Hardwood Flooring Over APA Panel Subfloors

APA panel subfloor spans for hardwood flooring are limited to maximum spacing of floor framing listed in Table 10. For improved stiffness, and to help eliminate floor squeaks when hardwood flooring is installed, construction in accordance with Code Plus Floors is suggested (see page 28). The National Oak Flooring Manufacturers Association (NOFMA) and the National Wood Floor Association (NWFA)* both recommend the use of minimum 23/32" OSB and plywood as a subfloor material.

Because hardwood flooring is sensitive to moisture, make sure subflooring panels are dry before hardwood is installed. Use a moisture meter to measure the moisture content of the subfloor. Do not install hardwood  unless subfloor moisture level is within a range consistent with the hardwood manufacturer's recommendations. If the home is built over a crawl space, make sure the crawl space is dry and well-drained. A 6-mil polyethylene vapor retarder should be installed on the ground in the crawl space.

Follow the recommendations of the National Oak Flooring Manufacturers Association (NOFMA) or National Wood Floor Association (NWFA) for storage, handling and acclimatizing the hardwood prior to installation on the subflooring.

*National Oak Flooring Manufacturers Association, P.O. Box 3009m, Memphis, Tennessee, 38173-0009; Phone (901) 526-5016.

National Wood Floor Association, 233 Old Meramec Station Rd., Manchester, Missouri 63021-5310; Phone (800) 422-4556.

Ceramic Tile Over APA Plywood Floors

Recommendations for several plywood floor systems suitable for application of ceramic tile are given in Table 12, based on specifications of the Tile Council of America. Note that maximum joist spacing for all systems is 16 inches, and that the plywood floor construction used depends on the tile installation system selected.

(a)APA RATED SHEATHING with Span Raging of 40/20 (19/32" panel).

(b) APA underlayment or sanded Exterior grade, except as noted.

(c) Attach Cementitious Backer Units (CBU) over a supporting plane of "Dry-Set" or latex-portland cement mortar with galvanized nails, screw-type nails or other corrosion-resistant fasteners. 7/16" minimum thickness CBU required for light commercial service.

(d) Leave 1/8" space at panel ends and edges. Fill joints with "Dry-Sets" or latex-portland cement mortar.

(e) Leave 1/4" space at panel ends and edges; trim panels as necessary to maintain end spacing and panel support on framing. Fill joints with epoxy mortar when it is spread for setting tile.

(f) Use No.15 asphalt felt or 4-mil polyethylene sheeting over subfloor. reinforce mortar with wire mesh.

(g) See Table 8, 10 or 11, as applicable, for panel fastening recommendations.