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Check the job site before delivery. Be sure the flooring will not be exposed to excessive periods of high humidity or moisture. The building should be closed in with outside windows and doors in place. All concrete, masonry, drywall, ceramic tile flooring and latex paint should be thoroughly dry. The exterior grade or slope should direct water away from the building. Basements and crawl spaces must be dry and well ventilated. In joist construction with no basement, outside cross ventilation through vents or other openings in the foundation walls must be provided with no dead air areas. A surface cover on the floor of the crawl space of 6 mil polyethylene film is essential as a vapor retarder in crawl space construction. In warm months, the building must be well ventilated. During winter months, heating should be maintained near occupancy levels at least five days before the flooring is delivered and maintained at that level after the floor is installed. The average moisture content of framing members and subflooring should be below 12%-14% before delivery of the flooring. Moisture contents above 12%-14% can cause moisture related problems. When job site conditions are satisfactory, have the flooring delivered and broken up into small lots and stored in the rooms where it will be installed. Open the boxes. The flooring acclimates faster when the boxes are opened. Allow 4 to 5 days or more, for the flooring to become acclimated to job site conditions. GENERAL INSTALLATION INSTRUCTIONS The following general instructions apply to strip flooring laid on board or plywood-over-joists subfloors, on plywood-on-slab subfloors, and on screed subfloors. Consult your hardwood flooring professional or the National Wood Flooring Association for detailed installations instructions. Location and straight alignment of the first course is important. Place a mark 3/4" plus the face width of flooring (2 1/4", 3 1/4”) plus 1/4” for the tongue on the end wall near a corner of starting wall. Snap a chalk line between these two marks. The 3/4” gap between the first row of flooring and the wall is needed for expansion space. Leave a space of 1/2” between the wall and each end of the row. Align the tongues of the first row of flooring with this chalk line. Drive 6d or 8d flooring nails or casing nails (galvanized or screw shank hold best) 1" from the grooved edge. Nails should be driven into the face of the boards and counter sunk (face nailing). Pre-drilling nail holes will prevent splits. Also, blind nail this starting strip through the tongue according to the NWFA nailing schedule. After the starter row, fit each row of successive strips snug, groove-to-tongue. Blind nail through the tongue along the length of the strip. After the second or third run is in place, you can change from a hammer to a floor-nailing machine. Before nailing, rack the floor by talking the boards out of the boxes and laying out several rows of flooring. This allows you to watch your pattern for even distribution of long and short pieces, to avoid clusters of short boards and to discard any unwanted boards. From one row to the next, stagger the end joints at least 6” apart. Work from several boxes at a time. Continue installing across the room, ending up on the far wall with the same 3/4" expansion space as on the beginning wall. It may be necessary to rip a strip to fit. Blind nail by hand where the nailing machine cannot be used. Face nail the last rows when unable to blind nail by hand. Use an offset pry bar or lever device to tighten these last face-nailed rows. Use a slip-tongue to reverse direction. Glue and blind nail the slip tongue. After the entire floor is in place, nail quarter-rounds or shoe mouldings to the baseboard, not the flooring. INSTALLATION OVER WOOD JOIST CONSTRUCTION If the subfloor is plywood, 5/8" or 3/4" performance rated products are preferred. Also, 3/4" OSB is a comparable substrate. Install subfloor panels as recommended by the panel manufacturer. Laying plywood on a diagonal to the direction of the finished floor will help prevent cracks associated with panel edges. They should be installed with the grain of faces running across the joists. Stagger plywood joints every 4' by cutting the first sheet of every other row. Nail every 6" along each joist, starting from the center of the plywood sheet. On an existing board or plywood-over-joists subfloors, start by re-nailing any loose areas and sweeping the subfloor clean. Direction of finish flooring should be at right angles to the joists. This is generally the longest dimension of the room or building and gives best appearance. INSTALLATION OVER A CONCRETE SLAB Hardwood flooring can be installed successfully over a slab, which is on-grade, or above grade. Below-grade installations are not recommended. The slab must be sound, dry and flat with a trowel finish. If necessary, grind off any high spots, fill low spots, clean up grease, oil and other contaminants, and sweep clean. If the slab is "mealy" and excessively dusty, it may not be of proper strength. Vapor Retarders: Consult the NWFA installations instructions or your hardwood flooring professional. To be certain normal slab moisture does not reach the finished floor, a vapor retarder must be used on top of the slab. Adequate vapor retarders are 2 layers of 15 lb. asphalt paper or 4-6 mil polyethylene film. These systems are not “moisture barriers”, only “moisture retarders”. This is not a solution for concrete slabs with severe moisture problems. New concrete is heavy with moisture, an inherent problem for wood. Proper on-grade slab construction requires a vapor retarder such as 6-mil polyethylene film between the gravel fill and the slab. While this prevents moisture entry through the slab, this membrane also retards curing of the slab. Always test for moisture, even if the slab has been in place for many years. Slabs younger than 60-days are generally too wet for flooring installation. This method uses 3/4" or thicker sheathing grade exterior plywood as the subfloor over the appropriate vapor retarder. Loose lay 3/4" plywood panels over entire floor. Laying plywood on a diagonal to the direction of the finished floor will help prevent cracks associated with panel edges. Stagger plywood and joints every 4' by cutting the first sheet of every other run in half. Leave 3/4" space at all wall lines and 1/4" to 1/2" between panels. Fasten the plywood with a powder-actuated concrete nailer or hammer-driven concrete nails. Be sure to flatten out the plywood, start at the center of the panel and work toward the edges. Use at least nine nails per panel or more to fasten securely. An alternate method is to glue the 3/4" plywood over the vapor retarder systems. Consult the NWFA or the adhesive manufacturers for instructions. This method uses, as a nailing base flat, dry 2" x 4” or 2” x 3” screeds, sometimes called sleepers, as a nailing base. They must be preservative treated with a product suitable for interior installation. Screeds are laid on their flat face in rivers of mastic, 12" on center and at right angles to the direction of the finished floor. Be sure there is enough mastic for 100% contact between screeds and slab. Over the screeds lay a 6-mil polyethylene film vapor retarder with edges lapped a minimum of 4”-6”. The finish flooring will be nailed to the screeds through the film. End joints need not fall on the screeds, they can occur in between screeds. Ensure that the end joints are well spaced so that no two end joints in successive rows fall between the same two screds.
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