BCAB #1792 - Stair Nosings and Rakeback, Article 18.104.22.168.
January 27, 2017
Code Edition: 2012
Code Division: B
Code Reference: Part 3
Re: Stair Nosings and Rakeback, Article 22.214.171.124.
The project is a new exit stair in an existing medium hazard industrial occupancy building to which Part 3 of the 2012 British Columbia Building Code applies. The new exit stair is proposed to have steps with a rise of 180 mm and a run of 280 mm. It will be constructed with closed vertical risers (no rakeback) and with no nosings protruding beyond the face of the risers.
Applicable Code Requirements
Sentence 126.96.36.199.(2) states:
2) Steps for stairs referred to in Sentence (1) shall
- a) have a rise between successive treads not less than 125 mm and not more than 180 mm,
- b) have a closed riser, and
- c) have
- i) a riser with a rakeback of not more than 38 mm, or
- ii) the underside of the nosing with an angle of not less than 60° from the horizontal.
Decision Being Appealed (Local Authority’s Position)
The local authority has determined that vertical risers are not permitted.
In order to comply with Sentence 188.8.131.52.(2), the stair risers must have either a rakeback or extended nosing.
The appellant contends that a rakeback of 0 mm complies with Subclause 184.108.40.206.(2)(c)(i) and a nosing with an underside angle of 90° complies with Subclause 220.127.116.11.(2)(c)(ii), and concludes that a vertical riser complies with the Code.
Appeal Board Decision #1792
It is the determination of the Board that the subject stairs comply with Sentence 18.104.22.168.(2).
Reason for Decision
The intent of the Code is to limit excessive rakeback, and therefore 0 mm (vertical) is compliant. The Code does not require a nosing, but rather when a nosing is provided, there are specific provisions.
The Board does acknowledge that the Code language is not as precise as it could be.
Chair, Building Code Appeal Board