Applying Fire Retardant Cedar Shingles

 

Installing a Class "C" Roof Covering System

CHEMCO pressure treated western red cedar shingles 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

Proper weather exposure is important, and depends largely on roof slope. On roof slopes of 4" rise in 12" horizontal run (pitch 1/6) and steeper, the standard exposures are: 5" for 16" shingles; 5 1/2" for 18" shingles; and 7 1/2" for 24" shingles. On roof slopes less than 4/12 to a minimum of 3/12, reduced exposures are recommended.

Roof Application

Shingles normally are applied in straight, single courses. Shingles must be doubled at all eaves. Butts of first-course shingles should project 1 1/2" beyond the first sheathing board. Spacing between adjacent shingles (joints) should be 1/4". Joints in any one course should be separated not less than 1 1/2" from joints in adjacent courses, and joints in alternate courses should not be in direct alignment.

Fasteners

Hot dipped zinc coated nails or stainless steel staples are recommended. However, any U.B.C. approved corrosion-resistant fasteners can be used. Apply each shingle with two (only) fasteners. Each fastener should be placed not more than 3/4" from the side edge of the shingle and not more than 1" above the exposure line. Use 3d (1 1/4") nails for 16" and 18" shingles, and 4d (1 1/2") for 24" shingles. In all cases, fasteners should be long enough to penetrate at least 1" or through the sheathing. Drive them flush, but not so that the head crushes the wood.

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 8 inches from the centerline each way.

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 shingles 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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