BCAB #1209 - Fireplaces, Support for Corbelling Masonry in Smoke Chamber Section 9.22
May 18, 1990
Re: Fireplaces, Support for Corbelling Masonry in Smoke Chamber Section 9.22
Masonry fireplace and chimney for single family dwelling.
Reason for Appeal
Corbelling masonry in smoke chamber has been supported on steel rebar. The building official has rejected the chimney because of this and has requested the removal of the rebar.
The Building Code is silent on this issue. The CSA standard for masonry chimneys and fireplaces, CSA-A405-M87, requires that "metal angles shall be incorporated beside any sloping type smoke chamber domes to permit the corbelling of masonry."
Building Official's Position
Based on experience he does not consider rebar or metal angle iron an acceptable alternative to the corbelling requirements of Article 18.104.22.168. of Section 9.20, "Above-Grade Masonry." He has found significant cracking in the smoke chambers of existing fireplaces built in a fashion similar to the one in question.
Appeal Board Decision #1209
The CSA-A405 standard "Design and Construction of Masonry Chimneys and Fireplaces" does not apply, since it is not a referenced document in the B.C. Building Code 1985.
Therefore for corbelling, Article 22.214.171.124. applies. The use of "rebar" or metal angle for the support of corbelled masonry is not permitted unless considered under Section 2.5 Equivalents. Acceptance of equivalents is the responsibility of the local authority and not the Building Code Appeal Board.
George R. Humphrey, Chair