common grade stamp
This common grade stamp is very similar to the Sturd-I-Floor stamp we looked at, but it’s on a panel of rated sheeting. APA Rated Sheathing is intended for use as subfloor, wall, shear wall or roof sheathing. Typically produced with square edges, tongue & groove rated sheeting is available, but rare.
• APA – This is the official APA logo.
• RATED SHEATHING – APA Rated Sheathing should be used for subflooring, walls, shear walls and roof sheathing.
• 48/24 – SIZED FOR SPACING – Two numbers separated by a forward slash indicate the span rating. The first number indicates the span for roof sheathing and the second for floor deck.
In this example, 48 indicates that this panel can be applied over roof framing members at 48 inches OC; 24 is the OC spacing for structural floor framing.
Explanations for the Exposure 1 Rating, Thickness Label and Mill Identification Number are the same as in the previous example.
• PS 2-10 –PS 2-10 Performance Standard for Wood-Based Structural Use Panels. This is another voluntary standard initiated by APA, under Commerce Department procedures. The reference to PS 2-10 in the grade stamp indicates the product meets the requirements of the standard.
PS 1-09, written in 2010, primarily addressed plywood, while PS 2-10, written in 2011, has a broader focus and covers structural plywood, OSB and other mat-formed panels, as well as composite panels. The standard classifies panels by bond (adhesive), span rating, performance category and grade. It also specifies required product test methods and quality certification programs.
• PRP-108 – The APA testing and quality control standard.
• HUD-UM-40 – This is the U.S. Housing and Urban Development (HUD) Building Product Standards and Certification Program for Plywood and other Performance Rated Wood-Based Structural-Use Panels. This five-page document basically says all structural wood panels used to construct HUD housing shall comply with APA PRP-108.
Construction sheathing stamps in Canada
The rest of the grade stamp is provided for Canadian consumers.
• CONSTRUCTION SHEATHING – This is the Canadian equivalent of the APA-designation rated sheathing and is for use as subfloor, wall, shear wall and roof sheathing.
• 2R48/2F24 – In 2R48, the 2 indicates that in order to achieve the R48 (roof, 48 inch OC) span rating additional edge support must be provided. This might be in the form of edge blocking or panel support clips, such as Simpson Strong-Tie PSCL. A designation of 1R48 would mean the panel would achieve its maximum span rating without the additional edge support and would usually be a tongue & groove product.
The 2F24 means that in order to be used at its rated span of 24 inches in a floor framing application either additional edge support or underlayment is required. A panel marked 1F24 would most likely be a tongue & groove product and would not require additional support or underlayment.
• 18mm – This thickness label is in metrics; 18mm is approximately 0.703 inch.
• CSA 0325-07 – CSA stands for Canadian Standards Association. Structural wood panels used in Canadian building construction must be certified to one of four product standards: CSA Standard O121 Douglas Fir Plywood, O151 Canadian Softwood Plywood, O153 Poplar Plywood or 0325 Construction Sheathing.
CSA 0325-07 Construction Sheathing is the adoption by Canada, with minor changes, of the NIST Voluntary Product Standard PS 2, Performance Standard for Wood-Based Structural-Use Panels.
• STRENGH AXIS – THIS DIRECTION – The final block of the grade stamp means all floor and roof sheathing is designed to be applied with the long dimension perpendicular (across) the structural supports. The span ratings are based on the sheet being applied with its “strength axis” (long dimension) spanning at least three supports.
Sample: An order for rated sheathing might read like this: APA Rated Sheathing, 4X8, OSB, 23/32-inch, rated 48/24, square edge, 100-sheets.