Hardwood Floors December 2017/January 2018

SOLID PLANK INSTALLATION Solid plank wood oors can be installed successfully above-grade or on-grade, but are not recommended for installation below-grade. Solid plank ooring should be installed perpendicular to the joists, or on a diagonal for any single layer sub oor. (See NWFA Installation Guidelines for exceptions to this rule.) Ensure the environmental conditions of the space and the moisture content of the substrate coincide with the moisture content of the ooring (and when applicable, the manufacturer’s requirements). In general, there should be no more than 2 percent di erence in moisture content between properly acclimated wood ooring and wood sub ooring materials. As a general rule, a 3/4” expansion space should be le around the perimeter and at all vertical obstructions. Since solid wood doesn’t shrink/swell notably in its length, 3/4” may be overkill on bu -end walls. To minimize expansion on oors wider than 20’, or depending on geographical area, interior climate control, and time of the year, expansion may need to be built into the oor itself (washer rows). Undercu ing vertical obstructions may assist in gaining the required expansion space. For glue-down solid plank flooring over concrete: • Moisture control systems are always strongly suggested. • Use an adhesive and/or moisture control system approved by the ooring manufacturer. If none is recommended, use a system that matches the requirements of the space the ooring is going into. • Follow the installation procedure recommended by the adhesive manufacturer, which includes sub oor moisture test methods and limits, spread rate, trowel size, open time, working time, ash time, use of rollers, and use of straps/tape as necessary. Mechanically fastened solid plank floors: • Where necessary add a vapor retarder over the wood sub oor. • Nailing: Blind-nail through the tongue using 1-1/2” to 2” fasteners. Fasteners should be spaced every 6 – 8”, and 1 – 3” from each end. Some wood ooring installations may bene t from a decrease in spacing between fasteners, as long as it does not cause spli ing of the tongues. Higher gauge fasteners (18 gauge) may require, and allow for a tighter fastener schedule.

ENGINEERED PLANK INSTALLATION Engineered plank wood oors can be installed successfully on, above, or below grade level. Engineered plank ooring should be installed perpendicular to the joists, or on a diagonal for any single layer sub oor. (See NWFA Installation Guidelines for exceptions to this rule.) Ensure the environmental conditions (temperature and humidity) of the space and the moisture content of the substrate coincide with the manufacturer’s requirements for the ooring going in. Check the moisture content of the substrate to ensure it is aligned with the ambient conditions (at EMC). As a general rule, the engineered ooring material thickness dictates the expansion space le around the perimeter and at all vertical obstructions. Engineered ooring can shrink/swell both in width and length, so expansion is critical in all directions. To minimize expansion on oors wider than 20’, use of t-molding or other transition pieces recommended by the ooring manufacturer may be necessary, depending on geographical area, interior climate control, and time of the year. Undercu ing vertical obstructions may assist in gaining the required expansion space. For glue-down engineered plank over concrete: • Moisture control systems are always strongly suggested. • Use an adhesive approved by the ooring manufacturer. • Follow the installation procedure recommended by the adhesive manufacturer, which includes sub oor moisture test methods and limits, spread rate, trowel size, open time, working time, ash time, use of rollers, and use of tensioners/ tape as necessary. Mechanically fastened engineered plank floors: • Where necessary, add a vapor retarder over the wood sub oor. • Use the appropriate fastener and a nail gun required by the ooring manufacturer. • Typical fasteners used for engineered ooring are narrow crowned (under 3/8”) 1 – 1-1/2” staples or 1 – 1-1/4” hardwood ooring cleats, spaced every 3 – 4” with staples, every 4 – 6” with cleats, and within 1 – 2” of end joints. Some wood ooring installations may bene t from a decrease in spacing between fasteners, as long as it does not cause spli ing of the tongues. Floating engineered plank: • Sub oor atness and perimeter expansion are critical to the success of a oating oor. • Install a vapor retarder or resilient pad underlayment as directed by the ooring manufacturer. • Floating plank engineered ooring is normally edge-glued or edge-a ached with a self-locking mechanism. (For edge-glued products, use an adhesive approved by the ooring manufacturer.) • Perimeter expansion space at all vertical obstructions is critical. A oated wood oor becomes one monolithic unit and should not be bound at any point. It is also necessary to use t-molding or other transition pieces throughout a oated oor installation.

the magazine of the national wood flooring association

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