BCAB #1723 - Drains for Roof Deck, Clause 22.214.171.124.(1)(b) (2006 BCBC)
January 17, 2013
Re: Drains for Roof Deck, Clause 126.96.36.199.(1)(b) (2006 BCBC)
The project in question is a new single family dwelling with a roof deck over the main entry. The roof deck is about 5.4 square metres in area with less than one square metre being over the living space of the first storey. There is a 150 mm high parapet around the deck and two 2 inch drains have been provided.
Reason for Appeal
Clause 188.8.131.52.(1)(b) requires building assemblies that are exposed to precipitation to "prevent ingress of precipitation into interior space." The rough opening and finished sill of the door providing access to the roof deck are below the top of the parapet.
The appellant contends that the pair of two inch drains provided are considerably more than required by the Code. The appellant calculates the hydraulic load from the roof deck is 140 Iitres and the Code allows up to 1700 Iitres for a two inch leader. Prevention of water ingress at the door sill has been carefully considered. The installation includes laying the torch-on roofing membrane over the sub-sill and then sealing between the sub-sill and the PVC door sill and between the PVC door jamb and wall sheathing membrane, which is wrapped into the rough opening, with backer rod and sealant.
Building Official's Position
The building official maintains that Clause 184.108.40.206.(1)(b) is not satisfied by the roof drains because they could both be blocked at the same time allowing water to enter the interior of the house over the door sill which is lower than the top of the parapet. To conform with Clause 220.127.116.11.(1)(b) the door sill needs to be above the level of the top of the parapet or an emergency overflow/scupper needs to installed below the level of the door sill.
Appeal Board Decision #1723
It is the determination of the Board that Part 5, and therefore Clause 18.104.22.168.(1)(b), does not apply to the building in question. There are no provisions applicable to the building in question that require scuppers or dictate the height of a door sill above a roof deck. The roof deck is drained in accordance with Section 9.26. and the deck drains are installed in conformance with requirements for roof drains in Part 7.
George Humphrey, Chair