Why Does My Chimney Leak When It Rains? Flashing, Mortar and the Cricket

Brick chimneys are everywhere in Victoria's pre-1950 neighbourhoods: Fairfield, Oak Bay, James Bay, Fernwood and Rockland homes often have two, and many have been decommissioned since the switch to gas furnaces and heat pumps while still standing through the roof. The original flashing was galvanised steel or lead let into the mortar joints, and after 80 winters the counter flashing has often rusted, pulled out or been buried under three generations of roofing cement. Victoria's dry summers, about 14 mm of rain in July at Gonzales, bake and crack crowns that the wet season then soaks.

The 1960s and 70s homes of Gordon Head, Royal Oak and Colwood have a different chimney: a framed chase clad in siding or stucco around a metal flue. Those leak at the cap and the siding-to-roof junction rather than at masonry, and the wide ones frequently have no cricket behind them, so needles and water sit against the upslope wall. Wherever the chimney is, if it sits near the eave rather than the ridge it collects the whole slope's runoff and fails sooner.

A chimney is a hole in the roof with a rigid object in it that moves differently from the roof in heat and cold. The joint between them is where the four common failures live.

• Step flashing: L-shaped pieces woven with each shingle course up the sides; they rust, lift or are re-used at re-roof.
• Counter flashing: the metal let into the mortar joint that covers the step flashing; it pulls out as mortar erodes or was replaced by a bead of sealant.
• Crown and mortar: a cracked concrete crown or open joints let water into the brick, which then shows up inside as damp masonry rather than a drip.
• The cricket: a small peaked saddle on the upslope side that diverts water around a wide chimney; without one, water and needles pool against the brick.

Most chimney leaks in older Victoria homes have already been 'fixed' at least once with roofing cement or a tube of sealant along the flashing. It holds for a season or two, then the chimney and roof move, the bead cracks, and the leak returns, now with the original flashing buried under tar so the next roofer has to cut it all out. A proper repair replaces the step and counter flashing with new metal, embeds the counter flashing in a cut mortar joint, and adds a cricket where the chimney is wide. Masonry problems, the crown and the joints, are a mason's work and are often done at the same time.

Inside, the attic framing around the chimney shows staining and tells whether water is coming from the flashing (wet at the roofline) or through the masonry (wet on the brick faces). On the roof, the inspection covers the overlap of step flashing with the shingles, how deeply the counter flashing is set, the condition of the crown, cap and mortar, whether a cricket exists, and the shingles immediately upslope. Because a chimney leak often only shows in wind-driven rain, telling the roofer when it happens helps.

In our pricing model a chimney re-flash is $400 to $1,500 before GST, with masonry crown and repointing priced separately by a mason. RoofingCalculatorHQ's 2026 Canadian calculator puts flashing replacement at $310 to $1,250 with a typical job at $390 to $540, which fits the simpler end. If the roof is within a few years of replacement, the flashing is usually done as a line item of the re-roof, since the shingles have to come off around the chimney anyway. Homeowners with an unused chimney sometimes have it removed below the roofline at re-roof and the deck closed over, which ends the leak permanently; a contractor prices that case by case.