Template:ROOF PENETRATIONS and DRAINS (SBS)
Template:ROOF PENETRATIONS and DRAINS (SBS)
Flanges - All roof flanges in contact with asphaltic membranes of any type shall be primed both sides with membrane manufacturers approved primer and embedded in a trowel coating of compatible mastic. Flanges are to be a minimum of 100 mm (4") wide.
Lead flanges in contact with asphaltic membranes of any type shall be embedded in a trowel coating of compatible plastic cement. Priming is not required.
All vent plumbing flashings shall be constructed of non-ferrous material.
All roof 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, eaves and other roof equipment, protrusion and penetration flashings. The exceptions are overflow drains and roof scuppers that are installed through walls. These items are to be located by others.
2 Gum Pans (Sealant Pockets)
With the exception of one on-site formed double standing seam corner joint and adjoining lapped flange joint, all flange corners shall be closed and soldered. Use only membrane manufacturer’s approved proprietary urethane based structural sealants to fill gum pans or pitch pockets.
Install a back-up storm collar whenever practical. This detail should be avoided; only use gum pans or pitch pockets as a last resort when other methods are impractical.
3 Liquid Membranes
Refer above to 11.3.2 Liquid Membranes for RoofStar Guarantee Standards and Guiding Principles governing the application of reinforced and non-reinforced liquid membrane flashing.
4 Strip-in Flashings
4.1 Strip-in Type Vents
- Strip-in type roof penetration flashings (lead, aluminium, stainless steel, copper, etc.) must be properly sized to fit pipe penetrations or alternatively, when pipes are irregular in size, spray foam urethane insulation may be used to fill gaps between pipes and flashings. Strip-in type roof penetration flashings are only permitted for use with single pipe roof penetrations, must incorporate properly fitted settlement caps, and be a minimum height of 200 mm (8") above finished roof surfaces. Pipes that are higher than standard flashings must have site formed non-bituminous flexible roof membrane storm collars sealed with compatible sealants and stainless steel clamps. Where shrink-wrapped terminations are employed, they shall be fitted with a stainless steel mechanical compression strap, and sealant shall be applied between shrink-wrap and penetration.
- The use of lead jack flashings is not permitted for use on torch applied membrane roofs.
- Strip-in type flashings for cables and multiple roof penetrations including grouped pipes and or cables must be purpose made roof flashings. All purpose-made multiple penetration flashings must provide a positive weather seal by use of manufacturer’s proprietary rubber based friction seals, mechanical clamps or gooseneck type design, and be a minimum height of 200 mm (8") above finished roof surfaces. Alternatively, roof curbs with metal hoods may be used to seal cables and multiple roof penetrations.
- Strip-in vents will not be permitted for use in protected or modified protected membrane roofs. Curb mounting for all venting units and equipment except lead or aluminium jacks is mandatory. Curbs are to be supplied and installed by others. Curbs are to be a minimum 200 mm (8") in height above top of finished surfacing.
- Strip-in type vents are permitted up to 350 mm x 350 mm (14" x 14"), equal to approximately 0.12 meter squared (196 sq. in.) on exposed or conventionally-placed membrane roofs, provided the vents are not located in or near a valley and are well drained.
- All strip-in flanges shall have fully soldered seams up to 200 mm (8") above roof level, and all open corners of flanges shall be filled in and soldered watertight. Flanges shall be mechanically attached on all nailable decks and unless specified otherwise adhered only on non-nailable decks, with a membrane compatible sealant.
- All galvanized steel strip-in flange style penetration and protrusion flashings installed on low slope roof systems, with slopes of less than 1:50 (1/4” in 12”),` shall have a proprietary membrane manufacturer approved rust resistant coating site applied from the base of the roof flange up-stand intersection to a minimum height of 100mm (4") above the finished roof surface.
4.2 Strip-in Curbs
- are to be a minimum 200 mm (8") in height above top of finished surfacing.
- are to be supplied and installed by others.
All purpose-made multiple penetration flashings must provide a positive weather seal by use of manufacturer’s proprietary rubber based friction seals, mechanical clamps or gooseneck type design, and be a minimum height of 200 mm (8") above finished roof surfaces.
Metal wall base flashing is optional with these application methods.
Guardrails should be installed only on vertical surfaces; attachment of guardrails to a horizontal surface is strongly discouraged. Where guardrails are fastened through the top of copings, the base of the guardrail shall be flashed with a compatible reinforced membrane flashing material, applied according to the primary membrane flashing manufacturer’s specifications.
Guardrails shall not direct water into a roof system by means of weep holes or the method of fastening, and mounts and flashings shall be installed at least 87.7 mm (3 ½”) above the roof surface.
For reference, see Construction Detail D1.7.9-4 Miscellaneous Penetrations (Guardrails)
5 Roof Drains and Scuppers
A roof drain, in this Manual, means “a fitting or device that is installed in the roof to permit storm water to discharge into a leader.” (BCPC, Division A, Part 1). A leader “means a pipe that is installed to carry storm water from a roof to a storm building drain or sewer or other place of disposal” (BCPC, Division A, Part 1). An overflow is a secondary roof drain that serves as a safeguard when roof drains fail.
Roof drains are comprised mainly of two parts: a bowl or flange that is affixed to the roof deck with mechanical fasteners or a proprietary clamping mechanism; and an integral drain stem that connects the bowl or flange to the leader. Roof drains are sized according to the diameter of the drain stem. The appropriate size and number of roof drains for any given roof area is determined by the relevant municipal and/or provincial building code in force (ref. BCPC, Division B – Part 2; 22.214.171.124 Hydraulic Loads from Roofs or Paved Surfaces).
Roof drains can be further classified as internal or external. Internal roof drains are connected to leaders located and connected to a storm building drain or sewer inside the exterior surface of a building. External roof drains drain storm water outside the exterior surface of a building. External roof drains may connect to leaders. Any requirements for leaders and connections to leaders may be found in the applicable municipal and provincial building and plumbing codes (ref. BCBC, 126.96.36.199 Accumulation and Disposal).
Roof drains and other roof accessories are to be installed as per membrane manufacturer's instructions.
5.1 Internal Roof Drains
All drains shall be connected to internal leaders only with mechanical compression type seals. “O”- rings, mastics and caulking are not acceptable methods for sealing internal roof drains to leaders.
5.1.1 Cast-iron Roof Drains
All cast-iron roof drains must be flashed as follows:
- .1 A minimum 14.6 kg / m² (3 lb / sq ft) lead sheet. The flange must extend a minimum of 150 mm (6") beyond the perimeter of the drain and be embedded in compatible mastic. The lead flange must extend a minimum of 25 mm (1") into the bowl. The trade supplying the roof drain shall supply the lead flashing material.
- .2 A 1 m x 1 m (39" x 39"), 3 mm thick modified bituminous base sheet may be used in place of lead flashing on cast drains. The base sheet must be embedded in compatible mastic on the drain bowl flange and extend a minimum of 25 mm (1") into the bowl.
When cast-iron roof drains are used; a sump receiver and under-deck clamp must be provided and installed by the trade supplying the roof drain. In addition, the trade supplying roof drains must also provide secondary stainless steel debris strainers in addition to primary drain strainers on all roofing systems that utilize gravel ballast and or growing mediums (soil). Only the use of drain manufacturer’s proprietary secondary stainless steel debris strainers is acceptable.
5.1.2 Flange-type Roof Drains
Flange-type drains typically include
- Bowl-style drains with an extended flange, and
- flat drains without a bowl
Drains for use in the RoofStar Guarantee Program must be hot-welded at the joints between the bowl/flange and drain stem.
All flange type roof drains shall be constructed of non-ferrous material and include a primary drain strainer. Flanged copper drains shall be formed from a minimum weight of 16 oz. sheet copper for external (on outside of walls) drains and 24 oz. sheet copper for internal (inside walls or buildings) drains. The minimum gauge for aluminium sheet to be used for roof drains shall be 20 gauge for external use and 12 gauge for internal use.
On all roofing systems that utilize gravel ballast and or growing mediums (soil), the trade supplying roof drains must also provide secondary stainless steel debris strainers. Only the use of drain manufacturer’s proprietary secondary stainless steel debris strainers is acceptable.
5.2 External Roof Drains
5.2.1 Scupper Drains
A scupper drain may serve either as a primary roof drain or as a secondary drain. A scupper drain passes through a wall or parapet, and is connected to a drain leader outside the building envelope. Scupper drains must incorporate a continuous flange surrounding the drain box, measuring at least 100 mm (4”) in width, and must be manufactured with welded seams and joints, and made from non-ferrous metals, subject to the Material Selection standards for metal found in this Manual.
All scupper drains shall be formed with a minimum 37.7 mm (1 ½") lower outside faces than side walls of the water collection boxes and incorporate minimum 12.7 mm (½") drip edges on the lowered outside faces.
Scupper drains shall be installed according to the prevailing municipal building code and the British Columbia Building Code (latest edition).
An overflow is only a secondary drain that serves as a safeguard when primary drains fail. Overflows must incorporate a continuous flange surrounding the drain box, measuring at least 100 mm (4”) in width, and may be manufactured from ferrous metals, subject to the Material Selection standards for metal found in this Manual. Heights and locations of roof drains are the responsibility of the Design Authority. The RoofStar Guarantee Program recommends the installation of overflows
- when the perimeter wall height above the roof membrane exceeds 100 mm (4”)
- no higher than 100 mm (4”) above drain elevations
- in locations where their discharge of storm water will be visible.
Overflows are required when low doorway or low window details are used (see D1.7.8-4 Water & Drainage (Open Wall Scupper) and D1.7.8-5 Water & Drainage (Through-wall Scupper)). In these applications, the overflow must be installed at least 1” lower than the elevation of the door or window sill.
Overflows shall be installed according to the prevailing municipal building code and the British Columbia Building Code (latest edition).
Where no overflows are specified, the building structure must be designed to carry the total load of water collected on the roof, in the event of the failure of roof drains (see BC Building Code, latest edition). The RoofStar Guarantee Program accepts no responsibility for roof failure where overflows are not specified or installed.