ARCHIVED - RoofStar Guarantee Standards for ASM Roof Assemblies

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ARCHIVED - RoofStar Guarantee Standards for ASM Roof Assemblies

How to use the Guarantee Standards section

This section contains the Standards, Guiding Principles, Recommendations and reference materials necessary for the design and installation of a roof qualifying for a RoofStar Guarantee.

All relevant Standards for the selection and application of materials necessary to qualify for a RoofStar Guarantee are found in this section. Readers are advised to review relevant materials that can be accessed through the links available in the body of text or embedded in section titles; these are shown in blue font. Subsection titles shown in blue indicate links to more relevant material that the reader is advised to consult.

Content in this section is colour-coded according to four classes:

Guarantee Standards
Guiding Principles
Reference materials

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Compliance with RoofStar Guarantee Standards is mandatory for issuance of the RoofStar Guarantee certificate. The RoofStar Guarantee Program covers only architectural metal roof systems applied over solid decking. Structural metal roof systems requiring metal panels to span framing members unsupported by solid decking are not covered under the RoofStar Guarantee Program.

Note: Repairs or renovations to existing roof systems do not qualify for an RoofStar Guarantee.

1.1 Roof Slopes

.1 A minimum slope of 1:6 (2" in 12") is required. Non-conforming (i.e. curved) applications will be considered if design and installation details are submitted in writing to the Technical Manager of the RoofStar Guarantee Program prior to the tendering of documents.

.2 Architectural metal roof panels that are installed on curved roof decks must be roll-formed to the curvature of the decks by use of a panel-curving machine, specifically designed for the purpose. Alternatively, if flat roll formed metal panels are installed on curved roof decks a panel stress calculation must be completed by a professional engineer prior to installation of metal panels.

.3 If proprietary systems are specified, the manufacturer's suggested minimum slope and application procedures must be followed in addition to RoofStar Guarantee requirements.

.4 For slopes between 1:6 (2" in 12") and up to but not including 1:3 (4" in 12"), a continuous self-adhesive membrane, or torch-weld underlay must be installed prior to the application of the sheet metal roofing. Direct torch application to wood surfaces is not permitted.

.5 For slopes 1:3 (4" in 12") and greater, a RoofStar-accepted underlay for metal roofing is required. Accepted materials for this purpose are listed in the Eave Protection & Underlayment (Architectural Metal Roofing) section of this Manual.

1.2 Tie-in (Re-roofing or Building Additions)

Where a new roof is tied-in to an existing roof, the two areas must be isolated and separated by a curb joint properly constructed a minimum height of 125 mm (5”), attached to the structure and properly flashed. If job conditions or aesthetic considerations do not allow for a curb joint, written permission must be obtained from the RoofStar Guarantee Program (Technical Manager) to eliminate curb joints; a positive water cut-off must be installed to the deck to isolate the existing roof from the new roof.

1.3 Roof Decks

1.3.1 Wood Decks

.1 All wood decks shall be properly nailed and cracks shall be covered with metal prior to acceptance of deck surface. This work is to be done by others.

.2 Plywood is the only acceptable sheathing to be used for wood roof decking and shall conform to the minimum requirements of the BC Building Code and be a minimum thickness of 12.5 mm (½"). Tongue and groove plywood sheathing, a minimum thickness of 15.9 mm (5/8"), is required for decking on all copper and zinc non-ferrous metal panel roof systems.

.3 OSB (sheathing) is not acceptable.

1.3.2 Steel Decks

.1 Steel decks must conform to one of the following specifications: ASTM Standard Specification A653 / A653M, Sheet Steel, Zinc-Coated (Galvanized) by the Hot-Dip Process, Structural (Physical) Quality, minimum Grade 33, with a design thickness of 22 gauge (0.759 mm) or greater and a minimum zinc coating designation Z275.

ASTM Standard Specification A792 / A792M, Steel Sheet, Aluminium-Zinc Alloy-Coated by the Hot-Dip Process, General Requirements, minimum Grade 33, with a design thickness of 22 gauge (0.759 mm) or greater and a minimum aluminium-zinc alloy coating designation AZ150.

1.3.3 Concrete Decks or Walls

.1 Direct contact between metal roofing and concrete, light concrete, stone and mortar must be avoided. The selection of a suitable underlay, insulation, and method of attachment to a concrete deck or wall is the responsibility of the design authority.


2.1 Material Acceptance

.1 Materials and metal roofing systems to be covered by the RoofStar Guarantee Program must be listed in the Accepted Materials section of this Manual.

.2 Member contractors must provide a mill certification for all metal roofing projects installed under the RoofStar Guarantee Program. Mill certifications must confirm that the sheet metal used for forming metal panels and flashings conform to or exceed one of the following standards:

Sheet Steel Materials
0.64 mm (0.0252", 24 gauge) galvanized steel sheet, conforming to ASTM A653 / A653M-06 SS Grade 33, Z275 (G90) coating. Thickness tolerance as per ASTM A924 / A924M-06 ±0.08 mm (0.003") for sheet widths not exceeding 1500 mm (60").
0.64 mm (0.0252", 24 gauge) aluminium-zinc alloy coated steel sheet, conforming to ASTM A792 / A792M-06 SS Grade 33, AZM150 (AZ50) coating. Thickness tolerance as per ASTM A924 / A924M-06 ±0.08 mm (0.003") for sheet widths not exceeding 1500 mm (60").
Non-Ferrous Materials
Copper 0.56 mm (.0216" 16 oz) copper sheet, cold rolled roofing copper to ASTM B370-91. Maximum thickness tolerance ± 0.04 mm (0.0015)
Zinc 0.81 mm (0.031") ± 0.03 mm thick zinc sheet conforming to European Standard EN 988-1996. Zinc grade Z1 conforming to En 1179 that is 99.995% minimum zinc content, with addition of copper-titanium alloys. Maximum thickness tolerance variation ± 0.03 mm (0.0012").

.3 Flat stock used for flashing fabrication on metal roofing systems must meet or exceed the grade and design thickness (gauge) of the metal roof panels.

2.2 Material Storage

.1 All materials must be protected from weather by properly stacking above ground or roof surface. Elevate one end and block centre to prevent sagging. Protect panels against condensation between adjacent surfaces. Retain factory packaging or provide other adequate covering until material is applied. Handle panels with non-marring slings and use a spreader bar for hoisting. If site formed panels are specified, coils must be protected from condensation and stacked in an upright manner.

3 UNDERLAYMENT - Eave and Detail Protection

.1 For insulated metal roof systems an RoofStar-accepted underlay must be installed under the insulation. A vapour-permeable membrane overlay may also be used over insulation for additional moisture protection. Note: Modified bituminous membranes that are not arranged under insulation must have a high softening point bitumen with a minimum flow temperature of 87.7°C (190°F) ASTM D5147 high temperature stability.

.2 The preferred installation of the underlay is parallel to the eaves. However, the underlay may be installed perpendicular to the eaves provided the laps are self-sealing or sealed with a suitable lap cement recommended by the underlay manufacturer.

.3 Underlays must be acceptable as a RoofStar-accepted Architectural Sheet Metal Underlay, and meet or exceed the National Building Code of Canada (current edition) for roofing underlayment.

.4 A slip-sheet is recommended over asphaltic underlay under steel metal roof panels. This prevents the metal roofing panel from sticking to the underlay, allowing natural expansion and contraction of the metal roofing panels. Slip-sheets are typically lightweight resin sized or unsaturated building paper weighing 0.3 kg / meters squared (6 lb / square). A slip-sheet is required over asphaltic based underlay for non-ferrous (copper and zinc) based metal roof panels.

.5 Ice and water eave protection is required for all RoofStar Guaranteed metal roofing systems. Eave protection must be an RoofStar-accepted self-adhered modified bituminous membrane. Eave protection must be carried 600 mm (24") min. inside interior walls or 900 mm (36") in heavy snow load conditions.

.6 Valley protection membrane must be 975 mm (39") min. wide and centred on the valley. Membrane to be the same materials as used for eave protection (see 3 above).

.7 Back pan membrane protection must be 900 mm (36") wide. Membrane to be the same materials as used for eave protection (see 3 above).

.8 Vertical upstand (curbs, walls, etc.) membrane protection must extend 100 mm (4") vertically and 150 mm (6") on to the underlayment. Membrane to be the same materials as used for eave protection (see 3 above).

.9 Manufacturers approved proprietary panel underlayments and or insulation overlays must be used with all zinc based standing seam roof systems.

.10 Built in gutter membrane over insulation must transition onto underlayment membrane that is under insulation by use of sloped insulation and as detailed in construction drawing E1.7.16 Built-in Gutter .

.11 Minimum allowable thicknesses for a modified bituminous membrane underlayment is 1mm.


4.1 Intent

Air and vapour barriers, along with thermal barriers, water resistive barriers and water-shedding surfaces, serve to separate the outside environment from the interior environments of a structure. Continuous air barriers are perhaps the most critical. Building Codes in force in each jurisdiction, and the National Energy Code (2011), require the selection and proper installation of “a continuous air barrier system comprised of air-barrier assemblies to control air leakage into and out of the conditioned space” (NEC 2011).

Continuity of the air and/or vapour barrier from the wall systems and roof systems is essential to the satisfactory performance of either or both. Therefore, proper connection between air and/or vapour barrier systems is essential, and the responsibility of both the design authority and trades constructing walls and roofs.

Air barriers control “flow of air through the building enclosure, either inward or outward” (Guide for Designing Energy Efficient Building Enclosures, Homeowner Protection Office). Controlling air flow into and out of conditioned spaces affects the performance of “thermally efficient enclosure assemblies” (ibid), impacts the potential for condensation in between materials, and directly influences rain water penetration of the building envelope. Some air barriers are considered permeable, others air-impermeable or ‘airtight’. The suitability of one over the other, in the application of a roofing system, is left to the discernment of the design authority and/or the roofing contractor. Consequently, the RoofStar Guarantee Program strongly recommends that designers and builders of roof systems intended to qualify for a RoofStar Guarantee carefully consider the regulatory design and installation requirements for effective, continuous air barrier systems.

Vapour barriers regulate or prohibit the movement of water vapour from one space to another by means of diffusion. Consequently, these barriers are referred to as either vapour-permeable or impermeable. Diffusion is a slow process, in contrast to air movement, and its regulation is not always mandatory or even desirable. Consequently, because continuous vapour barriers “are not needed within all climate zones and assemblies”, they are considered non-critical and may be left to the discretion of the design authority. Nevertheless, where continuous vapour barriers are required and specified by provincial or municipal building codes (current and in force), the RoofStar Guarantee Program requires that a suitable vapour barrier system be selected by the design authority and properly installed by the roofing contractor in conformity with the vapour barrier manufacturer’s published instructions, and with the design authority’s specified details.

Any references in this Manual to installation methodologies, and any construction details that show air and/or vapour barriers, are merely illustrative and not prescriptive. Installers of continuous air and/or vapour barrier systems are urged to understand and comply with best practices for their application.

4.2 Limitations and Exclusions

  1. Air and vapour barrier performance is not part of the RoofStar Guarantee, and air/vapour barrier materials are not listed in the Accepted Materials section of this Manual. Therefore, the decision to specify an air and/or vapour barrier, the placement of a continuous air and/or vapour barrier in relation to a roof assembly and system, and the selection of suitable materials for that application, is the sole responsibility of the design authority.The design authority is urged to review and consider the performance characteristics of materials available for such applications.

    Neither the RoofStar Guarantee Program nor the roofing contractor will accept any responsibility for damage to, or failure of, the roof system caused by the use or absence of air and/or vapour barriers.

  2. Proper installation and continuity of air and/or vapour barriers within the roof assembly is the responsibility of the roofing contractor. The air/vapour barrier must:

  • extend past the roof membrane flashing by 100mm (4”) on new construction providing a positive (water-shedding) lap seal union between courses of material for the wall air/vapour barrier membrane applicator.
  • be sealed to the wall air/vapour barrier on roof replacement projects.

Installation must conform to the manufacturer’s published requirements and the design authority’s design details.

4.3 Material Selection

  1. Fully supported air and/or vapour barriers must possess a minimum published static puncture resistance rating of 150 N (34 lbf) (ref. CGSB-37.56-M for both test method and standard limits) and be either self-adhering or torch-applied. For unsupported air and/or vapour barriers, see 4.3.3 below. Therefore, while responsibility for the selection of a suitable air/vapour barrier rests with the design authority, a roof designed and built to qualify for a RoofStar Guarantee shall not include either polyethylene sheet plastic or bitumen-impregnated kraft paper.

  2. Where air and/or vapour barriers are specified by the design authority, they must be selected from the materials listed in the wind-tested assemblies reports for MARS, PARS or AARS roof systems (excluding polyethylene sheet plastic and kraft paper, as noted above). For a complete listing of current wind test reports, click on the linked system acronyms above.

  3. Notwithstanding any of the foregoing, the RoofStar Guarantee Program strongly recommends that any air and/or vapour barrier system be installed over a smooth, continuous plane (for example, concrete or plywood). Consequently, a deck overlay board installed on corrugated steel roof decks in highly recommended. Where no deck overlay board is installed and the air and/or vapour barrier is partially unsupported (for example, on a steel deck), the air and/or vapour barrier must have a published static puncture resistance of at least 400 N (90 lbf). Furthermore, both the side laps and end laps must be fully supported.

  4. Should the air/vapour barrier membrane be used as a temporary roof during project construction by either the roofing contractor or by other trades, a minimum 2mm thick bituminous membrane is recommended.

  5. Because curing concrete releases considerable moisture that can compromise the performance of a roof system, a vapour barrier installed on new concrete decks (28 days or older) must be selected to prevent condensation inside the roof system. A membrane with a permeability of 0.01 perms (Class I) is recommended. Nevertheless, the selection of the vapour barrier product is the responsibility of the design authority.

4.4 Vapour Retarder Design for High-Humidity Building Interiors

Careful consideration should be given to the performance characteristics of air and/or vapour barriers when specifying such a membrane for roof assemblies constructed over high-humidity building interiors. These types of building interiors include (but are not limited to)

  • Swimming pools
  • Commercial laundry facilities
  • Large aquariums

Vapour retarders for high humidity facilities should have a perm rating as close to zero as possible, be durable, multi-layer membranes that are effective in preventing vapour drive into the roof systems from the interior of high humidity environments.

Thin, lightweight, single-layer vapour retarders are prone to damage during installation of roof assemblies and are therefore not recommended for use over high humidity building interiors.

4.5 Ventilation

The attic or ceiling space should be adequately ventilated according to the BC Building Code standards (current edition). The design of roof ventilation is the responsibility of the design authority.


.1 Insulation is to be specified by the design authority. A list of acceptable insulation materials may be found in Roof Deck Insulation.

.2 When panel clips with bearing plates are installed directly over insulation, the compressive strength of the insulation must be a minimum of 138 kPa (20psi) and the maximum thickness of the insulation shall not exceed as specified in the proprietary designed assembly. Drag load fastening must be designed to withstand the anticipated loading. Insulation bearing plates are not permitted for use in high snow load regions unless expressly accepted in writing under the seal of a structural engineer.

.3 Insulation and overlay board joints must be offset or staggered a minimum 300 mm (12") from adjacent layers and rows.


.1 Proprietary fasteners and clips must be listed as acceptable by the roll form machine manufacturer for use with the metal roofing systems and must be corrosion resistant. Shop fabricated, one-piece construction attachment clips for sheet steel metal roofing systems must be a minimum 100 mm (4") in length, have a minimum, deck flange width of 25 mm (1") and be formed to a suitable height that permits the attachment return to engage the male leg of standing seams. Clips must be corrosive resistant, be attached by two screws, and have evenly spaced indents or guide holes for fastener placement.

Attachment clips for steel metal roofing systems must be formed from zinc-coated or aluminium-zinc alloy-coated steel sheet that conforms to ASTM Standards Specifications A653 / A653M, or A792 / A792M, minimum Grade 33 with a design thickness of 22 gauge (0.759 mm) or greater.

.2 Concealed fasteners should be a low profile head (Pancake Head) to provide added clearance for systems requiring hidden attachment.

.3 Concealed fasteners and proprietary fastening systems used to secure metal roofing must comply with the manufacturer’s minimum recommended attachment schedule.

.4 Exposed fasteners used to secure metal flashings must be high domed, gasketed, cladding type screws, and compatible with metal panel material. Colour to match the metal roofing system.

.5 Panel clip bearing plates designed for fastening panel clips directly over insulation must be specified or listed as acceptable, by the metal panel machine manufacturer, for use with the metal roof panel system.

.6 Wood battens / strapping, used to install insulated metal roofing systems, must be pressure-treated with a non-oil wood preservative.


.1 Metal roofing systems must be installed with clips and screws that are specified or listed as acceptable, by the metal panel machine manufacturer, for use with the metal roofing system.

.2 Contractors and owners of metal panel machines are responsible to meet or exceed the panel machine maintenance standards as established by the roll form machine manufacturer.

.3 Sheet steel roof panels may be roll-formed without stiffening ribs. Stiffening ribs are recommended to help reduce oil-canning.

.4 Sheet steel roof panels may be roll-formed to a maximum of 500 mm (20”).

.5 The maximum width permissible for copper and zinc non-ferrous metal roof panels is 425 mm (17″); these may be roll-formed with or without stiffening ribs or striations incorporated into the panels.


8.1 Wind Uplift

The RoofStar Guarantee Program (RCABC Guarantee Corp., or RGC) initiated an investigation to establish the wind uplift resistance of architectural concealed fastener metal roof systems for use in British Columbia. The wind uplift tests were carried out at the Dynamic Roofing Facility at National Research Council, Institute For Research In Construction (NRC / IRC).

NRC / IRC report No.B1040 –3 (see ASM Special Applications) provides a simplified procedure for wind uplift design for roof assemblies with architectural metal roof coverings. In addition, NRC / IRC reports No. B1040-1 and B1040-2 provided the wind resistance test results for RoofStar-accepted metal panel systems and assisted the RoofStar Guarantee Program in developing guarantee standards and acceptance criteria for the Architectural Concealed Fastener Metal Roof Systems that are accepted for used in the RoofStar Guarantee Program.


Built-in gutters (see also Detail E1.7.17) adjoining metal roofing systems are to be installed by RCABC member contractors in order to qualify for an RoofStar five (5) or ten (10) year guarantee.

.1 Membranes acceptable for use in built-in gutters are fully adhered EPDM, SBS, PVC and TPO membranes.

.2 Metal roof panels adjoining a built-in gutter must be fastened a minimum of 100 mm (4") above the maximum water fill level.

.3 Metal roof system underlay / eave protection must overlap built-in gutter membrane by a minimum of 200 mm (8").

.4 Copper sheet with soldered seams and a RoofStar-accepted underlayment is acceptable for use as a built-in gutter liner material on copper standing seam metal roof systems.

.5 Stainless steel sheet with welded seams and a RoofStar-accepted underlayment is acceptable for use as a built-in gutter liner material on zinc and copper standing seam metal roof systems.

.6 Fasteners shall be installed 4” or more above the maximum water line, and gutters must include a scupper overflow drain.


.1 Mansards are considered part of the roof assembly. For applications of metal roofing to mansards follow the same RoofStar Guarantee Standards listed in this Section.


.1 Snowguards are not part of the roof assembly. The decision to use, and / or the selection of snowguards, is the responsibility of the design authority. Neither the RoofStar Guarantee Program nor the roofing contractor will accept any responsibility for damage to, or failure of, the roof system caused by the use or absence of snowguards.

.2 The design authority is advised to consult with the manufacturer and the roofing contractor when building in areas considered by Environment Canada as high snow load areas. (For RoofStar Guarantee purposes, high snow load is considered regional areas with snow loading higher than 3.5 kPa as referenced in the National Building Code Appendix C “Climatic Information for Building Design in Canada”) Consideration should be given to: slope, entrances / exits, penetrations, and the proximity of adjacent structures.

.3 A solid substrate, a minimum slope of 1:1.5 (8"/12"), the use of an Accepted self-adhered modified bituminous membranes as eave protection, and underlay are required (see Accepted Materials).


.1 When required, closures are to be constructed of weatherproof laminated, semi-rigid, cross-linked polyethylene foam, tightly fit to the panel profile.


.1 Caulking shall be non-hardening, suitable for exterior use, high quality butyl or polyurethane sealant in either gun grade or sealant tape form. Two rows of caulking are required for all metal valley and metal flashing overlaps.

.2 Caulking shall conform to any one of the following:

.1 CGSB 19-GP-5M, “Sealing Compound, One Component, Acrylic Base, Solvent Curing”;
.2 CAN / CGSB-19.13, “Sealing Compound, One Component, Elastomeric, Chemical Curing”;
.3 CGSB 19-GP-14M, “Sealing Compound, One Component, Butyl-Polyisobutylene Polymer Base, Solvent Curing”; or
.4 CAN / CGSB-19.24, “Multi-Component, Chemical Curing Sealing Compound”.

Caulking shall be selected for its ability to resist the effects of weathering. Caulking must be compatible with and adhere to the material which it is applied to.


14.1 Weather Stops

.1 Two panel weather stops must be installed at up-slope terminations. Weather stops may be any combination of foam closures, metal Z-closures, metal flashing turned down between panel ribs to close off openings and / or turned up (bread panned) panel ends.

.2 Metal panel ends turned up (bread panned) must be turned up to a height equal to the panel ribs or standing seams. Turned up corners (dog ears) are not to be cut.

.3 Metal Z-closures must be sealed weather tight with caulking and / or sealant tape.

14.2 Metal Valleys

.1 Metal valley overlaps must be a minimum of 200 mm (8") with two rows of approved caulking or sealant tape.

.2 Metal valley drag load fastening (top edge of valley sections) shall be 75 mm (3") o/c. Drag load fastening is mandatory on unhooked valleys but may not be required on hooked valleys.

.3 Valley dividers are required and must be a minimum of 25 mm (1") high.

.4 Exposed valley widths must be a minimum 125 mm (5") from divider to metal roof panel on each side of the divider. Increased width is recommended in heavy snow load areas.

.5 Unhooked metal valley sections must be returned 25 mm (1") and secured with minimum 50 mm (2") wide metal clips, fastened with two fasteners each. Bend metal clips back over fasteners to protect the metal panels. Metal roof panels must overlap unhooked metal valleys a minimum of 275 mm (11") and be sealed with two rows of preformed foam closures adhered with approved sealant tape (see Detail E1.7.6).

.6 Hooked metal valley, metal roof panel overlaps must be a minimum of 125 mm (5") wide with a one-piece built-in hook strip. Fasteners must be 200 mm (8") o/c and covered with approved self-adhered modified bituminous membrane sealed to the valley protection membrane (see Detail E1.7.5).

14.3 Metal Cap / Hip Flashing

Metal cap / hip flashing must extend a minimum of 150 mm (6") over metal roof panels on each side of the ridge / hip.

.1 Standard cap / hip flashing must be hooked to metal Z closures which are set in sealant tape and fastened through the metal roof panel into the deck or fastened to each standing rib with manufacturer-approved, colour matched, high domed gasketed fasteners and preformed foam closures installed as a weather seal (see Detail E1.7.11).

.2 Notched cap / hip flashing must be fastened on each panel rib and preformed foam closures installed as a weather seal. Only manufacturer-approved, colour matched, high domed gasketed fasteners may be used (see Detail E1.7.12).

14.4 Perimeter Edge Securement

.1 Metal panels with low intermediate stiffening ribs must be installed using a perimeter hook strip (see Detail E1.7.3).

.2 Trapezoidal and intermediate rib standing seam metal roof panel perimeter eave securement must be installed according to the manufacturer’s printed instructions and RoofStar Guarantee Standards. Exposed fasteners are not to be used (see Detail E1.7.4).

14.5 Penetrations

.1 Metal roof panel penetrations, e.g. plumbing, venting, flashings, etc., must have a minimum 300 mm (12") clearance from all other roof projections to permit proper flashing.

.2 Metal roof flexible pipe penetration flashings must be located so as not to interfere with standing seams or panel ribs. If interference is unavoidable, roof curbs or a split sheet detail must be used (see Detail E1.7.8 and Detail E1.7.9).

14.6 Low Slope Tie-In

.1 Metal roof panels adjoining a low slope roof must terminate 200 mm (8") up the slope from the roof surfacing.

.2 Metal roof system underlay / eave protection must overlap low slope roof membrane flashing by a minimum of 100 mm (4").

ASM Roof Systems

Accepted Materials