Subfloor must be flat
Make sure the panels are flat to within 3mm in 2m radius. If the panels are out of specification, consider sanding. When sanding, care must be taken to minimize the amount of dust produced. Best practice would include using dust-collection devices. Approved respirators should also be used to minimize the amount of dust inhaled.
Subfloor must be dry
For more information, please see moisture testing.
For panel products subfloors, check for loose panels and re-nail or screw down loose panels securely.
Ensure that there is proper expansion space (3mm) between the panels. If the subfloor panels are not tongue-and-grooved and if there is not sufficient expansion space, use a circular saw to create the specified space. Do not saw through joints on T&G subfloors.
Also check for delaminated or damaged areas and repair those areas as needed. Make sure the subfloor is free of debris before beginning installation.
Acceptable panel subfloors: Building regulations A structure:
On truss/joist spacing of 406mm o/c or less, the industry standard for single-panel subflooring is nominal 15mm CD Exposure 1 Plywood subfloor panels (Class 1 EXPOSURE 1) or 18mm OSB Exposure 1 subfloor panels, 1200mm X 2400mm sheets.
On truss/joist spacing of more than 406mm up to 488mm o/c, the standard is nominal 19mm T&G Class 1 EXPOSURE 1 Plywood subfloor panels, (Exposure 1), 1200mm X 2400mm sheets, glued and mechanically fastened, or nominal 19mm OSB Exposure 1 subfloor panels, 1200mm x 2400mm sheets, glued and mechanically fastened.
Truss/joist systems spaced over more than (488mm) o/c up to a maximum of (610mm) require nominal 22mm T&G Class 1 EXPOSURE 1 Plywood subfloor panels, (Exposure 1), 1200mm X 2400mm sheets, glued and mechanically fastened, or nominal 25mm OSB Exposure 1 subfloor panels, 4’ x 8’ sheets, glued and mechanically fastened or two layers of subflooring. Or brace between truss/joists in accordance with the truss/joist manufacturer’s recommendations and with recognised building codes. Some truss/joist systems cannot be cross-braced and still maintain stability.
For double-layer subfloors, the first layer should consist of nominal 19mm class 1 Exposure 1 Plywood subfloor panels , 1200mm X 2400mm sheets or nominal 19 OSB Exposure 1 subfloor panels, 1200mm’ x 2400mm sheets. The second layer should consist of nominal 12mm class 1 EXPOSURE 1 plywood subfloor panels, (Exposure 1) 1200mm X 2400mm sheets. The 12mm plywood should be offset by 12mm panel in each direction to the existing subflooring. The panels may also be laid on a diagonal or perpendicular, with 3mm spacing between sheets. Nail on a 305mm minimum grid pattern, using ring-shank nails or staples.
Fastening and Spacing Specifications
Follow the panel manufacturer’s recommendations for spacing and fastening.
Typical panel spacing and fastening requirements for truss/joist systems call for a 3mm expansion space around the perimeter of each panel, with panels fastened every 300 mm along intermediate supports.
Edge swell should also be flattened. This can usually be accomplished by using an edger sander.