Just had some new windows delivered and now I'm kinda stressing about making sure they don't leak once they're in. My house is old (like 1950s, so nothing is square), and I remember my neighbor complaining about water seeping in around his frames last year. I want to avoid that whole mess if possible.
Do you guys have any tricks or products you swear by for sealing things up? I’ve heard mixed things about flashing tape vs. caulk, and someone mentioned expanding foam can actually make things worse if you overdo it. Is there a “right” order for layering stuff, or does it depend on the window type? Also, is it worth getting a pro for this part, or can a reasonably handy person pull it off?
Would love to hear what’s worked (or not worked) for folks, especially if you’ve got an older house like mine.
I’m in the same boat with a 60s-era house and nothing lines up right. I used flashing tape and caulk when I did my kitchen window—tape first, then caulk on the outside after it was set. Didn’t mess with foam, mostly because I kept hearing it can warp the frame if you use too much. Has anyone here actually had foam cause problems, or is that just internet paranoia?
Didn’t mess with foam, mostly because I kept hearing it can warp the frame if you use too much.
- Had the same worry. Used low-expansion foam on two windows in my 1958 place—just a thin bead, didn’t go wild.
- No warping for me, but I was careful not to overfill. I think it’s only a problem if you really pack it in.
- Tape and caulk combo is solid. Foam just helped block drafts in my case, especially in winter.
- Honestly, biggest issue was getting the old frames square enough for anything to seal right... nothing’s ever level in these old houses.
I’ve always been a little nervous about foam for that exact reason—heard too many stories about bowed jambs. Did a couple windows in my 1960 ranch, just a light pass with low-expansion stuff, like you said. No trouble, but I triple-checked every step. Tape and caulk are my go-tos for water, but on those windy winter days, foam made a noticeable difference. Getting the frame square is the real headache, though... nothing like trying to shim a window when the wall’s gone wavy over the decades.
Getting the frame square is half the battle, especially in an old place—mine’s got walls that look straight until you actually measure. I’ve had better luck with flashing tape than caulk for water, honestly. Caulk shrinks and cracks over time, but the tape holds up if you overlap it right. I do a layer of tape on the sill, set the window, then more tape up the sides and top, always lapping it so water runs out, not in. Only a tiny bead of caulk outside, just to keep wind-driven rain out. Expanding foam, I use barely any—just enough to fill gaps, not jam the frame. Never had leaks, but I’m stubborn about following the order. Wouldn’t say it’s rocket science, but patience matters more than fancy products.
I’m with you on flashing tape holding up better than caulk, especially in older houses where nothing’s ever truly square. I’ve found patience is the key too—rushing the taping step always comes back to bite me when the first big rain hits. I go a bit further and use a sloped sill pan (sometimes just made from folded flashing), which helps direct any water out, just in case something sneaks past the tape.
Curious if you insulate around the frame for energy efficiency? I use low-expansion foam, but I’m careful not to overdo it so the window doesn’t get pushed out of alignment. I’ve read some folks prefer backer rod and mineral wool instead of foam for breathability and to avoid trapping moisture, but I haven’t tried that myself yet. Have you noticed any difference in drafts or condensation with your approach? Always trying to find that balance between watertight and airtight without causing other issues...
Yeah, I’ve had better luck with low-expansion foam too, but I get nervous about overfilling and messing with the window alignment—been there, done that. Tried mineral wool once on a basement window and it seemed to breathe a bit better, but I still noticed a little draft. Might just be my old house settling, honestly. The sloped sill pan trick is something I wish I’d known about years ago... makes a big difference in heavy rain.
I get what you’re saying about low-expansion foam, but I’m not totally sold on it being the magic bullet. I’ve seen it shrink back a bit over a couple seasons, especially if there’s any moisture sneaking in. Had to pull trim off and re-do a section last fall—what a pain. Sloped sill pans are good, but if the flashing tape isn’t just right, water still finds its way in. Sometimes I wonder if the old-school method of backer rod and caulk wasn’t more reliable in these drafty old places...
Totally hear you on the foam—I've seen it shrink too, especially in spots that get a little damp. It’s great for drafts but not a cure-all. Backer rod and caulk definitely have their place, especially in older frames where nothing is square.
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Couldn’t agree more. Pre-folded sill pans help, but if the corners aren’t perfect, water sneaks in anyway.“if the flashing tape isn’t just right, water still finds its way in.”
- I’ve started using liquid-applied flashings on tricky installs—less user error than tape, but messier and takes longer to cure.
- Ever tried combining backer rod/caulk with modern flashing systems? I’ve had decent luck layering them up for extra insurance.
Curious if anyone’s found a good way to deal with irregular stone sills—those always seem to be the leakiest spots for me.
- Seen the same thing with stone sills—never totally flat, always a pain.
- What’s worked for me: flexible flashing membrane (the stretchy kind), pressed into every dip and wrinkle. It’s not pretty but it does seem to help.
- I’ll run a fat bead of high-quality exterior sealant under the sill before setting the window, then tool it in tight.
- Sometimes I wedge in backer rod if there’s a big gap, but honestly, it’s just about getting as much coverage as possible.
- Tried liquid flashing once on an old fieldstone opening... messy job, but it held up through two winters so far.
Stone’s just tough—nothing is square or smooth. Just gotta layer it up and cross your fingers sometimes.