Div. B › Part 9 › 9.22 › 9.22.3 — Fireplace Walls

9.22.3.1 — Thickness of Walls

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(1) Except as provided in Sentence (2), the thickness of the back and sides of a fireplace, including the thickness of any firebrick liner, shall be not less than 190 mm where a metal liner or a firebrick liner less than 51 mm thick is used.

(2) When a steel fireplace liner is used with an air circulating chamber surrounding the firebox, the back and sides of the fireplace shall consist of,

(a) solid masonry units not less than 90 mm thick, or

(b) hollow masonry units not less than 190 mm thick.

OBC Definitions

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chamber

means a structure in a shallow buried trench that is constructed with an open bottom and that contains a pressurized distribution pipe.

solid masonry

means a single-wythe or multi-wythe construction made of solid masonry units or semi-solid, cored or hollow masonry units, the cells of which may or may not be filled with mortar or grout. In multi-wythe masonry construction, the space between the wythes consists of a mortar-filled collar joint or grout-filled space and the wythes may or may not be constructed of the same masonry materials.

solid masonry unit

means a concrete block or brick unit, a clay brick unit or a calcium silicate brick unit, the net solid area of which is at least 75% of its gross area.

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