Exterior type plywood is also used as a wall covering. The plywood sheets are made with a plain or grooved surface and are usually applied vertically. The joints may be V-grooved or flush or may be covered with batten. Plywood is available with a resin-impregnated kraft paper laminated to the face. This provides a smooth, mois-ture-resistant surface which resists checking or splitting after painting.
The minimum thickness of plywood applied as sheathing is 1/4 in. (6 mm). It may be applied directly to unsheathed wall framing. The minimum thickness used is ^4 in. (6 mm) for stud spacings of 16 in. (400 mm) on centre and 5/16 in. (8 mm) for spacing of supports up to 24 in. (600 mm) on centre. This assumes the face grain is installed at right angles to supports. Where the face grain is installed parallel to supports the minimum thickness Is 5/16 in. (8 mm) and 7/16 in. (11 mm) for studs spaced at 16 in. (400 mm) and 24 in. (600 mm) respectively.
After the plywood panels are cut and fitted, all edges should be protected with a suitable paint or sealer before Installation. A '/8 in. (2 to 3 mm) space between the sides and ends of the panels and butted ends of the battens will permit expansion without bulging. Vertical joints are filled with caulking or covered with a batten. Horizontal joints are flashed or lapped at least 1 in. (25 mm).
The edges of plywood panels should be supported and fastened with corrosion-resistant nails, usually 2 in. (51 mm) long. The nails are spaced 6 in. (150 mm) along the edges and 12 in. (300 mm) at intermediate supports.
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