion space at walls and all vertical obstructions. Flatness tolerances should be to within 3/16” in 6’ or 1/4” in 10’ for nail down over the wood subfloor. Do not use flooring fasteners longer than 1 3/4” to be certain not to puncture the moisture control membrane.

Floating For floated wood subfloors installed on-grade and below-grade, be certain moisture control is taken into

account. This may be as simple as a 6 mil polyethylene plastic covering 100 percent of the concrete and brought up all walls, then trimmed after the floor has been installed. Use a minimum of two layers 3/8” (10 mm) CD Exposure 1 Plywood subfloor panels (CDX) in 4’ x 8’ sheets. Place the first layer with edges parallel to the longest starting wall. Lay the second layer so that no seams line up with the below layer. All of the

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