Template:Part 13 (Waterproofing Roofs)

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Template:Part 13 (Waterproofing Roofs)

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1 General

This Part pertains to Linear Metal Flashings (different from penetration flashings), fabricated from sheet metal and designed to divert water away from the membrane flashing termination, usually onto the roof. Linear Metal Flashings also protect the membrane from weathering and damage, provides an aesthetic finish to the roof assembly. Linear Metal Flashings are not a waterproofing component. Consequently, the roofing membrane should be continuous beneath the metal (see membrane flashing requirements under Part 10 PERIMETERS and WALLS and Part 11 DRAINS and PENETRATIONS).

Linear Metal Flashings include, without limitation,

  • Coping (cap) flashing.
  • Counter-flashing.
  • Base flashing.
  • Fascia flashing.
  • Perimeter edge flashing (similar to a “gravel stop” flashing).

For further details, the Sheet Metal and Air Conditioning Contractors National Association, Inc. (SMACNA) publishes a reliable reference for the proper design and installation of architectural sheet metal.

1.1 Definitions

Refer to the Glossary for further definitions of key terms used in this Manual.

1.2 Design

1.2.1 RoofStar 15-Year Guarantee

  1. Only metal flashings fabricated from 24-guage stock (or thicker) qualify for a RoofStar 15-Year Guarantee.

1.2.2 All Projects

  1. Linear Metal Flashings described in any Part of this Standard are considered necessary and integral to the scope of a Project designed and constructed to qualify for a RoofStar Guarantee. Furthermore, only new Linear Metal Flashings may be specified and installed; reuse of any existing Linear Metal Flashings is prohibited and may void the Guarantee. See also 1.6 RoofStar Guarantee: Coverage and Limitations.
  2. Subject to the requirements in this Standard, the Design Authority must specify
    1. metal type, finish and gauge.
    2. seam types.
    3. length of flashings (if different from the Guarantee Standards outlined below)
    4. method of attachment (concealed or exposed fasteners).
  3. Design drawings must detail metal flashing profiles desired for the Project; keep metal flashings away from the water plane or standing water by at least 25 mm (1”).
  4. Membranes that are UV-sensitive must be protected with Linear Metal Flashings but they are not required when the membrane is continuously sealed and otherwise protected from UV radiation (as, for example, sleepers enveloped with a UV-resistant or granule-surfaced membrane).
  5. All exposed membrane edges must be protected with metal flashings or a 2-part reinforced liquid flashing (in conformity with 11.3.3.3 Liquid Membrane Flashing).
  6. Notwithstanding the foregoing, the Design Authority may specify metal flashings to cover parapet caps, sleepers or curbs
    1. for aesthetic reasons.
    2. to protect the membrane from damage resulting from maintenance, pressure washing of decks or pavers, or foot traffic.
  7. When the top surface of a wall exceeds 100 mm (4") in width, it must be sloped to promote drainage; slope the top surface at least 2% toward the roof. Drainage toward the exterior of a building is not recommended.
  8. All metal cap (coping) flashings must be fully supported.
  9. As length and breadth of metal cap (coping) flashings increases, it is necessary to adjust the gauge and length of flashing segments to counteract anticipated distortions. Each type of metal will behave differently. The following standards apply to the use of pre-finished galvanized steel (the most commonly used material for metal flashings) when stiffeners or cross-breaking are not used to counter-act oil canning. The Design Authority must specify slope, gauge and length using the standards in the table below:
    Table 13.1 Pre-finished Galvanized Steel Cap (Coping) Flashing (Gauge and Length Standards)
    Horizontal Span Minimum
    Slope
    Gauge Maximum Flashing
    Segment Length
    Seam Options
    Up to 300 mm (12") 2% 26, 24 3000 mm (10') S-lock or Standing Seam
    22+ Butt Seams*
    300 - 900 mm (12" to 36") 4% 24 3000 mm (10') S-lock or Standing Seam
    22+ Butt Seams*
    900 mm or greater 6% 24 1200 mm (4') S-lock or Standing Seam
    22+ Butt Seams*
    * Refer to 13.3.4 Seams
  10. To minimize oil-canning of metal flashings attached vertically, without the use of stiffener ribs or cross-breaking, the following standards apply to pre-finished galvanized steel, which is the most commonly used material for metal flashings. The Design Authority should specify slope, gauge and length using the standards in the table below:
    Table 13.2 Pre-finished Galvanized Steel Vertical Flashing (Gauge and Length Standards)
    Vertical Face Gauge Maximum Flashing
    Segment Length
    Vertical Seam Options
    Up to 150 mm (6") 26 3000 mm (10') S-lock
    Up to 200 mm (8") 24 3000 mm (10') S-lock
    Up to 300 mm (12") 22+ 3000 mm (10') Butt Seams*
    * Refer to 13.3.4 Seams
  11. Drip edges are not required, but strongly recommended for Linear Metal Flashings around the outside perimeter of a building, in order to protect wall finishes, and when drip edges are used they must extend at least 12 mm (1/2”) from the vertical face.
  12. All Linear Metal Flashings, regardless of their profile or application, must be hemmed.
  13. Where a parapet intersects with a wall, water must be directed to the outer surface of the wall by flashing the union with
    1. membrane flashing.
    2. membrane gussets at the corners.
    3. a metal saddle assembly.
  14. When flat butt seams are specified (as permitted by these Standards), their design and material requirements must conform to the Application standards in 13.3.4 (9).
  15. All membrane flashing terminating on any vertical surface must be secured to the vertical substrate by the contractor. Exposed membrane edges must also be protected from UV radiation, and from water intrusion. This must be accomplished using one of the following options, ranked according to the maintenance they require (low to high):
    1. Adhere the roof membrane to the wall surface, and
      1. protect the exposed membrane edge with overlapping wall membranes and exterior sheathing (Figure 10.1a).
      2. cover the exposed membrane edge with a secondary, fleece-reinforced 2-component liquid membrane flashing (see 10.3.8 Liquid Membrane Flashing for application requirements) (Figure 10.1b).
    2. Mechanically secure the membrane to the wall with a termination bar; caulk the upper edge of the termination bar, and cover the bar with a cut reglet flashing sealed inside the reglet cut with an acceptable sealant (see 13.2.4 Sealants) (Figure 10.1c).
    3. When the use of a cut reglet is impractical, a surface reglet flashing may be used:
      1. Mechanically secure the membrane to the wall with a termination bar or metal flashing; caulk the upper edge of the termination bar, and cover the bar with a secondary metal surface reglet flashing that is separately attached to the wall and sealed along the upper edge with an acceptable sealant (see 13.2.4 Sealants) (Figure 10.1d).
      2. Mechanically secure the membrane to the wall; surface-mount a reglet flashing above the terminated membrane and seal the metal flashing along the upper edge with an acceptable sealant; install a second surface-mounted reglet flashing and seal it along the upper edge with an acceptable sealant (see 13.2.4 Sealants) (Figure 10.1e).

  16. For fastener spacing, see additional Standards in 13.3.1 General (Application). For specific construction requirements, refer to the Construction Details Division in this Manual.

2 Materials

2.1 Sheet Metal Grade and Gauge

  1. A mill certificate must be provided by the Contractor when requested by the Design Authority.
  2. The following minimum gauges and / or weights of commonly used metals or alloys are acceptable for use in the RoofStar Guarantee Program.


GALVANIZED STEEL: minimum 0.50 mm (0.0196", 26-gauge) galvanized steel sheet, conforming to ASTM A653 / A653M-06 CS Type B, Z275 (G90) coating. Thickness tolerance as per ASTM A924/A924M-06 ±0.08 mm (0.003") for sheet widths not exceeding 1500 mm (60").
ALUMINUM – ZINC ALLOY COATED STEEL: minimum 0.50 mm (0.0196", 26-gauge) aluminum-zinc alloy coated steel sheet, conforming to ASTM A792/A792M-06 CS Type B, AZM150 (AZ50) coating. Thickness tolerance as per ASTM A924/A924M-06 ±0.08 mm (0.003") for sheet widths not exceeding 1500 mm (60").
ALUMINUM: minimum 0.80 mm (0.032", 20-gauge) aluminum sheet, utility quality to CSA HA Series - 1975, plain or embossed finish. Maximum thickness tolerance variation ± 0.06 mm (0.0025") based on 1200 mm (48") wide sheet.
STAINLESS STEEL: minimum 0.38 mm (0.014", 28-gauge) stainless steel, Type 302, 304, 316, 2B finish to ASTM A167-82. Maximum thickness tolerance variation ± 0.04 mm (0.0015") based on 1200 mm (48") wide sheet.
COPPER: minimum 0.56 mm (0.022", 16 oz.) copper sheet, cold rolled roofing copper to ASTM B370-81. Maximum thickness tolerance variation ± 0.09 mm (0.0035") based on 1200 mm (48") wide sheet.
ZINC: minimum 0.80 mm (0.031") zinc Sheet conforming to European standard EN 988-1996. Maximum thickness tolerance variation ± 0.03 mm (0.0012").
Specifying authorities should indicate the type and gauge of metal required, as well as the qualifying standards. The reference standard for gauges is USS REV (metric in mm).

2.2 Pre-painted Finishes

  1. When a painted finish on Linear Metal Flashings is specified, only SMP and PVDF pre-painted finishes are acceptable. Where Architectural Metal Roofing is installed, adjoining Linear Metal Flashings must have the same finish as the metal panels (PVDF).

2.3 Fasteners

  1. All fasteners used to secure metal flashings must be No. 8 corrosion-resistant screw or expansion fastener with a low-profile head and must be compatible with both the metal flashing material and the substrate.
  2. Cladding fasteners (screws) with gasketed washers, used as exposed fasteners for Linear Metal Flashings, must be No. 8 or larger, and must be made of metal compatible with, and corresponding in colour to, the flashing material.
  3. Blind rivets are acceptable for securing two Linear Metal Flashings together.
  4. Nails are not acceptable as fasteners.

2.4 Sealants

  1. Sealants shall be
    1. non-hardening high quality butyl or polyurethane.
    2. available in either gun grade or sealant tape form.
    3. suitable for exterior use and able to resist the effects of weathering.
    4. compatible with, and able to adhere to, the materials to which they are applied.
  2. Sealants 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”.
    4. CAN / CGSB-19.24, “Multi-Component, Chemical Curing Sealing Compound”.

3 Application

3.1 General

3.1.1 RoofStar 15-Year Guarantee

  1. Only Linear Metal Flashings fabricated from 24-guage stock (or thicker) qualify for a RoofStar 15-Year Guarantee.

3.2 Fabrication

  1. Drip edges are not required, but strongly recommended for flashings around the outside perimeter of a building, in order to protect wall finishes, and when drip edges are used they must extend at least 12 mm (1/2”) from the vertical face.
  2. All Linear Metal Flashings, regardless of their profile or application, must be hemmed.
  3. The vertical face of cap or counter-flashings must drop vertically at least 62 mm (2 ½”), not including the drip or hemmed edge.
  4. Metal edge flashings must be fabricated with a
    1. flange measuring no less than 100 mm (4") in width.
    2. vertical drop and hemmed drip edge at least 50 mm (2").
    3. sloped drop (for transitions to lower Water-shedding Systems) of no less than 100 mm (4").
  5. Metal edge flashings may be constructed with or without an upstand at the outside edge. Linear Metal Flashings designed for a draining roof edge may perform best without an upstand (for example, when transitioning to a lower water-shedding roof).

3.3 Securement

  1. Unless otherwise provided for in these Standards, mechanical fasteners used to secure Linear Metal Flashings shall be spaced no more than 300 mm (12”) O.C.
  2. Screw fasteners must penetrate the substrate a minimum of 19 mm (3/4”).
  3. Regardless of the type of linear metal flashing, all flashing fasteners must be installed at least 87.7 mm (3 ½") above the Finished Waterproofing System.
  4. Canted edge metal flashings may be mechanically fastened from the outside face.
  5. Hidden metal clips must
    1. be at least 24-gauge .
    2. be fastened as close to the bottom edge (hook) as practical but must not be fastened further than a maximum of 75 mm (3") from the bottom edge (hook).
    3. engage drip or safety edges by a minimum of 12 mm (½").
  6. Hidden metal clip types include
    1. Continuous Concealed Clips, which must be attached with fasteners spaced nor more than 300 mm (12") O.C.
    2. Discontinuous Concealed Clips, which must
      1. consist of a single clip centred between the seams of each length of metal flashing.
      2. measure at least 1/3 of the length of flashing it will secure but shall not be less than 100 mm (4") in length.
      3. be fastened with screws spaced no more than 300 mm (12") O.C.
  7. Fastening the top (horizontal or sloped) surface of a flashing with exposed fasteners is not permitted.
  8. Linear Metal Flashings secured in a reglet must be
    1. installed above the membrane flashing.
    2. inserted at least 12.7 mm (1/2”).
    3. friction-fitted within the reglet (groove) or secured on the exposed face with an acceptable fastener.
    4. sealed with a continuous bead of tooled gunnable sealant.
  9. Sealants must be tooled to positively shed water.

3.4 Seams

  1. All joints between lengths of flashing must be fully seamed.
  2. Regardless of the seam type, allowances should be made for metal expansion and contraction.
  3. Sealant applied to S-lock or Standing Seams is not a requirement of these Standards, but when it is specified
    1. the sealant must be applied along the full length of the seam.
    2. any sealant that extrudes from the seam during the seaming process must be removed and discarded (see 1.5 Workmanship).
  4. With the exception of flashings made with 22-gauge metal (or heavier), only S-lock seams or standing seams are acceptable when connecting lengths of flashing. See the standards and tables below.
  5. Notwithstanding other standards in this Manual, when Linear Metal Flashings join at a corner (regardless of the angle), the top face(s) of the flashings must be joined with a standing seam.
  6. Flat overlapped seams are acceptable only where
    1. the height of an inside corner is less than 100 mm (4").
    2. vertical flashings are lapped to fit under counter flashing or equipment flanges.
  7. Standing Seams must incorporate clips when the seam is longer than 100 mm (4”), and the clips must be
    1. fabricated from flat metal stock 24-gauge or heavier.
    2. at least 38 mm (1-1/2”) wide.
    3. spaced apart from each other no more than 200 mm (8”) O.C.
    4. secured with at least 2 acceptable low-profile flat head screws.
  8. S-locked Seams must be secured through flashing tab (leaf) with at least one (1) acceptable low-profile flat head screw when the seam is longer than 100 mm (4”), but fasteners must not be spaced more than 200 mm (8”) O.C.
  9. Flat Butt Seams are permissible only for cap flashings, and only when the flashing is fabricated from steel or aluminum ranging in thickness from 22 to 18-Gauge (the same applies to the equivalents for copper and zinc sheet material, by gauge or weight):
    1. Each flashing must have a hemmed front edge fabricated to hook onto a supporting saddle.
    2. Each supporting saddle must be
      1. manufactured from the same material as the flashing.
      2. formed to match the profile of the cap flashing.
      3. fabricated with a hook along the front face.
      4. secured to the parapet with screws.
      5. installed to underlap the butt joint by at least 100 mm (4”) on either side.
      6. seated in two parallel beads of un-tooled sealant or butyl tape, which must be applied between the saddle and flashing, on either side of the butt joint, to all three adjoining faces.
      7. secured to the cap flashing along both faces of the parapet (see 13.3.3 Securement).
    3. When cap flashings span widths greater than 300 mm (12”), the cap flashing must be riveted to the saddle to ensure adequate securement, and the rivets must be no further apart than 200 mm (8”).
    4. When the specified cap flashing material is thicker or heavier than 18-gauge steel or aluminum, the seam and securement design must be submitted to the Guarantor for review prior to tender. This review requirement also applies to copper and zinc flashings that exceed the permissible weight or gauge range.
  10. Notwithstanding the foregoing, refer to the standards in Table 13.1 and Table 13.2 (13.1.2 Design) for seams, metal gauge and flashing length requirements applicable to metal cap (coping) flashings.

3.5 Cap, Counter and Base Flashings

  1. Cap flashings must be fully supported by a substrate and require a hidden clip to fasten the outside face. The inside face of cap flashings may be secured with
    1. a hidden clip.
    2. cladding fasteners (see Materials above), which must be evenly spaced between seams along each length of flashing. Use no fewer than
      1. three (3) fasteners for every 3000 mm (10') length of metal flashing.
      2. two (2) fasteners for every 2400 mm (8') length of metal flashing.


    Fasteners may not be used on the outside face of cap (coping) flashing.

  2. All exposed faces of adjoining lengths of cap flashings must be connected with Standing Seams or S-locks, unless otherwise provided for in this Manual. See also 13.3.3.3 Securement.
  3. When the outside face of a cap flashing is concealed by a wall assembly, only the outside face may be lap-seamed, provided the overlap is no less than 100 mm (4”) and the overlapping metal is embedded in mastic.
  4. Counter-flashings must be secured to the vertical face, with fasteners or a reglet.
  5. When the specified cap flashing material is thicker or heavier than 18-gauge steel or aluminum, the seam and securement design must be submitted to the Guarantor for review prior to tender. This review requirement also applies to copper and zinc flashings that exceed the permissible weight or gauge range. See also Butt Seams, 13.3.5 (9).
  6. Metal base flashings are required for walls and curbs when the roof system incorporates gravel ballast and filter fabric or where a Vegetated Roof System is installed. Metal base flashings must “kick out” minimum 50 mm (2") over insulation and filter fabric. Filter fabric must be tucked up behind the base flashing.
  7. Metal base flashings may be fashioned as one piece, but in the alternative, a 2-piece flashing comprised of a lower counter-flashing is the recommended approach, to facilitate roof maintenance. Install flashings in keeping with other Standards found in this Manual.
  8. When the roof membrane is mechanically secured with a termination bar or a metal flashing,
    1. the termination bar profile should be capable of supporting a continuous bead of sealant.
    2. a surface reglet flashing must have a hemmed top edge bent outward from the face of the wall by at least 45° and the bent, hemmed edge must measure at least 15.9 mm (5/8”) from the break.
    3. fasteners must be spaced no more than 300 mm (12”) O.C.
    4. sealant must continuously fill the groove or top edge of the termination bar and be tooled to shed water away from the wall.
  9. When a second surface reglet flashing is installed to protect a termination bar or first surface reglet flashing used to secure the membrane,
    1. the flashing must be fabricated with a hemmed top edge bent outward from the face of the wall by at least 45° and the bent, hemmed edge must measure at least 15.9 mm (5/8”) from the break.
    2. it may fastened no more than 600 mm (24”) O.C., provided the metal flashing maintains continuous contact with the substrate.
    3. sealant must continuously fill the groove and be tooled to shed water away from the wall.
  10. Where parallel and overlapping reglet flashings are used, the joints between flashing segments must be offset by at least 300 mm (12”), except at corners.

3.6 Metal Edge Terminations

  1. Metal edge flashings (including Gravel Stop flashings) must be installed according to the standards in 10.3.5.2 Metal Edge Terminations.

3.7 Canted Edges

  1. New and existing canted edges must be covered with a metal flashing and secured to the outside face of the cant with cladding fasteners, which must be evenly spaced between seams along each length of flashing. Use no fewer than
    1. three (3) fasteners for every 3000 mm (10') length of metal flashing.
    2. two (2) fasteners for every 2400 mm (8') length of metal flashing.
  2. Metal fabrication and fasteners must conform to the material standards published in this Part.
  3. When, for aesthetic reasons, a face-fastened canted edge is not desirable, cants may be replaced with
    1. a metal edge roof termination (10.3.5.2 Metal Edge Terminations).
    2. a parapet, designed and constructed in keeping with the minimum height (see 10.1.2 Design), membrane flashing and metal flashing standards found in this Part.