How to order sheathing and sheet goods
While there are many more products than are included here, once you know how to read and understand these sheathing and sheet goods grade stamps, you’ll be able to apply it to other sheet goods.
• APA – This is the official logo for APA – The Engineered Wood Association. It signifies that the manufacturer is a member of APA, and the panel has been manufactured and tested in accordance with APA standards.
Representing more than 80 percent of structural wood panel producers in the United States, APA is the leading grading organization for the industry. It develops standards for manufacture and testing of wood panels, including specifications identifying acceptable wood species, veneer quality, type of adhesives, amount of pressure that must be applied during forming, and temperature at which the adhesives must be set. Their grade stamp identifies each panel, lists its specifications and intended use.
• RATED STURD-I-FLOOR – A combined subfloor-underlayment, single-layer flooring intended for use under carpet and pad, the panels are available as plywood or OSB, with either tongue and groove or square-edge treatment.
• 24 OC SIZED FOR SPACING – Sturd-I-Floor panels come in various span ratings: 16, 19.2, 24, 32 and 48 inches. On this panel, 24 OC sized for spacing indicates this is designed for use over structural framing supports spaced a maximum of 24 inches on center (OC).
All floor and roof sheathing is designed to be applied with its long dimension perpendicular to (across) structural supports. The span ratings are based on the sheet being applied with its “strength axis” (long dimension) spanning at least three supports. While these span recommendations are widely accepted, actual maximum spans are established by local building codes.
• T&G NET WIDTH 47-1/2 – A square edged panel covers 48-inches, but when tongue and grove (T&G) panels are interlocked, the joint reduces the installed surface area by ½ inch.
• EXPOSURE 1 – This is a reference to the type of adhesives used to bond the panel and how well it will stand up to moisture. A panel with a rating of Exposure 1 is designed to withstand the effects of moisture resulting from construction delays and can be left exposed in applications such as soffit material under a roof eave where it is visible, but protected from the elements.
Exposure 1 panels are not suitable for use in applications where they would be fully exposed to weather, as extended exposure to moisture will cause the adhesives to break down, resulting in delamination.
• THICKNESS 0.703 IN – This is the thickness label. It gives the panel thickness in thousandths of an inch.
Because of varying regulations by the agencies with authority over the manufacture of wood-based panels – the U.S. Department of Commerce and the National Institute of Standards and Technology (NIST) – two statements of thickness are required in order to meet legal requirements.
• 000 – Mill identification number. Every APA member mill is issued a three digit ID number. If you have a problem with a batch of panels (rare, but it happens), this number can be used to trace the panels back to the mill where they were produced.
• PS 1-09 – Refers to Voluntary Product Standard PS 1-09 – Structural Plywood. Adopted by APA on May 1, 2010, the standard was developed under Commerce Department procedures.
The intent was to provide a common understanding among manufacturers, distributors and users of structural wood panels. It provides definitions for the types and grades of structural panels and lays out specific requirements for acceptable wood species and adhesives, veneer grading, panel construction, dimension tolerances and moisture content.
• UNDERLAYMENT – This panel is intended as a “single floor” application. One sheet of Sturd-I-Floor provides both the structural floor deck, as well as the underlayment for the floor finish.
• – APA trademark.
• PRP-108 –APA PRP-108 – Quality Assurance Policies for Structural-Use Panels – requires the mill to submit to an on-site inspection program. APA issues daily test reports and weekly audits to verify the mill’s products are in compliance with the quality standard. In addition, the mill must agree to employ an APA Quality Management System and certify mill staff through APA’s Certified Quality Technician program.
• 23/32 CATEGORY – This is the performance category. It gives the panel thickness in fractions of an inch. As discussed above, because two statements of thickness are required, this is the dimension that you’ll find listed in the International Building Code (IBC), International Residential Building Code (IRC), on plan drawings and in construction specifications.
You may be asking yourself: It’s a sheet of floor deck – why can’t they just call it ¾ inch?
When you order single application floor deck for a 24-inch OC floor system, your order should look something like this: 23/32-inch, OSB, 24 OC, Sturd-I-Floor, 100-sheets.
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.
An order for rated sheathing might read like this: APA Rated Sheathing, 4X8, OSB, 23/32-inch, rated 48/24, square edge, 100-sheets.
–By Michael Davis, Framing Square Construction, Conifer, Colorado