I’m a new homeowner and just noticed this small opening next to my upstairs window between stone and window. Is this caulk that’s used there or mortar? Any recommendations on how I should go about repairing?


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  • Please be more specific about the "crack". Maybe edit the picture with an arrow at or circle around the crack, or edit the question to describe in words where the "crack" is that you're concerned about. I see a little black area on the bottom right corner of the white window. I see what looks like a joint in stone work just below that corner, I see a dark area below the grey shutter. I'm not sure if any of these are what you're concerned about or if it's something else that I'm totally missing.
    – FreeMan
    May 29, 2022 at 16:40
  • @FreeMan I’m sorry I should have been more specific, I updated the post with a photo and circle around what I’m referencing in terms of crack - it appears something has deteriorated and is missing right there? Is that caulk?
    – Carl
    May 29, 2022 at 18:24

1 Answer 1


If the white stuff above the missing chunk is rubbery, then yes, it's caulk that has, for some reason fallen out.

If it is missing caulk, then you'll want to pick at the remaining bit above it to see if it's pretty well attached or if there is more that has come loose. I'd suggest that you poke at the whole thing, all the way to the top of the window. Use a flat blade screwdriver to gently poke it. You're not trying to damage good caulk, just check to see if any is loose and moves easily.

You'll want to remove any loose bits of caulk, particularly at the bottom where it's most likely that there would be additional loose bits. If there are a lot of loose spots, I'd suggest that you clean it all out - scrape & pry with your screwdriver, a razor blade/box cutter knife, putty knife or whatever you can get in there to remove as much old caulk as possible. If there isn't any more loose or just a bit at the bottom, use a knife of some sort to cut back to well attached existing caulk and make the best, cleanest cut you can, then scrape all the extra off.

The goal is to have a nice clean surface to apply new caulk to, and to not leave any loose bits of caulk in that gap. If the new caulk only sticks to old, loose caulk, then the new caulk will have gaps where water can get through. It's worth it to wipe the area down with a damp rag/paper towel to get dust and dirt off, too. You may as well start with it clean, and any dirt that's there will be embedded in the caulk and may cause the bond to fail early.

Once you've got it cleaned out, look at how deep into the wall that gap goes. If it's very shallow, you're good to go. If, however, it's pretty deep, you'll want to fill it with some foam backer rod. It's just what it says on the tin - it's made out of foam and you stuff it in the gap to fill most of it, then caulk over the surface. If it's too deep, you might just pump a whole tube of caulk into the wall and never get it to come out at the surface - the backer rod prevents that.

Pick a good quality white exterior caulk, put the tube in your caulk gun and squeeze it into the gap. Using a wet finger or the back of a plastic spoon, smooth it to a nice shape and ensure that it's well adhered to the sides, the old caulk, and the bottom.

There's a possibility that this is a vinyl window and that the missing piece is actually a piece of the vinyl that has cracked and fallen out.

If this is the case, contact the window manufacturer to see if there's a warranty on the windows and if they'll replace it. It would, most likely, require a complete replacement to take care of this - I doubt they'd have a trim piece that could go in there. If it's under warranty, though, it's all on them, so don't worry about it, just get them to schedule someone to come measure the window and order the replacement.

If it's not under warranty (window warranties probably aren't transferrable to the new owner, but it never hurts to ask), then you'll probably need to fill it with caulk following the procedure above but without the exploration looking for solid caulk, since there isn't any other caulk there. You might still need the backer rod so you're not filling potentially empty spaces in the window frame with your whole tube.

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