Application Handbook
Product Description W estern Red Cedar is scientifically classified as a “Durable” species in the United Kingdom and because of this durability it is widely favoured by architects and engineers seeking an aesthetically pleasing, light weight alternative to traditional roof and wall tiles. For over a century Western Red Cedar Shakes and Shingles have proven to be a superior material for roof and wall cladding which is durable, warm and resisitant to extremes of wind and weather.
Shakes 1. Hand split and Resawn Shakes Cedar blocks of appropriate length are split by a hydraulically powered knife, called a cuber, into straight boards, or blanks. Then the blank is fed into a bandsaw, which saws the blank from corner to corner, producing 2 tapered shakes, each with a natural split face and sawn back. Shakes are produced in 2 lengths, 455mm and 610mm, and 2 grades, Number 1, which allows 20% flat grain content, and Premium Grade, which is 100% vertical grain.
GENERAL ROOF DESIGN DETAILS Battens Shingles shall be applied over softwood lumber battens of 25 x 38mm minimum dimension over rafter minimum dimension of 75 x 38mm, with maximum rafter centres of 600mm. Larger battens of 25 x 50mm are required for 100 x 51mm rafters with rafter spacing of up to 812mm (Figure 1). Shakes require minimum batten dimension of 19 x 50mm. Wider battens are recommended for alpine regions where snow load is a factor.
Shakes In shake application, battens of 25 x 50mm minimum are spaced on centres equal to the weather exposure (Table 4, page 16) at which the shakes are to be laid, measured from 38mm past the fascia board. Maximum weather exposure for 455mm shakes is 190mm, and for 610mm shakes is 255 mm. Breathable membrane interlay at the eave and between the shake courses is required whether battens or solid sheathing is used.
MANSARD ROOF DETAILS The mansard is particularly well suited to renovation work on pitched roof houses because the upper story can be enlarged without adding extra height to the structure. The conversion of a pitched roof bungalow to a mansard provides a floor area on the upper floor that can be identical to the main floor area. The low downward slope of the mansard roof line acts visually to reduce the scale of a building and helps to eliminate a boxy appearance.
LOW SLOPE ROOF DETAILS The minimum roof slope on which shakes and shingles are recommended is 19 degrees. It is possible, however, to apply shingles or shakes successfully to solid sheathed roofs of lower slope providing a special method of application is followed (Figure 7).
ROOF JUNCTURE DETAILS Correct construction of roof junctures is vital to ensure weathertightness. In the following cases, where metal flashing is employed, it should be no less than 26 gauge galvanized steel (or acceptable equivalent). It should be painted on both sides with a good metal or bituminous paint. Flashing materials should be painted after bending to maintain the integrity of the coating.
ROOF VALLEY FLASHING DETAILS Most roof leaks can occur where water is channelled off the roof or where the roof abuts a vertical wall or chimney. At these points, metal valleys and flashings are used to assist the shingles or shakes in keeping the structure sound and dry. Structural members that protrude through a roof should also be flashed at all intersecting angles to prevent leakage.
ROOF PROJECTION FLASHING DETAILS Recommend construction details for applying metal flashings around typical roof projections such as chimneys and vent pipes (Figure 13). For roofs and walls, the use of stainless steel, phosphor, or silicone bronze nails is recommended. Standard shingle nails are 31mm x 1.8mm stainless steel annular ring shanked. Standard shake nails are 50mm x 2mm stainless steel annular ring shanked. Nails shall be driven flush but not so that the nail head crushes the wood.
VENTILATION DETAILS The importance of good attic ventilation beneath the roof cannot be over-emphasized. Such movement of air will prevent or inhibit condensation of moisture on the undersurface of the shingles or shakes, or on the roof decks. Vents should be provided at the soffits (eaves) as well as at gable ends (screened to prevent ingress of insects), with cross-ventilation desirable.
SPECIALTY ROOF DECK DETAILS Wood Deck Wood decks form an ideal base over which to apply cedar shingles or shakes, since they can be attached in the conventional manner. Where a layer of insulation, normally one of the rigid types, is to be included, the problem of how to fasten shingles or shakes is created.
Cedar shingles or shakes (applied as per specification) Exterior panels Rigid insulation Vapor barrier (if required) Wooden deck Joist Fig.
COLD WEATHER ROOF SYSTEM DETAILS Western Red Cedar shingles and shakes are an excellent roofing material for cold weather areas that experience heavy snowfall and severe temperature extremes. A natural wood product, they offer the advantages of durability, superior wind resistance, and good thermal and acoustical properties. As with any other roofing material, however, their best performance depends upon proper design, sound construction practice, and correct installation.
Wide overhangs at the eaves should be avoided as they provide large cold areas for snow and ice build-up. A strip of metal along the eaves helps shed ice quickly. Sliding ice and snow are constant hazards and should be given primary consideration in the total building design. Outside doors should not be located at the bottom of a roof slope. Entrances and all pedestrian traffic areas are better situated beneath the gable ends of the roof.
GENERAL WALL DESIGN DETAILS Cedar shakes and shingles’ beautiful appearance, superior insulative value, adaptability to diverse design forms, and low maintenance make them the Natural Choice for exterior and interior wall applications. Exterior Walls Prepare the walls by removing or pounding nails or protruding objects flush. Solid sheathing or spaced battens are recommended for wall installation.
Designer (Fancy Butt) Shingles Many interesting and pleasing design alternatives can be achieved with the use of Designer Shingles. Butt profiles of square, round, arrow, fish scale, half cove, diamond, diagonal, hexagonal, and octagonal can be combined to accommodate imaginative profiles.
Coverage and Exposure Tables 1 Square = 9.2 square metres or 100 square feet Shingle Coverage Table 1 Approximate coverage of one square (4 bundles) of shingles based on following weather exposures LENGTH AND THICKNESS 90mm 100mm 115mm 125mm 140mm 150mm 165mm 180mm 190mm 405mm x 5/50mm 6.7 7.4 8.5 9.3 – – – – – 455mm x 5/55mm – 6.7 7.6 8.3 9.3* – – – – 610mm x 4/50mm – – – – 6.9 7.3 8.1 8.8 9.3* NOTE. *Maximum exposure recommended to roofs.
Weights Table Installed Weights Shingles kg/m2 125 gauge 95 gauge Untreated 6.14 8.09 Preservative treated 12.28 16.09 Fire retardant treated 7.02 9.25 250 gauge 190 gauge 7.1 9.35 Preservative treated 10.93 14.39 Fire retardant treated 8.2 10.
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