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Division B - Standards

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Standard for Cedar Shake and Shingle Roof Systems

How to use this Standard

The fourteen (14) Parts of this Standard contain the requirements, guiding principles, recommendations, and reference materials, necessary to design and construct a project that will qualify for a RoofStar 5-Year Guarantee, RoofStar 10-Year Guarantee, or RoofStar 15-Year Guarantee. Guarantee requirements for a RoofStar 15-Year Guarantee are identified in various Parts. All RoofStar 15-Year Guarantee requirements must be read together with the general requirements for each Part in this Standard.

Readers are advised to review relevant materials that can be accessed through the hyperlinks embedded in the body of text. Part titles shown in blue indicate hyperlinks to more relevant material that the reader is advised to consult.

Refer to Structure and Organization of RPM and Standards in Division A of this Manual for more information about this Standard.

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© RCABC 2024
No reproduction of this Standard, in whole or in part, is lawful without the expressed permission of the RCABC.

1 Materials

See Cedar Shakes & Shingles for RoofStar-accepted cedar products.

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2 Cedar Shingle Roofing (STR-CS)

2.1 GENERAL

This specification is intended to meet or exceed the requirements of the BC Building Code.

Guarantee

A five (5) or ten (10) year RoofStar Guarantee is available on cedar shingle roofing.

2.2 MATERIALS

• Shingles shall be No. 1 Grade (only) conforming to CSA 0118.1-97 Cedar Shakes and Shingles (latest revision) and not less than 405 mm (16") long, and not less than 75 mm (3") but not more than 350 mm (14") wide, per Building Code requirement.
• Flashings shall be 0.56 mm (26 gauge) galvanized iron or 0.80 mm (0.032") aluminum.
• Underlayment shall be one ply No. 15 (asphalt saturated) roofing felt conforming to CSA A123-3-M1979.

2.3 APPLICATION

2.3.1 Deck (Roof Sheathing) Requirements

Red cedar shingles may be applied over spaced sheathing or solid sheathing. When spaced sheathing is used, 19 mm x 89 mm (1" x 4") boards shall be spaced on centres equal to the weather exposure at which the shingles are laid.

Roof Pitch and Exposure

Proper weather exposure is important and depends largely on roof pitch. On roof slopes of 1:3 (4" in 12") or steeper, the standard exposures are 125 mm (5") for 400 mm (16") shingles, 140 mm (5-1/2") for 455 mm (18") shingles and 190 mm (7-1/2") for 610 mm (24") shingles. On roof slopes less than 1:3 (4" in 12") to a minimum of 1:4 (3" in 12"), exposures shall be as follows: 95 mm (3-3/4") for 405 mm (16") shingles, 105 mm (4-1/4") for 455 mm (18") shingles and 145 mm (5-3/4") for 610 mm (24") shingles.

2.3.2 Eave Protection and Underlay

• Underlayment shall be minimum No. 15 perforated asphalt-saturated felt conforming to CSA A123.3 M 1979 and / or ASTM D226-95. Fasten one ply No.15 Felt to deck with sufficient nails to hold in place until shingling. Side laps a minimum 50 mm (2") and end laps a minimum 150 mm (6").

• If required by Building Code, eave protection must consist of a minimum of self-adhesive, rubberized asphalt sheet material 2.2 kg / m² (No. 50) Type S smooth surface roll roofing or two plies of No. 15 asphalt felt lapped 485 mm (19") and cemented together with lap cement, extending from the edge of the roof a minimum distance of 915 mm (36") up the roof to a point not less than 300 mm (12") inside the inner face of the exterior wall. If a gutter is present, the eave protection shall extend a minimum of 40 mm (1-1/2") behind the gutter.

Note: Polyethylene eave protection is not permitted.

2.3.3 Shingles

• Shingles normally are applied in straight, single courses. But application may be varied to achieve certain effects (thatch, serrated, weave and ocean wave applications are common styles). The following applies regardless: shingles must be tripled at all eaves, and butts of first-course shingles should project 40 mm (1-1/2") beyond the roof edge or far enough to ensure proper spillage into gutter. Maximum recommended exposures must not be exceeded. Spacing between adjacent shingles (joints) shall be 6 mm (1/4") nominal. Joints in any one course shall be separated not less than 40 mm (1-1/2") from joints in adjacent courses, and in any three courses no two joints should be in direct alignment.

• Shingles shall project a minimum of 20 mm (3/4") at gable ends.

2.3.4 Valleys

• Metal valley sheets shall be centre-crimped, 600 mm (24") minimum width and, for maximum life, galvanized flashings shall be painted both sides with a good grade of metal paint and underlaid with a strip of No. 15 (minimum) roofing felt. Metal gauges to RoofStar Guarantee Standards.

• Shingles extending into the valley should be sawn to proper mitre. No joints shall be broken into valleys, nor shingles laid with grain parallel to centre line of valley.

2.3.5 Vertical Upstand Flashing

Vertical Upstand Flashing must be installed at all vertical intersections. When fasteners are required to secure exposed metal counter flashings only cladding screws, minimum No. 8 (¹⁄₈") with a rubber gasket grommet or washer, made of metal compatible and corresponding in colour to the metal flashing material are acceptable. Nails are not acceptable as exposed fasteners to secure metal counter flashings.

Materials used must conform to RoofStar Guarantee Standards for Metal.

Apron flashing shall extend a minimum 125 mm (5") up vertical surfaces, 100 mm (4") over the roof material and 100 mm (4") beyond the corners.

Step flashing shall extend a minimum 125 mm (5") up vertical surfaces, 100 mm (4") between courses of roofing and have a 75 mm (3") headlap. Step flashing shall extend a minimum 75 mm (3") beyond the down slope corners and be folded, but not cut.

Water diverter flashing shall be installed at all roof eaves to direct water away from walls and into drainage systems. Diverters shall extend a minimum 125 mm (5") up vertical surfaces, 100 mm (4") over roof material and be installed on a 20-degree angle to the vertical slope.

Backpan flashing shall extend a minimum 150 mm (6") up vertical surfaces, 450 mm (18") up the slope and 100 mm (4") beyond the corners. Corners must be folded, but not cut. If the upstand is more than 750 mm (30") wide, a saddle is recommended. In lieu of a saddle, a backpan that extends a minimum of one-sixth the width of the upstand but not less than 150 mm (6") vertically and up the roof slope to a point equal in height but not less than 450 mm (18") must be used. Counter flashing must be used to shed water from vertical surfaces to the flashings.

Plastic vents or vent flashing shall have a minimum 75 mm (3") flange for the roof material on the upslope side and a minimum 50 mm (2") flange for the roof material on all other sides. Plastic vents or vent flashing shall not be used for combustion or grease laden venting. Acceptable plastic vents or vent flashing must conform to CSA-A93-M82 (R1992), or ICBO #4159.

Metal vents or vent flashing shall have a minimum 100 mm (4") flange for the roof material on all sides and a minimum vertical sealed height of 75 mm (3"). All seams must be fully soldered or welded. Material used must conform to RoofStar Guarantee Standards for Metal.

Plumbing vent flashings shall have a minimum 100 mm (4") flange on all sides and be properly sized for the pipe. The flashing must allow for thermal movement of the vent pipe. Settle caps or storm collars must be used where possible. Acceptable plumbing vent flashings must conform to CSA B272-93.

2.3.6 Hips and Ridges

• A strip of No. 15 roofing felt shall be applied at hips and ridges prior to capping.

• All hips and ridges shall be of the alternate overlap type with concealed nailing. Either site-made or factory-assembled hip and ridge units may be used. Hip and ridge capping must be manufactured from products and grades which conform to CSA 0118.1 and Building Code requirements. Weather exposure should be the same as the field of the roof. Nails must be longer than those used in the field of the roof and of sufficient length to penetrate the underlying sheathing a minimum of 20 mm (3/4") or, in the case of plywood, completely through the sheathing.

• Shakes / Shingles used to manufacture hip and ridge capping shall be fastened (joined) together with a minimum on one corrosion resistant nail (hot dipped zinc, aluminium, or stainless steel, type 304 or 316). Placed approximately 37 mm (1-1/2") from the butt end or alternatively fasten with four nails per cap in a staggered pattern.

• Staples or T nails are not acceptable as the only securement method for the manufacture of hip and ridge capping.

2.3.7 Ventilation - Attic Space / Cathedral / Insulated Roof Assemblies

The attic or ceiling space must be adequately ventilated according to appropriate provincial or local Building Code standards. The design and selection of the ventilation system is the responsibility of the design authority.

Cathedral ceiling and / or insulated roof assemblies must have a minimum space for unobstructed air movement of 63 mm (2.5"), between the roof sheathing and the insulation where joist spaces are not individually vented, the spaces must be cross-strapped with purlins that are not less that 38 mm (1 ½") x 38 mm (1 ½") installed on top of the roof joists.

Note: The B.C. Building Code Part 9 for Housing and Small Buildings, Section 9.19 Roof Spaces, 9.19.1.3 Clearances requires:

(1) Not less than 63 mm (2.5") of space shall be provided between the top of the insulation and the underside of the roof sheathing.

(2) Ceiling insulation shall be installed in a manner that will not restrict a free flow of air through roof vents or through any portion of the attic or roof space.

Cedar shingles applied over insulation and shingles applied to sheathing over insulation without the appropriate air space are not permitted for this application in the RoofStar Guarantee Program.

2.3.8 Nailing Requirement

• Each shingle shall be secured with two only 14-gauge corrosion resistant nails (hot-dipped zinc, aluminum or stainless steel, Type 304 or 316) placed approximately 20 mm (3/4") from each edge and approximately 38 mm (1-1/2") above the butt line of the following course. Nails shall be of sufficient length to penetrate the underlying sheathing a minimum of 20 mm (3/4") or, in the case of plywood, completely through the sheathing. Nail heads shall be driven flush and tight but not so the nail head crushes the wood. Specially marked power nailers utilizing hot-dipped galvanized (or stainless steel for treated shingles) D-Type head nails may be used. Power staplers and staples or T-nails are not permitted.

• The only acceptable nails for use with pressure treated preservative or fire retardant shingles are stainless steel nails (Type 304 or 316) or hot dip zinc-coated steel nails conforming to CSA B111. Stainless steel nails are manufactured by National Nail Inc. and may be obtained through selected RCABC Associate Members.

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3 Cedar Shake Roofing (STR-HS)

3.1 GENERAL

This specification is intended to meet or exceed the requirements of the BC Building Code.

Guarantee

A five (5) or ten (10) year RoofStar Guarantee is available on cedar shake roofing.

3.2 MATERIALS

• Red cedar shakes shall be premium or No.1 Grade of straight-split, taper-split, hand-split and resawn or taper-sawn conforming to CSA 0118.1 except that shakes shall be 100% edge grain. No flat grain is acceptable. Shakes shall be not less than 455 mm (18") long and not less than 100 mm (4") nor more than 350 mm (14") wide with a butt thickness of not more than 32 mm (1-1/4") and not less than 9 mm (3/8" nominal).

• Flashings shall be 0.56 mm (26 gauge) galvanized iron or 0.80 mm (0.032") aluminum.

3.3 APPLICATION

3.3.1 Deck (Sheathing) Requirements

• Red cedar shakes may be applied over spaced sheathing or solid sheathing. When spaced sheathing is used, minimum 19 mm x 89 mm (1" x 4") boards shall be spaced on centres equal to the weather exposure at which the shakes are laid but never more than 190 mm (7-1/2") for 455 mm (18") shakes nor more than 250 mm (10") for 610 mm (24") shakes.

Note: If 24" shakes are used, 19 mm x 140 mm (1" x 6") boards are mandatory.

Roof Pitch and Exposure

• The minimum allowable roof pitch for shakes is 1:3 (4" in 12"). Proper weather exposure is important and shall be limited to the following maximum exposures for a 2-ply roof: 190 mm (7-1/2") for 450 mm (18") shakes and 250 mm (10") for 600 mm (24") shakes.

• For a 3-ply roof the maximum exposures are 140 mm (5-1/2") for 450 mm (18") shakes and 190 mm (7-1/2") for 610 mm (24") shakes.

3.3.2 Eave Protection and Underlay

If required by Building Code, eave protection must consist of a minimum of self-adhesive rubberized asphalt sheet material, 2.2 kg / sq. m (No.50) Type S smooth surface roll roofing or two plies of No.15 asphalt felt lapped 485 mm (19") and cemented together with lap cement, extending from the edge of the roof a minimum distance of 915 mm (36") up the roof to a point not less than 300 mm (12") inside the inner face of the exterior wall. If a gutter is present the eave protection shall extend a minimum of 40 mm (1-1/2") behind the gutter.

3.3.3 Shakes

The beginning or starter course shall be doubled or tripled and butts shall project far enough beyond the roof edge to ensure proper spillage into gutter.

The bottom course may be either 455 mm (18") shakes or cedar shingles No.1 grade or better. Straight-split shakes shall have a tapered starter course (cedar shingles).

After applying each course of shakes, a 455 mm (18") wide strip of No.15 asphalt felt shall be laid over the top portion of the shakes extending onto the sheathing. The bottom edge of the felt shall be positioned at a distance equal to twice the weather exposure above the butt (Note: If open sheathing is used ensure that the top edge of the felt is laying on and secured to the strapping). For example 610 mm (24") shakes laid with 250 mm (10") exposure would have the felt applied 500 mm (20") above the shake butts; thus the felts will cover approximately 100 mm (4") of the top of the shake and extend approximately 355 mm (14") onto the sheathing. When straight-split shakes are used, the “Froe-end” (the end from which the shakes have been split and which is smoother) shall be laid upper most, i.e. toward the ridge. Joints in adjacent courses shall be broken or off-set not less than 40 mm (1-1/2"), and when laid in a 3-ply application, in any three courses no two joints should be in direct alignment. Individual shakes shall be spaced 10 mm (3/8") to 16 mm (5/8") apart to allow for possible expansion. Shakes shall project a minimum of 20 mm (3/4") at gable ends.

3.3.4 Valleys

• Metal valley sheets shall be centre-crimped, 610 mm (24") minimum width and, for maximum life, galvanized flashings shall be painted both sides with a good grade of metal paint and underlaid with a strip of minimum No.15 roofing felt. Metal gauges to RoofStar Guarantee Standards.

• Shakes extending into the valley should be sawn to the proper mitre. No joints shall be broken into valleys nor shakes laid with grain parallel to centre line of valley.

3.3.5 Vertical Upstand Flashing

Vertical Upstand Flashing must be installed at all vertical intersections. When fasteners are required to secure exposed metal counter flashings only cladding screws, minimum No. 8 (¹⁄₈") with a rubber gasket grommet or washer, made of metal compatible and corresponding in colour to the metal flashing material are acceptable. Nails are not acceptable as exposed fasteners to secure metal counter flashings.

Materials used must conform to RoofStar Guarantee Standards for Metal.

Apron flashing shall extend a minimum 125 mm (5") up vertical surfaces, 100 mm (4") over the roof material and 100 mm (4") around the corners.

Step flashing shall extend a minimum 125 mm (5") up vertical surfaces above the finished roof surface, 100 mm (4") between courses of roofing and have a 75 mm (3") headlap. Step flashing shall extend a minimum 75 mm (3") beyond the down slope corners and be folded, but not cut.

Water diverter flashing shall be installed at all roof eaves to direct water away from walls and into drainage systems. Diverters shall extend a minimum 125 mm (5") up vertical surfaces, 100 mm (4") over roof material and be installed on a 20-degree angle to the vertical slope.

Backpan flashing shall extend a minimum 150 mm (6") up vertical surfaces, 450 mm (18") up the slope and 100 mm (4") beyond the corners. Corners must be folded, but not cut. If the upstand is more than 750 mm (30") wide, a saddle is recommended. In lieu of a saddle, a backpan that extends a minimum of one-sixth the width of the upstand but not less than 150 mm (6") vertically and up the roof slope to a point equal in height but not less than 450 mm (18") must be used.

Counter flashing must be used to shed water from vertical surfaces to the flashings.

Metal vents or vent flashing shall have a minimum 100 mm (4") flange for the roof material on all sides and a minimum vertical sealed height of 75 mm (3"). All seams must be fully soldered or welded. Material used must conform to RoofStar Guarantee Standards for Metal.

Plastic vents or vent flashing shall have a minimum 75 mm (3") flange for the roof material on the upslope side and a minimum 50 mm (2") flange for the roof material on all other sides. Plastic vents or vent flashing shall not be used for combustion or grease laden venting. Acceptable plastic vents or vent flashing must conform to CSA-A93-M82 (R1992), or ICBO #4159.

Plumbing vent flashings shall have a minimum 100 mm (4") flange on all sides and be properly sized for the pipe. The flashing must allow for thermal movement of the vent pipe. Settle caps or storm collars must be used where possible. Acceptable plumbing vent flashings must conform to CSA B272-93.

3.3.6 Hips and Ridges

• A strip of No. 15 roofing felt shall be applied at hips and ridges prior to capping.

• All hips and ridges shall be of the alternate overlap type and at same weather exposures as the field of the roof. Either site-made or factory-assembled hip and ridge units may be used.

• Hip and ridge capping must be manufactured from the same grade product (100% edge grain) as used in the field of the roof. Nails must be longer than those used in the field of the roof and of sufficient length to penetrate the underlying sheathing a minimum of 20 mm (3/4") or, in the case of plywood, completely through the sheathing.

• Shakes / Shingles used to manufacture hip and ridge capping shall be fastened (joined) together with a minimum of one corrosion resistant nail (hot dipped zinc aluminium or stainless steel, type 304 or 316) placed approximately 75 mm (1 ½") from the butt end or alternatively fasten with four nails per cap in a staggered pattern.

• Staples or T nails are not acceptable as the only securement method for the manufacture of hip and ridge capping.

3.3.7 Ventilation - Attic Space / Cathedral / Insulated Roof Assemblies

The attic or ceiling space must be adequately ventilated according to appropriate provincial or local Building Code standards. The design and selection of the ventilation system is the responsibility of the design authority.

Cathedral ceiling and / or insulated roof assemblies must have a minimum space for unobstructed air movement of 63 mm (2.5"), between the roof sheathing and the insulation where joist spaces are not individually vented, the spaces must be cross-strapped with purlins that are not less that 38 mm (1 ½") x 38 mm (1 ½") installed on top of the roof joists.

Note: The B.C. Building Code Part 9 for Housing and Small Buildings, Section 9.19 Roof Spaces, 9.19.1.3 Clearances requires:

(1) Not less than 63 mm (2.5") of space shall be provided between the top of the insulation and the underside of the roof sheathing.

(2) Ceiling insulation shall be installed in a manner that will not restrict a free flow of air through roof vents or through any portion of the attic or roof space.

Cedar Shakes applied over insulation and shakes applied to sheathing over insulation without the appropriate air space are not permitted for this application in the RoofStar Guarantee Program.

3.3.8 Nailing Requirement

• Each shake shall be secured with two only 14-gauge corrosion resistant nails (hot-dipped zinc, aluminum or stainless steel, Type 304 or 316) placed approximately 20 mm (3/4") from each edge and approximately 40 mm (1-1/2") above the butt line of the following course. Nails shall be of sufficient length to penetrate the underlying sheathing a minimum of 20 mm (3/4") or, in the case of plywood, completely through the sheathing. Nail heads shall be driven flush and tight but not so the nail head crushes the wood.

• The only acceptable nails for use with pressure treated, preservative, or fire retardant shakes are stainless steel nails (Type 304 or 316) or hot dip zinc-coated steel nails conforming to CSA B111. Stainless steel nails are manufactured by National Nail Inc. and may be obtained through selected RCABC Associate Members.

• Specially marked power nailers utilizing hot-dipped galvanized (or stainless steel for treated shakes) D Type head nails may be used. Power staplers and staples or T nails are not permitted.

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NOTE: Cedar wall applications are specifically excluded from the RoofStar Guarantee Program, and are included below simply as reference to the Reader

4 Cedar Shingle Sidewalls (STR-CS)

Sidewall applications are not applicable for the RoofStar Guarantee Program; this specification is included for your information only.

4.1 GENERAL

There are two basic methods of shingle sidewall application, single-coursing and double-coursing. In single-coursing, shingles are applied much the same as in roof construction, but greater weather exposures are permitted. Maximum exposure for single-coursing No.1 Grade shingles shall be 190 mm (7-1/2") for 405 mm (16") shingles, 215 mm (8-1/2") for 455 mm (18") shingles and 290 mm (11-1/2") for 610 mm (24") shingles. When single-coursed, a shingle wall shall be double layered at the foundation line (single underlay). Double-coursing allows for the application of shingles at extended weather exposure when applied over undercoursing grade shingles. Double-coursing gives a deep, bold shadow line. Maximum exposure for double-coursing No.1 Grade shingles shall be 305 mm (12") for 405 mm (16") shingles, 355 mm (14") for 455 mm (18") shingles and 405 mm (16") for 610 mm (24") shingles. When double-coursed, a shingle wall shall be triple-layered at the foundation line (double underlay).

Exposures for No.2 Grade shingles shall be reduced 50 mm (2") for 16" shingles, and 50 mm (2") for 18" shingles.

4.2 MATERIALS

Shingles shall be No. 1 Blue Label or No. 2 Red Label grade.

4.3 APPLICATION

4.3.1 Special Nailing Requirement

Single-coursed application features concealed nailing with two only box nails of sufficient length to penetrate the sheathing a minimum of 20 mm (3/4") driven approximately 25 mm (1") above the butt line of the following course and approximately 20 mm (3/4") from each edge. For double-coursed application each outer course shingle shall be secured with at least two small-headed nails driven approximately 50 mm (2") above the butt line and approximately 20 mm (3/4") from each side. With shingles wider than 200 mm (8"), two additional nails approximately 25 mm (1") apart shall be placed across the face of the shingle at the same distance above the butt line. Nail heads shall be driven flush and tight but not so the head crushes the wood.

4.3.2 Corners

Outside corners shall be constructed with an alternate overlap of shingles between successive courses. Inside corners shall be mitred over a metal flashing or may be made by nailing a S4S 38 mm (1-1/2") square strip in the corner over a metal flashing after the shingles of each course are butted to the square strip.

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5 Cedar Shake Sidewalls (STR-HS)

Sidewall applications are not applicable for the RoofStar Guarantee Program, this specification is included for your information only.

5.1 GENERAL

• Maximum recommended weather exposure for single-coursed wall construction is 215 mm (8-1/2") for 455 mm (18") shakes and 290 mm (11-1/2") for 610 mm (24") shakes. Nailing shall be concealed with nailing points 25 mm (1") above the butt line of the course to follow.

• Double-coursed application requires an underlay of shakes or cedar shingles. Weather exposures up to 355 mm (14") are permissible with 455 mm (18") resawn shakes and up to 500 mm (20") with 610 mm (24") resawn or taper-split shakes. If straight-split shakes are used, the double-coursed exposure may be 405 mm (16") with 455 mm (18") shakes and 560 mm (22") for 610 mm (24") shakes. For double-coursed application each other course shake shall be secured with at least two small-headed nails driven approximately 50 mm (2") above the butt line and approximately 19 mm (3/4") from each side. With shakes wider than 200 mm (8"), two additional nails, approximately 25 mm (1") apart, shall be placed across the face of the shingle at the same distance above the butt line. Nail heads shall be driven flush and tight but not so the head crushes the wood.

5.2 MATERIALS

See material requirements for STR-HS (Cedar Shake Roofing).

5.3 APPLICATION

5.3.1 Corners

Outside corners shall be constructed with an alternate overlap of shakes between successive courses. Inside corers shall be mitred over a metal flashing or may be made by nailing a S4S 38 mm (1-1/2") square strip in the corner over a metal flashing after the shakes of each course are butted to the square strip.

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