Roof Leak Where the Roof Meets a Wall or Dormer: What May Be Wrong

Dormers and sidewalls are the signature of Victoria's character housing: the 1900s to 1930s homes of Fairfield, Oak Bay and Rockland have shed and gable dormers on nearly every slope, and many were stuccoed in the 1950s straight over the original flashing, so there is no counter flashing to speak of and the stucco itself is the last line of defence. The James Bay and Fernwood cottages add lean-to additions whose roofs meet the old back wall under a strip of tin and tar.

Newer homes have the same junction in a different place. The two-storey plans of 1990s Broadmead and 2000s Langford, Colwood and Bear Mountain put a garage or porch roof against the upper wall, and the kick-out flashing at the bottom of that sidewall was often omitted or cut short. Years of southeasterly rain then run down inside the siding, and the first sign is a soft spot at the base of the wall or a stain in the room below, well away from the roof.

Wherever a roof meets a vertical wall, three pieces of metal do the work. A professional will check each in turn.

• Step flashing runs up a sidewall: one L-shaped piece per shingle course, each overlapping the one below, tucked behind the siding or house wrap.
• Apron (headwall) flashing runs across the top of a roof section that ends against a wall, lapped under the wall cladding and over the shingles.
• Kick-out flashing sits at the bottom of a sidewall, bent outward to push the water running down the step flashing into the gutter rather than behind the siding.
• Counter flashing or the cladding itself covers the top edge of the step flashing; on stuccoed Victoria homes that is often just stucco.

Water that gets behind a sidewall flashing does not fall straight down onto the ceiling. It runs down the sheathing inside the wall, soaks the framing and shows as a stain at a window head, a soft baseboard or a bubbling patch of paint a floor below. The missing kick-out is the classic case: the roof looks fine, the ceiling is dry, and the wall at the corner of the porch roof is rotten. By the time it shows, the repair may include sheathing and framing, which is why a wall-junction leak carries high urgency even when the drip is small.

Outside: the weave of the step flashing, whether the apron runs under the cladding, the presence and length of the kick-out, the condition of any counter flashing, and the siding or stucco laps immediately above the roof line. Inside: the attic or ceiling space behind the dormer for staining on the wall sheathing, and the wall below for softness. On a stuccoed heritage home the roofer may recommend a building-envelope contractor look at the wall as well, because the fix can involve cutting stucco to install proper counter flashing.

In our pricing model a wall or dormer flashing repair is $400 to $1,500 before GST and a section of shingles beside it $800 to $2,500. That covers new metal woven into the existing roof where the shingles are still flexible enough to lift. Two things push the price up: brittle shingles that crack when lifted, which turns the repair into a section replacement, and siding or stucco that must be cut back and reinstated to get the flashing in, which is envelope work priced separately. If the roof is due within a few years, all dormer and wall flashings are normally renewed as part of the replacement.