How to Fix Leaky Dormers

Determine the entry point of the moisture on the inside of the dormer. Is it coming in through the ceiling, walls or around the window? Inspect the area closest to the entry point first.

Inspect the condition of the caulking around the exterior of the window. If it is cracked, has holes, or is deteriorated, remove the old caulking and replace with new.

Inspect the flashing around the window. At the top of the window there should be a drip edge flashing that extends out and bends down. This directs the water away from the top of the window. If it is not present remove the window and install the correct flashing around the opening.

Inspect the shingles on top of the dormer and up the roof line to the peak. Look at the condition of the shingles for widening of the gaps, curling of the edges, shingles missing, cap shingles blown off and any prior patches. If any of these conditions exist remove the existing shingles and re-shingle the entire roof.

Inspect the condition of the flashing on the exterior of the dormer where its vertical sections meet the roof line. There should be step flashing where vertical section meets the roof and counter flashing overlapping that. If caulking was used along the flashing, inspect its condition. If the flashing is missing install step flashing up the side of the dormer. If the caulking is old, remove the caulking and replace with new caulking.

Inspect the condition of the exterior wall sheathing on the vertical sections of the dormer. Look for holes or imperfections which may provide a path for the water to enter the inside of the building. If the wall sheathing is defective, remove the sheathing and install new sheathing to stop water from entering at this point.

Think about the location of sinks, toilets, showers and other sources of water in the house. If there is a logical reason plumbing would be run through the walls of the dormer, and the interior entry point of the water is near this location, cut a hole in the interior drywall with a drywall saw. Inspect the plumbing for leaking and correct any defective pipes.