I just noticed a major leak in one of my windows last weekend during a heavy rainstorm. Upon inspection, I found several gaps in the caulking that I think the water is getting through. I managed to get a tarp over the window for a quick fix, but I'd like to caulk as soon as possible.

How long do I need to let the window dry out before scraping the old caulk off and reapplying? I don't want to trap any excess moisture and end up with mold problems, but the longest stretch this week without rain forecasted is only two days. Is that long enough for everything to dry out? My home exterior surrounding the window is brick.

2 Answers 2


Alternative 1: Cut out the old caulk. Then take a heat gun, or if you don't have one, a hair dryer, and blow into the crack to speed up the evaporation. Use your judgement about how long to do this. Make sure you don't heat any adjoining cold glass or it may crack. You can shield glass with a wide bladed spackling knife, or ever a board. You could also set a fan up on something and let it blow several hours. To make sure the crevice is dry, take some toilet tissue and force it as far down in the crack as you can. Then pry it back out. If it comes out dry, caulk.

Alternative 2: Cut out the old caulk and let it air dry. Whenever rain is forecast, use duct tape to completely cover the area. After the rain finishes, uncover. If rain is forecast while you're waiting, reapply duct tape. After a week of air drying it should be dry. Then caulk.

  • I actually ended up using a heat gun anyway to soften and remove the old caulk in the areas there were cracks, so I'll accept this answer. Your second option wouldn't work since duct tape doesn't do a great job of sticking to masonry, especially if it's wet.
    – Doresoom
    Feb 8, 2014 at 21:48

Cut out the old caulk now to let it all dry out, that will open everything up to the maximum to allow for drying. If it is an older home it will still dry after it is caulked. One day to dry and one day to caulk and let it set will suffice for proper adhesion.

I suspect if the house is over 10 years old, it will not be an issue. It will still dry out. Newer homes may have a little more difficult time to dry out from the new vapor barriers out on the market.If you see drywall or plaster damage that has been around for a while, (wet is OK, water bubbles under the paint MAY be OK, black is bad) you may want to do a little removal to inspect inside the wall, just to be sure. Caulk takes a while to degrade and it does so with out notice, so check interior areas thoroughly.

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