As A Class "A" Roof Covering System
CHEMCO treated wood shakes labeled "Class B" may be installed over 1/4 inch (6mm) thick Dens-Deck Roof Board, manufactured by Georgia-Pacific Corporation. The Dens-Deck Board is fastened either to 1 inch (25mm) by 4 inch (102mm) spaced sheathing or 1/2 inch (13mm) plywood with exterior glue which shall be installed in accordance with the applicable code. Dens-Deck board requires a minimum of four fasteners per board to avoid panel shifting. Dens-Deck Roof board may be substituted with a minimum seventy-two pound mineral surface fiberglass cap sheet fastened to either 1 inch (25mm) by 4 inch (102mm) spaced sheathing or 1/2 inch (13 mm) plywood with exterior glue. If installed on spaced sheathing, the horizontal joints of the Dens-Deck must meet on the solid nailing surface. The mineral-surfaced cap sheet is installed mineral-surface side up with 2" (51mm) overlaps on sides and ends, and attached with sufficient number of fasteners to hold the sheet in place prior to installation of the shakes. Dens-Deck Roof Board and mineral surfaced fiberglass cap sheet must bear the label of a quality control agency accredited by ICBO ES. If installed on spaced sheathing, the horizontal overlap must meet on the solid nailing surface. (See figure A)
Roof Pitch and Exposure
Handsplit shakes should be used on roofs where the slope or pitch is sufficient to insure good drainage. Minimum recommended pitch is 1/6th or 4-in-12 (4" vertical rise for each 12" horizontal run. Maximum recommended weather exposure is 10" for 24" shakes.
Along the eave line, a 36" wide strip of Type 30 roofing felt is laid over the sheathing. The beginning or starter course at the eave line should be doubled. After each course of shakes is applied, an 18" wide strip of Type 30 roofing felt is laid over the top portion of the shakes extending onto the sheathing, with the bottom edge of the felt positioned at a distance above the butt equal to twice the weather exposure.
Hot dipped zinc coated nails or stainless steel staples are recommended. However, any U.B.C. approved corrosion resistant fasteners can be used. Use two for each shake, placing them approximately 1" from each edge, and high enough to be covered an inch or two by the succeeding course. Fasteners should be long enough to penetrate at least 1" or through the sheathing.
Valleys, Hips and Ridges
The roof valley flashing shall be provided of not less than No. 28 gauge pre-painted baked enamel metal applied over an underlayment of not less than Type 15 felt. The metal shall extend at least 11 inches from the centerline each way. Hips and ridges can be site-fabricated, or factory-formed hip and ridge units can be used. Weather exposure should be the same as that used in applying shakes in the field of the roof, and nails should be of sufficient length (usually 8d) to firmly attach the hip and ridge shakes to the underlying sheathing. Flashing and counter-flashing should be applied as illustrated.
BOTH RAW AND FIRE RETARDANT TREATED CEDAR PRODUCTS CONTAIN ACIDIC LEVELS THAT THROUGH INITIAL WATER RUNOFF CAN CAUSE STAINING AND CORROSION TO UNPROTECTED SURFACES. GUTTERS SHOULD BE USED AND IT IS STRONGLY RECOMMENDED THAT ALL GUTTER AND FLASHING MATERIAL BE FACTORY PRE-PAINTED BAKED ENAMEL. A THOROUGH LOW PRESSURE WASH OF THE ROOF IMMEDIATELY AFTER APPLICATION/INSTALLATION IS RECOMMENDED. CHEMCO IS NOT RESPONSIBLE FOR ANY DIRECT OR INDIRECT DAMAGE CAUSED BY WATER RUNOFF.