Roof-to-wall joints are one of the most common leak points on any house. The water usually shows up somewhere else, inside the wall or on a ceiling a few feet away, so the flashing is often the last thing anyone checks.
This is most common in homes built roughly 1940 to 1980. Post-war and mid-century — copper supply, aging cast iron stacks, 60 to 100 amp panels, first-generation central air.
1Why this joint leaks
- Continuous strip instead of steps. One long piece of metal laid along the wall cannot shed water course by course. The caulk line is all that keeps water out.
- Reused or rusted pieces. Old flashing left in place during a reroof can be rusted through or bent out of position.
- Siding pulled tight to the roof. Siding or trim that sits on the shingles holds debris and moisture against the joint.
- No kick-out at the bottom. Where the roof edge stops against a wall, water needs to be turned into the gutter. Without it, water runs down inside the wall.
2How to check it
- Look from a window or the groundLong smears of caulk or roofing cement along the wall line are a sign the flashing was not stepped.
- Check the bottom cornerLook where the lowest course meets the wall. Staining or rot on the siding below that corner points to a missing kick-out.
- Go into the attic or the room belowLook for staining on the framing or drywall near the wall after rain.
- Note the wall typeOn brick or stone the steps need a second piece, counterflashing set into the masonry, over the top of them.
3Fixing it
Do it yourself
- Spot-checking and photographing the joint
- Clearing debris trapped against the wall
- Temporary sealant to slow a leak until a roofer can come
Hire a pro
- Lifting shingles and siding to install proper step pieces
- Adding a kick-out at the bottom of the run
- Counterflashing on brick or stone walls
- Repairing any wet sheathing found behind the joint
Doing it properly means removing the courses along the wall and often the bottom of the siding, then weaving new pieces in as the shingles go back. More caulk over a continuous strip only buys time.
A joint that has leaked for years may have rotted the sheathing or the wall framing. Ask the roofer to tell you, in writing, what they found once the flashing was open.
4What drives the cost
The length of the wall run, the wall covering (siding comes off more easily than brick), the roof pitch and height, and any rot behind the joint set the price. Ask for the flashing and any sheathing repair as separate line items.
Talk to a roofer who will open the joint and check the flashing pieces, not just add sealant.
877-360-46575Questions
Can’t I just recaulk it?
That slows a leak, but sealant is the only defense on a continuous strip, and it fails in a few years. Stepped flashing is the lasting fix.
Should flashing be replaced during a reroof?
Ask for new step flashing in writing. Reusing old pieces is a common corner cut.
Why is the leak nowhere near the wall?
Water follows framing and sheathing before it drips. A leak a few feet from the wall can still start at the flashing.
Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.
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