SBS Cast Iron Drains

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SBS Cast Iron Drains

Division D - Construction Details

SBS Cast Iron Drains

Notice to Reader
Images used in a Construction Detail are representative and not prescriptive. Nor are they necessarily drawn to scale. Rather, they are provided to visually convey the requirements of the Standard they represent. Unless otherwise required by the Standard, dimensions, the selection of materials and their application remains the responsibility of the Design Authority.

The full text of the referenced requirements in the Standard may be read by using the blue hyperlinks
SBS Details


(1) Supporting Deck Overlay
If required by design authority.
(2) Air or Vapour Control Layers
If required by design authority.
(3) Insulation
Mechanically fastened. See available insulation products in the Accepted Materials section of this Manual.
(4) Insulation Overlay
Asphalt adhered or mechanically fastened. Two layers required over heat-sensitive insulation.
(5) Primary Membrane and Membrane Protection
(6) Mastic
As approved by manufacturer.
(7) Base Membrane Flashing
As approved by membrane manufacturer (See (C) below).


(A) Acceptable Supporting Deck Structure
(B) Roof Drain Assembly
(C) Lead Flashing
Minimum 15 kg / m² (3 lb / ft²) weight lead sheet; flange extending minimum 25 mm (1") into bowl to 150 mm (6") beyond perimeter of drain; embed in mastic (6) and prime top surface where required by manufacturer or minimum 1 m x 1 m (39" x 39") 3 mm thick modified bituminous base sheet; to be supplied by trade supplying roof drain. For optional installation methods that use a membrane flashing in place of lead, see the Application requirements under Cast-iron Roof Drains.
  • Leader size is determined by using the calculation found in the BC Building Code at Appendix P.7.4.10 and Section (Section for gutters)(current edition) in conjunction with the 15-minute rainfall value from the National Building Code, Appendix C.

NOTE: See the Standard for additional requirements.

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