For boat-building applications, a special grade of plywood, APA Marine Exterior, is available. Marine-grade plywood is a premium panel using the same fully waterproof glues as regular Exterior plywood, but manufactured with only Douglas-fir or Western Larch veneers, and with additional restrictions on veneer grade, core gaps, patches and other characteristics. The grade of all plies of veneer is B or better. B-grade veneer may have knots but no knotholes. A-grade veneer has no knots or knotholes. Both A and B grade may contain wood or synthetic patches. Panels are sanded on both faces. The maximum core-gap size permitted is 1/8 inch. Its exposure durability rating is EXTERIOR and the glue used is a fully waterproof structural adhesive. It is considered a "premium" panel grade for use in situations where these characteristics are required.
Marine-grade plywood is not treated with any chemicals to enhance its resistance to decay. If decay is a concern, it should be pressure-preservative treated to an appropriate standard. The detailed description of veneer grades and Marine-grade plywood is contained in Voluntary Product Standard PS 1-95 Construction and Industrial Plywood.
Marine grade should be used where bending strength is important, such as boat hulls. Basic Exterior-type plywood may be used for most other applications in boat construction. Plywood panels rated as Exterior but not Marine, such as A-B, A-A or C-C Exterior, may contain any other permissible species and contain C-grade veneer. Unless specially improved, C-grade veneer is permitted to contain knots and knotholes up to approximately 1-1/2 inches across, and the inner plies may have core gaps up to 1-inch wide.
||- Grade: AB|
- Face Veneer: A grade Douglas Fir (9 single plugs maximum)
- Core Veneer: B grade or better Douglas Fir solid core
- Back Veneer: B grade Douglas Fir
- Adhesive: NAUF exterior, fully water resistant phenolic glue
- Sanding: Fully Sanded
- Patching Repairs - epoxy, no defects on faces, full sand and no edge putty
- End Stamp: AB-EXT-PS 1-09-Marine-PTL-#
- Fully water resistant phenolic resin
- No open defects on faces Minimal core gaps
- Dimensionally stable
- NAUF (No added urea formaldehyde)
- Can be specified FSC certified panels