Applying Fire Retardant Cedar Shakes

 

Installing a Class "C" Roof Covering System

CHEMCO pressure treated western red cedar shakes labeled "Class C" are applied over a substrate of 1 inch (25mm) by 4 inch (102mm) spaced sheathing boards or not less than 1/2 inch (13mm) thick plywood with exterior glue, which shall be installed in accordance with the applicable code.

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.

Roof Application

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.

Fasteners

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 one inch 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 3/4" or through the sheathing. The butts of the shakes should project from 1 1/2 to 2 inches from the first roof board so that the rainwater will spill into the gutter or to the ground without working down the side of the building. Individual shakes should be spaced about 1/4" to 3/8" apart to allow for possible expansion. These joints or spaces between shakes should be broken or offset at least 1 1/2" in adjacent courses and should be kept out of direct alignment in alternate courses.

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.

WARNING:

Both raw and fire retardant treated cedar products contain a level of tannic acid that can cause corrosion to unprotected metals and concrete surfaces. Pre-painted galvanized or pre-painted aluminum gutters are recommended. Initial water runoff over both raw and fire retardant cedar can cause staining. A low-pressure wash of the roof immediately after application is recommended. CHEMCO is not responsible for any direct or indirect damages caused by water runoff.

Installing a Class "B" Roof Covering System

CHEMCO pressure treated western red cedar shakes labeled "Class B" are applied over a substrate of 1 inch (25mm) by 4 inch (102mm) spaced sheathing boards or not less than 1/2 inch (13mm) thick plywood with exterior glue, which shall be installed in accordance with the applicable code.

WARNING:

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.

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