BCAB #853 - Uniformity of Treads & Risers, Article 188.8.131.52.
April 9, 1986
Re: Uniformity of Treads & Risers, Article 184.108.40.206.
With reference to your letter of March 5, 1986, regarding the uniformity of treads and risers.
Article 220.127.116.11. of the Code requires that treads and risers have a uniform rise and run in any one flight. The example indicated consists of both curved and parallel stairs in the same flight, and for this situation we consider that the risers should be uniform. Run dimensions should be uniform between parallel treads, and uniform between curved treads, but a difference between the two types is acceptable, subject to each conforming with the required Code dimensions.
On the question of uniformity there should be a degree of tolerance, and while this is not indicated in the Code, we regard a variation of 5 mm as reasonable.
If the stairs fall within these parameters we consider them acceptable under the B.C. Building Code.
J.C. Currie, Chair