BCAB #1736 - ABS Shower Drain Through Concrete Slab, Sentence

September 24, 2013

BCAB #1736

Re: ABS Shower Drain Through Concrete Slab, Sentence

Project Description

The project in question is a hi-rise condominium of noncombustible construction. The appeal involves a site-constructed shower base employing an ABS drain through the eight inch concrete slab. The ABS drain pipe penetrates the slab through a cUL classified firestop device conforming to ULC-S115 and then connects to noncombustible piping directly below the slab with a combustible flexible coupling.

Reason for Appeal

With some exceptions Sentence permits combustible (plastic) piping to be used in noncombustible construction provided it has a flame spread rating not exceeding 25 and, in high buildings, a smoke developed rating not exceeding 50. The one exception to the flame spread and smoke developed limits that could apply to this project is where the plastic pipe is “concealed in a wall or concrete floor slab.”

Appellant's Position

The appellant contends that all but 2 inches of the ABS pipe is concealed in the concrete floor slab and the 2 inches projecting below the slab is concealed by the flexible coupling. This transition from combustible to noncombustible pipe is similar to the common situation of combustible pipe projecting above a slab on ground and then transitioning to noncombustible pipe up through the building. The appellant notes that Appeal #1098 considered the flexible coupling to be an acceptable combustible element in noncombustible piping systems.

Building Official's Position

The building official maintains that Sentence clearly only allows combustible piping that has a flame spread rating of not more than 25 and a smoke developed rating of not more than 50 for hi-rise buildings. ABS pipe has a flame spread rating of 200 – 260.

Appeal Board Decision #1736

It is the determination of the Board that the ABS shower drain exceeds the permitted flame spread rating and is not “concealed in a . . . concrete floor slab” because it is visible from below the slab.

George Humphrey, Chair