Plywood Grade Stamp Explained

APA Stamp

The span rating indicates the maximum inches between supports (i.e. joist, truss etc) that the panel may be applied. If there are two numbers, the first refers to roof applications, the second to floor applications.

The Exposure Durability Classification defines whether the panel should be
used for interior or exterior applications:

  • Exterior panels have a fully waterproof bond and are designed for
    applications subject to permanent exposure to the weather or moisture.
  • Exposure 1 panels are designed for protected construction
    and industrial applications and can be exposed to the elements for a short
    time, but not permanently.
  • Exposure 2 panels are intended for protected construction
    and industrial applications where the potential for conditions of high
    humidity and water leakage exist.
  • Interior panels are manufactured with an interior grade
    glue and are intended for interior applications only.

The thickness of the panel is also included on the stamp.

Installation Instructions

Consult with a professional installer, licensed contractor or, for detailed application and installation instructions, write to:

APA-The Engineered Wood Association
7011 S. 19th Street
Tacoma, WA 98466-5333
(253) 565-6600
www.apawood.org

Pine Finishing Recommendations

Prime and paint or use two coats of opaque (solid color) stain. Use acrylic
latex paint only; oil based paint is not recommended.

When used for an outdoor application, it is important to prime and paint all
exposed surfaces including edges.

IT IS RECOMMENDED THAT REPAIR WORK BE PERFORMED BY A
LICENSED PROFESSIONAL.

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FRT (Fire Retardant Treated) Plywood, What is it?

 FRT (fire retardant treated) Plywood

FRT plywood is a sheathing  treated with a chemical to prevent flame spreading in the event of the fire. It was used on townhouses and condos roofs, 4 feet on each side (sometimes more) of the walls separating each individual unit in the late 1970’s to early 1980’s. Some types of this plywood have been identified as defective, but not all of them! It was discovered that a chemical reaction occurs at a lower attic temperature than expected, which weakened the plywood and caused structural failure. A visual inspection may not be able to tell you whether the materials used on a roof are defective. FRT plywood is usually darker in color. Look for the following:

  • A white powdery substance or stain on the plywood visible in the attic, caused by the leakage of chemicals
  • A darkening of the wood, resembling black coffee
  • A charred appearance to the plywood
  • Plywood that becomes brittle or cracks and crumbles easily
  • A leak in the roof
  • The roof on the exterior might appear wavy
  • FRT plywood cannot be repaired. If the FRT plywood on the roof is defective, it must be replaced.
IT IS RECOMMENDED THAT REPAIR WORK BE PERFORMED BY A LICENSED PROFESSIONAL.
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