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Caulking exterior window trim to keep out water from coming inside?

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  • Oct 26th, 2020 8:32 pm
[OP]
Sr. Member
Mar 14, 2006
968 posts
467 upvotes
Coquitlam

Caulking exterior window trim to keep out water from coming inside?

We plan to replace our window trim and repaint our house in the Spring of 2021. In the meantime one of our window trims is starting to rot and the caulking around the trim has started to break away from the window trim. I caulked around that entire window (top of trim, right side of trim, left side of trim, and bottom side of trim) last week to try to hold off any water entering the house until we re-trim our windows in the Spring.

3 days after I caulked around the window and after some rain I noticed some brown water marks on the interior window ledge on that specific window. I don't recall seeing brown water marks on the interior window ledge before I caulked the exterior trim last week and it seems like my caulking last week seems to have now made the water enter our house where it wasn't really a problem before. Someone once told me that I shouldn't caulk on the underside of the window trim......Is that what I did wrong or if not what should I do to stop the water from entering from the window?
6 replies
Deal Guru
User avatar
Mar 13, 2004
12620 posts
4230 upvotes
Ontario
Post some photos, But yes ideally you need to leave a space at the bottom so IF water enters somehow it can escape through the bottom.
SPACEMANRICK wrote: We plan to replace our window trim and repaint our house in the Spring of 2021. In the meantime one of our window trims is starting to rot and the caulking around the trim has started to break away from the window trim. I caulked around that entire window (top of trim, right side of trim, left side of trim, and bottom side of trim) last week to try to hold off any water entering the house until we re-trim our windows in the Spring.

3 days after I caulked around the window and after some rain I noticed some brown water marks on the interior window ledge on that specific window. I don't recall seeing brown water marks on the interior window ledge before I caulked the exterior trim last week and it seems like my caulking last week seems to have now made the water enter our house where it wasn't really a problem before. Someone once told me that I shouldn't caulk on the underside of the window trim......Is that what I did wrong or if not what should I do to stop the water from entering from the window?
[OP]
Sr. Member
Mar 14, 2006
968 posts
467 upvotes
Coquitlam
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Here are some photos that I just took today. The spoon on the ledge is the area where I found the brown water color marks 2 days ago. It rained quite heavy last night but there were no water marks this morning ..... perhaps the rain and wind was not blowing towards the window last night???

Excuse the poor caulking job but I haven't really caulked before and I did it last week when it was starting to get dark outside. Thanks for any advice and help offered!
Deal Addict
Nov 17, 2012
4171 posts
3384 upvotes
Toronto
If the water mark is showing up on the surface of that ledge (is it wood?) where the spoon is sitting, then the water is most likely coming from above, and somehow running around the window pane. It may be a leak of the casement window on the right or left of the fixed pane in the center where the spoon is. Might not have anything to do with your caulking job.

You could beef up the caulking across the top of the trim, but there is also white aluminum flashing (I think I see that) which is under the trim, coming out over the top of the window. So that should be protecting the window to a degree.

If you want to really test it, close the windows tight (use the locks always to pull them in sealed) and spray the hose against the window concentrating on the seam where the window is closed.

Also trim that shrub a bit so the branches aren't touching the window/wall.
Deal Fanatic
User avatar
Jun 21, 2003
5310 posts
2553 upvotes
Stoney Creek, ON
Did you make sure the area was dry before caulking? If there was still water or lots of moisture I don’t believe the caulking will attach to the surfaces and could just form a gap between the wall and caulking.

Also did you check application directions in terms of temperature and moisture exposure? The cheaper the tube the less tolerant it is to temperature range, humidity and the longer time it needs to cure before rain or moisture contacts it. As said above caulking is not something to go cheap on.

You should definitely at the very least redo the caulking on top. I’d check Google images to see what it should look like up there. You want it to be done in a way that ensures the water runs off of it, not just pools around it.
Deal Guru
User avatar
Mar 13, 2004
12620 posts
4230 upvotes
Ontario
If you want to make it look nice you need painters tape (usually blue or green) and you tape each side and apply in the middle then go over it with your finger or a plastic spoon. Have a look at this video they explain it.

Sr. Member
Feb 26, 2019
559 posts
590 upvotes
Ottawa
Redo the caulking for now. Use Mulco Supra Expert or Mulco Flextra. That should get you guy until spring when you redo the exterior trim.

Who ever you hire, specify that you want them to replace the trim and install head flashing. Properly installed head flashing is supposed to go under the house wrap beneath your siding/stucco and shed water to the outside of the window using a proper piece of rigid aluminum flashing. Make sure your contractor is planning to do this.

If you rely on caulking only (and no flashing) it is only matter of time before caulking fails and water finds its way in. You are learning that now.

Not a big job, but it will cost you extra, make sure it’s included in the scope of work.

https://www.finehomebuilding.com/2016/1 ... d-flashing
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