Template:PERIMETER FLASHINGS - METAL (WP)
Template:PERIMETER FLASHINGS - METAL (WP)
1 General
All protrusion and penetration flashings, vents, curbs, sleepers, pipes cable, drains, etc. shall NOT be installed LESS than 200mm (8") from the base of walls, cants or installed equipment, protrusion or other penetration flashings.
Metal base flashing shall be kept approximately 25 mm (1") above gravel to prevent immersion in water with the exception of protected and modified protected waterproofing systems.
Gravel-stop type flashings may be used, provided manufacturer's printed instructions are followed The exceptions are overflow drains and roof scuppers that are installed through walls. These items are to be located by others.
Sheet metal flashings are designed to divert water away from the membrane flashing termination, usually onto the roof. The metal flashing also protects the membrane from deterioration due to the elements and from mechanical damage. The metal flashing is not a waterproofing membrane, therefore the roofing membrane should be continuous under the metal (see Metal Flashing Details).
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. The Architectural Sheet Metal Manual is available from:
- Sheet Metal and Air Conditioning Contractors National Association, Inc.
- c/o British Columbia Sheet Metal Association
- 156 - 4664 Lougheed Hwy Burnaby, B.C. V5C 5T5 (604) 299-4641
2 Material Selection
The following minimum gauges and / or weights of commonly used metals or alloys will be applied to all projects under the Guarantee Program. The length of metal flashing shall be limited to a maximum of 3.04 m (10').
GALVANIZED STEEL: 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").
ALUMINIUM – ZINC ALLOY COATED STEEL: 0.50 mm (0.0196", 26 gauge) aluminium-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").
ALUMINIUM: 0.80 mm (0.032", 20 gauge) aluminium 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: 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: 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: 0.80 mm (0.031") zinc Sheet conforming to European standard EN 988-1996. Maximum thickness tolerance variation ± 0.03 mm (0.0012").
3 Attachment
The use of concealed in-seam fasteners is required. Any fastening of metal flashings on the top of parapet surfaces is strongly discouraged and is not permitted as the only attachment method.
If top-surface fastening must be used because of a specific job site condition, only appropriate screw-type fasteners with neoprene washers may be used. Nails are not acceptable. The outside and inside face of metal cap flashing must be attached with cladding fasteners (screws), and/or concealed clips. Continuous and discontinuous concealed clips and or cladding screw fasteners or a combination of these attachment methods are acceptable to secure metal cap flashing. No fastening of flashing is permitted within 87.7 mm (3-1/2") of the roof surface. Note: Cladding fasteners or concealed clips are not required on the inside face of roof edge cant strip details.
Cladding fasteners (screws) with gasketed washers, used as exposed fasteners for metal flashing, must be No. 8 or better, made of metal compatible with and corresponding in colour to, the flashing material being installed. Nails are not acceptable as exposed fasteners. The minimum number of cladding screws used to face fasten metal cap flashing shall be three (3) fasteners equally spaced (±10%) between seams of flashing formed from 3000 mm (10 ft.) metal stock and a minimum of two fasteners equally spaced (±10%) between flashing seams formed from 2400 mm (8 ft.) metal stock. Concealed clips, both continuous and discontinuous, shall be formed from the same metal type as the flashing being secured and be minimum 24 gauge in thickness. In addition, concealed clips are to 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). Concealed clips must engage drip or safety edges by a minimum of 12.7 mm (1/2").
Continuous Concealed Clips are to be attached with appropriate corrosive resistant fasteners spaced at a maximum of 300 mm (12") o/c. Discontinuous Concealed Clips shall consist of a single clip centred between the seams of each length of metal flashing. Clips shall be a minimum of 1000 mm (40") in length for flashing formed from 3000 mm (10 ft.) metal stock and a minimum 800 mm (32") in length for 2400 mm (8 ft.) metal stock. Discontinuous clips for shorter flashing lengths shall be approximately 1/3 the length of the metal flashing but not less than 100 mm (4") in length. Corrosive resistant fasteners for clips, to be spaced a maximum of 300 mm (12") o/c.
4 Curb Heights
On all waterproofing assemblies the minimum curb height (equipment curbs, vent curbs, etc.) shall be 200 mm (8") above the roof surfacing. Surfacing is defined as the top of the waterproofing assembly, regardless of the type of wearing course.
5 Seams
Standing seams and S-lock seams are both acceptable.
Seaming of inside corners shall be carried to the base of the cant or the base of the metal. S-locks shall be fastened before the insertion of successive flashings. .2 Lap seams are acceptable only where the vertical run on the inside corner is less than 100 mm (4").
When the vertical height exceeds 300 mm (12"), standard seaming practices will be followed. When cants are not used on curbs, standard seaming practices (standing seams) shall be followed at all times, with the exception of the vertical flashing portion that is lapped to fit under counter flashing or equipment flanges.
For roof curb-flashing seams ( e.g. equipment, skylights, etc.), which do not exceed 300 mm (12") in height, lap-type seams may be used on the vertical portion provided standing seams are used in the cant area.
The design authority shall choose and specify the seaming system.
6 Cap Flashings, Base Flashings and Reglets
The top surface of walls (parapets, expansion joints, firewalls, roof dividers, etc.) wider than 100 mm (4" nominal) shall be constructed to provide positive slope to drain and be covered with metal cap flashing. Provide a reglet for all flashings terminating in concrete or masonry walls. When wall flashing terminates in a reglet, typically on high parapet walls, a coping flashing is required at the top of the parapet wall (see Metal Flashing Details). On new construction projects reglet and sloped wood blocking at top surface of concrete or masonry walls are to be installed by others.
Metal base flashings are required on all walls and curbs on roof systems that utilize gravel ballast filter mats, and must “kick out” minimum 50 mm (2") over insulation and filter fabric.
Reglet must be 200 mm (8") minimum to 300 mm (12") maximum above the waterproofing surface. Waterproofing surface is defined as the top of the waterproofing assembly, be it membrane or ballast.
In the case of multi-wythe masonry, composite walls, or parapets, and where not restricted by seismic codes, continuous flexible thru-wall flashings must be supplied and installed (by others), at the next course above the reglet or, alternatively, the inside of the parapet wall must be completely flashed or cladded.
Metal base flashing is required on all vertical surfaces, walls, curbs, etc. when hot asphalt is used to adhere stripping (flashing) membranes.
7 Flashing on Stucco Walls
On stucco-faced walls, only 2-piece flashings are permitted. The upper piece, retaining the stucco, must have a vertical flange to extend behind stucco and building paper. Stucco stops are not considered metal counter flashings.