My casement window leaks water to the inside when it's raining. It has been leaking a while. It looks like it's leaking between the glass unit and the sash but the caulk between the glass and the sash on the outside does not look compromised.

How can I diagnose and fix the problem?

leaking window

  • Casement windows are hinged and swing horizontally, and should be pulled tightly closed by the operating mechanism against a weatherstrip. Have you inspected the "landing area" of the sash to see if there is a weatherstrip seal, in good condition? Does the operator mechanism firmly pull the sash closed? Jan 20, 2017 at 7:19
  • can you tell us the manufacturer of the windows and do you know how old they are? I have casement windows in my house that is 18 years old and they are starting to leak just like yours because the weather strip is start failing.
    – d.george
    Jan 20, 2017 at 10:25
  • They are jeldwen windows and I suspect they are 8-10 years old. The weather stripping looks ok, and the leak is appearing above the weatherstripping. I can't imagine a way the the water would get where it is if the weather stripping were the problem.
    – John
    Jan 22, 2017 at 19:21

2 Answers 2


Are you sure that the weep holes are not blocked? This issue should be notated in your owner's manual. Otherwise, the window may not have been correctly sloped and flashed in the frame, and it took this long for water infiltration to evidence. Is there rot on the underside of the window, when opened? Older Pella awning windows had a problem similar to this.


The issue was with insufficient prep/paint of the sash which allowed water and sun to warp the sash trim such that water could leak between the glass unit and the sash frame.

I have had some luck removing and replacing the sealant between the glass unit and the sash frame and then repainting the sash.


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