What building code requirements apply to chimney repair and repointing in Ontario?

Chimney repair and repointing in Ontario are governed by several sections of the Ontario Building Code (OBC), and whether you need a permit depends on the scope of the work. Cosmetic repointing of mortar joints and minor repairs generally do not require a permit, but structural repairs, rebuilds, and any work affecting the flue lining do.

For cosmetic repointing — grinding out deteriorated mortar joints and filling with new mortar — no building permit is required in most Ontario municipalities, including Toronto, Mississauga, Brampton, and other GTA cities. This is classified as routine maintenance. However, the work must still comply with OBC standards for mortar type and application. The mortar used for repointing must be appropriate for the brick type and exposure conditions. OBC Section 9.20 and CSA A179 (Mortar and Grout for Unit Masonry) govern mortar specifications. For most GTA chimneys built after 1945 with standard clay brick, Type S mortar is appropriate — it provides high compressive strength and excellent weather resistance for the severe exposure a chimney endures. For heritage chimneys on pre-war homes with softer brick, lime-based mortar (Type O or Type K) must be used. Using modern Portland cement mortar on heritage brick causes spalling — the hard mortar forces freeze-thaw stress into the softer brick, which cracks and flakes instead of the mortar. This is one of the most common and costly mistakes in GTA chimney work.

Structural chimney repairs require a building permit. This includes rebuilding a chimney above the roofline, rebuilding the chimney crown, installing a new flue liner, and addressing structural cracking or leaning. OBC Section 9.21 covers chimney construction requirements, including minimum wall thickness, flue liner specifications, clearance from combustibles, and height above the roofline. A chimney must extend at least 900mm (3 feet) above the point where it passes through the roof and at least 600mm (2 feet) higher than any part of the building within 3 metres (10 feet). If your chimney has been shortened or is below these heights, a rebuild to code height requires a permit.

Chimney crown repair and replacement falls into a grey area. A simple patch of an existing crown with appropriate mortar or crown sealant does not typically require a permit. However, removing and replacing the entire crown — which involves forming and pouring a new concrete cap — is generally considered a repair that should comply with OBC specifications for chimney caps, including a drip edge overhang and proper slope to shed water.

Flue liner work is regulated under OBC Section 9.21 and CSA B365 (Installation Code for Solid-Fuel-Burning Appliances and Equipment). If the chimney serves a wood-burning fireplace or wood stove, the flue liner must be clay tile or an approved stainless steel liner that meets CSA standards. Parging the interior of a flue (interior flue parging) to seal deteriorated clay tile joints is common, but if the clay tile liner is cracked or damaged beyond cosmetic repair, a stainless steel liner must be installed. This work requires a permit and inspection.

WSIB coverage is essential for any chimney contractor. Chimney work involves heights, scaffolding, and significant fall risk. Under Ontario law, homeowners who hire contractors without WSIB coverage can be held personally liable for workplace injuries. Always request a current WSIB clearance certificate before any chimney work begins. Scaffolding costs for chimney access typically add $500–$1,500 to the project, and a full chimney repointing in the GTA runs $1,000–$5,000 depending on chimney size, height, and condition.