I hear you on the foam, but I’ve had a couple windows where even the “slow and steady” approach left me with frames bowed just enough to mess with the sash. Maybe it’s just my luck—my house is a 1915 Craftsman and nothing’s square either. These days, I stick to shims for alignment and only use foam as a light filler, never for support. Learned that lesson after having to re-do a kitchen window that wouldn’t close right after one too many enthusiastic foam sessions…
“These days, I stick to shims for alignment and only use foam as a light filler, never for support. Learned that lesson after having to re-do a kitchen window that wouldn’t close right after one too many enthusiastic foam sessions…”
That sounds familiar… I’ve definitely had my share of “foam regret.” The first time I swapped out a window in my 1920s bungalow, I got a little too confident with the expanding stuff. Even going slow, it pushed the jamb just enough that the top sash was rubbing like crazy. Had to pull the whole thing, scrape out the foam, and start over with more patience (and a lot more shims).
What’s worked for me since then is treating shims as the actual structure—like you said—and only using a minimal bead of low-expansion foam once everything’s square and plumb. I wedge shims on all four corners and check with a long level (sometimes even diagonally) before touching the foam can. If anything’s off by even an eighth of an inch, it’ll show up when you try closing the sash later on.
One thing I started doing after fighting with old, out-of-square frames: cut custom shims from scrap cedar or pine instead of relying on the pre-made wedge ones. That way you can fill weird gaps without cranking things out of shape. Sometimes I’ll even double up thin shims to get just the right fit, especially when dealing with those “character” walls that bow or dip.
I think part of the headache is just old houses doing what they do—nothing is ever truly level or square. I’ve found that patience and dry-fitting everything twice saves way more time than you’d expect. And yeah, less is definitely more with foam. The stuff is great at sealing drafts but terrible at holding anything in place.
Funny how it always seems like “one more squirt” will fix it… and then you’re back with a pry bar cursing your optimism.
I get where you’re coming from with the shims-first approach, but I’ve actually had a few situations—especially with newer vinyl window units—where the right type of foam made a big difference in overall stability and insulation. I know the horror stories about bowed jambs and stuck sashes (been there, cursed that), but some of the modern low-expansion foams are way more predictable than the old stuff. If you keep the bead small and let it cure before trimming, I’ve found it can help lock things in place without shifting anything out of alignment.
That said, I totally agree about dry-fitting and checking for square like three times before committing. With old plaster walls and weird framing, nothing ever lines up the way you want. But sometimes, especially if you’re dealing with bigger gaps or out-of-plumb studs, a careful combo of foam and shims can actually get you a tighter seal and less draft down the line.
Guess it just depends on the house and how much “character” it’s got...
- Totally get where you’re coming from—older houses just love to throw curveballs.
- I’ve had decent luck with the foam + shims combo too, especially on my 1950s place where nothing is square. The low-expansion stuff is a game changer compared to the old days. Used to dread that “bulge” after foam cured, but now it’s way more predictable.
- That said, I still tend to go heavy on dry-fitting and shimming first, just because I’m paranoid about sashes binding later. Had one window years ago where I got impatient and ended up fighting it for weeks.
- For bigger gaps, I’ll admit, foam does make things easier. It’s a lifesaver when the studs are out of whack and you need a bit of forgiveness.
- Agree on checking for square—three times minimum. Sometimes I feel like I spend more time measuring than actually installing.
- Every house has its own “personality,” for sure. Sometimes you have to improvise and hope the next owner appreciates your effort... or at least doesn’t curse your name.
All in all, sounds like you’ve got a good system down. The mix of old-school and new materials is the way to go in my book.
Sometimes I feel like I spend more time measuring than actually installing.
That hits home. I swear, I’ve spent whole afternoons just checking for square and still end up second-guessing myself. You’re right about the foam—used to be such a mess, but the newer stuff really does make life easier. I’m with you on dry-fitting too. It’s tempting to rush, but I’ve learned (the hard way) that patience pays off in the long run. Sounds like you’ve got a good rhythm going—mixing old tricks with new materials really is the sweet spot for these quirky old houses.
Funny you mention dry-fitting—sometimes I feel like I spend half the time just triple-checking that the opening’s actually level, especially with these old plaster walls that aren’t ever quite straight. Do you find you have to shim one side more than the other, or is it just me? I’ve started using those composite shims, which help a bit, but I’m always curious how folks handle weird, out-of-square frames. Ever run into a spot where you had to adjust the rough opening itself?
I’m really glad you brought this up because I’ve been obsessing over the same thing. The walls in my 1950s place are nowhere near square, and I swear every window opening is its own weird shape. I definitely end up shimming one side more than the other—sometimes by a lot. Composite shims have been a lifesaver for me too, especially since they don’t split like wood ones.
There was one window where the gap on one side was so bad, I actually had to trim back a bit of the rough opening (which felt a little scary, not gonna lie). I used a multi-tool to shave off just enough, then rebuilt the area with some new framing and foam. Not sure if that’s technically “the right way,” but it worked and the window’s solid.
How do you keep track of level and plumb with all the shims in place? I end up checking with the level at every step, but it still feels like guesswork sometimes...
Man, I hear you on the rough openings—my 1940s place is just as quirky. Sometimes I think the original builders just eyeballed everything and called it a day. I’ve had to shave a stud or two myself, and yeah, it feels a little wrong, but sometimes you just gotta make it fit. I’m with you on composite shims too; I used to split wood ones constantly.
About keeping things plumb and level—honestly, I don’t totally trust just the level anymore. I started using a laser level across the jambs, and it’s made a big difference, especially when you’re fighting out-of-square frames. But even then, there’s a bit of “good enough” involved. I always wonder if I’m overthinking it, though. Like, at what point do you just accept the house is wonky and move on?
Ever tried those adjustable window brackets? I keep seeing them online but haven’t pulled the trigger. Supposedly they help with weird gaps, but I’m skeptical they’d actually save time.
Man, I totally get what you mean about that “good enough” threshold. My place is from the late ‘30s and half the time I’m convinced nothing is square except maybe the mailbox. I’ve had the same internal debate—do I keep fussing with shims and levels until the window is textbook perfect, or just call it when it looks right and operates smoothly? Honestly, I think you’re spot on: sometimes you just have to accept the character of an old house and not drive yourself nuts.
I haven’t tried those adjustable brackets either, but I’m skeptical like you. It feels like just another thing to fiddle with, and if it fails down the line, you’re back to square one. Composite shims have been my go-to too, even if they’re a little pricier. At least they don’t split when you sneeze on them.
It’s reassuring to hear someone else is wrestling with the same stuff. Makes me feel less like I’m butchering the place and more like I’m just keeping it alive.
Totally get the pain of chasing perfect level in an old house—sometimes it feels like the walls are actively fighting you. I’ve found that if the window opens, closes, and looks decent from five feet away, it’s good enough. Ever tried using a laser level just to see how far off things really are? Sometimes it’s better not to know…