Wood Subfloor Specs.

1. All subfloor panels sheets should met the U.S Voluntary Product Standard PS1-95, Construction and Industrial or US Voluntary PS 2-04. IN Canada performance standard are CAN/CSA 0325.0-92 construction sheathing.
2. Any solid-board subflooring should be 3/4" x 5 1/2". Found in Group 1 dense softwoods, No. 2 common, kiln-dried less than 15 % moisture content.
3. OSB exposure 1 subfloor sheets and CD exposure 1 plywood are acceptable subflooring materials.

Subfloor Moisture in accordance to the National Association of Home Builders' Green Home Building Guidelines under Section 5.3.8: "NAB Model Green Home Building Guidelines.

1. Solid strip wood floor planks less than 3" wide, there should never exist a 4 percent difference in between the wood flooring and sub-flooring materials.
2. Solid strip wood floor planks 3" or wider there should never be a 2 percent difference in moisture content between wood flooring and sub-flooring materials.
3. If a difference does in fact exists, further acclimation time should proceed.

Subfloor Flatness

1. All Wood subfloors must be found flat, dry, clean and structurally sound. All floors should be free of squeaks and free of debris including protruding fastening systems.
2. Installations using mechanical fasteners of 1 1/2" or longer, subfloors should be flat within 1/4" in 10 ft or 3/16" in 6 ft.
3. Glue-down installations and installations using mechanical fasteners less than 1 1/2", the subfloor should be flat within 3/16" in 10 ft or 1/8" in 6 ft.

4.If high spots or dips are present, the following procedures need to take place:

A. High spots should be sanded down to specifications stated above
B. Dips should be leveled using a leveling compound approved for under wood flooring.
C.Any squeaks should be refasten.
D. Protruding fasteners are fixed by driving them deeper into the subfloor.

Panel Subflooring

1. Check for loose panels and refasten.
2. Make sure there is 1/8" expansion space in between non tongue-and-grooved panels. Using a circular saw this 1/8" space can be achieved. Never saw in between tongue-and-groove paneling.
3. The truss/joint spacing determines the acceptable thickness of the subflooring.
4.On truss/joint spacing of 16" or less, industry standard is nominal 5/8" CD Exposure 1 Plywood subfloor or 23/32 OSB Exposure 1 subfloor panels, 4' x 8' sheets
5. For truss/joint between 16" to 19.2" the industry standard is nominal 3/4" tongue-and-groove exposure 1 plywood subfloor panels or nominal 3/4" OSB Exposure 1 4' x 8' sheets. Panels should be glued and mechanically fastened.
6. For truss/joint systems spaced over more than 19.2" up to 24" require a nominal 7/8" tongue-and-groove CD exposure 1 plywood 4' x 8' sheets, or nominal 1"OSB exposure 1 subfloor 4' x 8' plywood sheets. Sheets should be glued and mechanically fastened.

Fastening and Spacing Specifications

1. Always follow the manufacturing directions for fastening and spacing.
2. Normally spacing and fastening standards for truss/joist systems are for 1/8" expansion space around the edges of each panel.
3. All edge swell should be flattened by using a edger sander.

Solid board subflooring

1. Subflooring should be 3/4" x 5 1/2", group 1 dense softwoods such as Larch, Fir, SYP, Doug, ect. No 2 common, kiln-dried less than 15% MC
2.The boards should not exceed a 6" width and should be installed on a 45 degree angle. The board ends should all be bearing on the joists fastened with8d rosin-coated or ring-shanked nails.
3. Not all types of wood flooring can be installed directly over solid-board subflooring.
4. Thin solid strip flooring has to have a 3/8" or better plywood underlayment installed over the solid board subflooring.
5. Parquet flooring for example may not be installed over solid board subflooring. A 3/8" or better underlayment panels should be installed using a 6" minimum grid pattern with ring-shanked nails.
6. See hardwood flooring manufacturer's recommendations for some engineered flooring cannot be installed over solid board subflooring.



Subfloor over concrete specifications

1. Normally a concrete slab will require a flatness specifications of 1/8" to 3/16" in a 10-foot radius.
2. If the slab is not within the standards because of high spots or low spots consider grinding or chipping high spots. All low spots should be filled in with an approved leveling compound.
3. While sanding the concrete floor, take into consideration of silica emissions caused by dust while grinding. OSHA recommends using approved dust-collection devices, or applying water to the floor before grinding. An approved respirator must be worn to minimize the silica dust intake.
4. See the moisture testing for specifications of moisture content on a concrete slab. Keep in mind that NWFA guidelines specify to use a relative-humidity test (ASTM F-D-4944-04), calcium chloride testing (ASTM-F 1869) or calcium carbide testing (ASTMD-4944-04) and MilSpec CRD-C154-77) to pinpoint moisture content on a slab.
5. When a concrete slab moisture emission is too high to glue a subfloor down, consider using a vapor retarder with a perm rating or 1 or less.
6. Concrete should be a minimum of 3000 psi. If the concrete psi is unknown use the floating subfloor method or contact the adhesive manufacture. (A good way to test this is take a nail and draw a line across the floor. If it leaves an indentation, it probably is lightweight concrete.

Installation of subfloor over concrete

Gluing a subfloor over a concrete floor

1. Always follow the manufacturer's recommendations for proper application, spread rate and trowel notch size. If a vapor retarder is necessary, follow the adhesives recommendations before doing so.
2. A vapor retarder is recommended anytime solid 3/4 wood flooring is installed over concrete.
3. Using a 5/8" CD exposure 1 plywood subfloor panels 4' x 8' sheets, cut the panels in 2' x 4' or 4' x 4' sections.
4. Score back of panels 1/2" deep on a 12" x 12" grid.
5. Apply adhesive approved for the installation of plywood, per the plywood manufacturer's recommendations.
6. Install the sections in a staggered joint pattern on the adhesive, with a 1/8" spacing between sheets, and a 3/4" minimum expansion space around all walls and vertical obstructions.

Nail-down Subfloor

1. Follow manufacturer's recommendations for proper subfloor.
2. On grade and below-grade applications, always add vapor barrier before applying underlayment. On an above-grade application, follow the manufacturer's recommendations.
3. A vapor barrier is recommended if a 3/4" hardwood flooring is to be installed over concrete. A good vapor barrier is a 6 mil polyethylene film.
4. Using minimum nominal 5/8" CD exposure 1plywood subfloor panels (CDX) 4' x 8' sheets fasten with powder-driven pins, pneumatic driven nails, screws, deformed pins, or any other approved fastener for concrete applications.
5. Allow a 1/8" spacing between sheets with staggered joints.
6. Allow a 3/4" minimum expansion space in between all surrounding walls or vertical obstructions. Follow pneumatic pressure or powder load instructions.
7. Fasten every 6" all along the edges and every 12" in the center.