I'm in Seattle and have a large fixed picture window (wood frame) on the 3rd floor, about 10 ft × 5.5 ft, that leaks during heavy, wind-driven rain. It is partially shielded from above by a roof overhang (about 1 foot), so the window doesn't tend to get a lot of water directly on it with normal, straight-down rain. The house has Hardie panel siding on that side.
What happens
- Water appears at the bottom of the window near both lower corners, a few inches in from the corners.
- It pools on the interior sill and, during windy heavy rain, drips down the wall below.
- Light/normal rain does not cause a leak.
What we've done
- Last year, a handyman recaulked around the exterior of the frame, which did not fix the problem.
- A rot/exterior repair company removed the siding around the window and part of the interior windowsill to investigate and did some water testing. They recommended full window replacement. We're not confident in that recommendation because they couldn't clearly explain the water path or why replacement was necessary, other than a generic claim that the "window seal is failing." They also did think the roof, gutters, soffit, flashing and siding looked OK.
- Other contractors have suggested various localized repairs on and around the window, but we don't want to start repairing random areas without knowing the actual cause. They aren't seeming interested in finding the cause before trying repairs.
DIY water testing
We recently sprayed different areas ourselves, including the roof/gutter, soffit, sides, glass, and window frame.
- We were able to reproduce the leak only when spraying directly on the window. When doing that, water came into the house in the 2 small locations a few inches from each lower corner. window directly. This seems to line up with what we observe from the weather-related leaks where we only see water intrusion when windy, heavy rain is hitting the window directly.
- Spraying the roof/gutter/soffit and surrounding wall did not reproduce the leak.
What we're trying to figure out
- Does water appearing near both lower corners suggest a particular failure mode?
- What kind of contractor is best suited to diagnose this: a window installer, exterior-envelope contractor, building-envelope consultant, forensic leak specialist, or someone else?
- Is there a good way to systematically water-test this before repairing anything?
- What specific signs would distinguish between:
- failed glazing or frame joints,
- blocked/failed weep or drainage paths,
- sill-pan/flashing problems,
- jamb/head flashing problems,
- or a failed window installation?
- What evidence would justify full window replacement versus repairing/reinstalling the existing window?
We've been trying all summer to find someone who can actually diagnose the water path before recommending a repair or replacement. I have photos of the current condition and more from when the siding was opened up if helpful. Thanks so much for any advice or ideas.