Interesting take, but I'm wondering if shims are always necessary. I get your point about uneven foam expansion and alignment issues, but I've installed a couple windows myself without shimming and haven't noticed any real problems yet. Granted, it's only been about two years, so maybe issues could pop up later?
I did make sure the frames were pretty close to square before installing though—maybe that's why I've gotten away with it so far. Or maybe it's just luck? I don't know. It seems like if you're careful enough with the foam and don't go crazy overfilling it, you might be able to skip shims in some cases.
Not saying you're wrong at all—your experience clearly shows there's a risk—but maybe it's more of a case-by-case thing rather than an absolute must-do step? Curious if anyone else has tried skipping shims and had long-term success or failure.
I've skipped shims on a couple windows too—going on three years now, no issues yet. Sounds like you took your time squaring things up, which probably helped. I'd say you're fine, just keep an eye out for drafts or sticking down the road.
Skipping shims can work out fine if you're lucky and your framing is spot-on, but honestly, I'd still recommend using them. Shims aren't just about squaring things up—they also help distribute weight evenly and prevent the frame from warping over time. Even a tiny bit of settling or seasonal expansion can cause issues down the line. You're probably good for now, but if you ever notice sticking or drafts creeping in, adding shims later isn't too tough...just a bit of a hassle.
Totally agree about the shims. Learned that one the hard way when I skipped them on a basement window—seemed fine at first, but after a couple winters it started sticking like crazy. Ended up redoing it anyway...lesson learned, haha.
"seemed fine at first, but after a couple winters it started sticking like crazy."
Haha, sounds familiar... I had a similar experience with a kitchen window. Thought I'd save myself some hassle by skipping the shims—big mistake. It opened smoothly for about a year, then one humid summer day it just refused to budge. Ended up wrestling with it every morning until I finally gave in and redid the whole thing properly. Funny how shortcuts always seem to cost more time in the end...
Had pretty much the same issue with a bedroom window a few years back. Installed it myself, thought I nailed it—everything measured twice, leveled perfectly, but I totally underestimated how much expansion and contraction wood framing goes through over the seasons.
- First winter: smooth sailing, felt proud of myself.
- Second summer: slight sticking, nothing major—ignored it.
- Next winter: window practically welded shut every cold morning. Had to use a hairdryer to warm up the frame just to get it open.
- Eventually realized I'd left too little clearance around the frame, causing friction when things expanded or contracted.
Ended up pulling off the trim and shaving down the rough opening slightly to give it some breathing room. Added proper insulation and reinstalled everything carefully. Hasn't given me trouble since.
It's amazing how sensitive windows are to small installation details. Even a minor oversight can turn into a daily annoyance down the road. Learned my lesson though... never underestimate seasonal movement!
Went through something similar last year when I replaced a couple of windows in my living room. Thought I had accounted for everything—measured multiple times, shimmed carefully, and even watched a bunch of tutorials beforehand. Still ran into issues:
- First few months were fine, no sticking or drafts.
- Summer rolled around, and suddenly one window started binding slightly at the top corner.
- Realized later I'd underestimated how much direct sunlight hitting the frame could cause uneven expansion.
Ended up removing the trim again (ugh...) and adjusted the shims to give it a bit more wiggle room. Also switched to low-expansion foam insulation instead of fiberglass batting, which seemed to help stabilize things better.
One thing I'd add is that it's not just seasonal temperature swings—humidity levels can really mess with wood framing too. Learned the hard way that even small moisture changes can cause noticeable shifts. Now I keep a closer eye on indoor humidity, especially during summer months.
Interesting about the sunlight causing expansion—hadn't really thought about that before. Did you find the low-expansion foam easier to work with than fiberglass, or was it mostly just better performance-wise? I've always used fiberglass batting since it's what I'm familiar with, but now I'm wondering if foam insulation might be worth the switch next time I tackle a window project...
"Did you find the low-expansion foam easier to work with than fiberglass, or was it mostly just better performance-wise?"
I've done window installs both ways, and honestly, foam insulation was a bit of a game-changer for me. Fiberglass batting is straightforward, sure, but it can be messy and itchy—plus, it doesn't always fill those tiny gaps perfectly. Low-expansion foam, once you get the hang of it, really seals those spaces up tight. I noticed fewer drafts and better soundproofing almost immediately.
The first time I tried it though...let's just say there was a bit of a learning curve. (Pro tip: wear gloves and have some acetone handy, trust me.) But after that initial fumbling around, I found foam quicker and cleaner overall. Definitely worth experimenting with next time you're tackling windows. Just remember to use the low-expansion stuff specifically designed for doors and windows, since regular foam expands way too aggressively. Learned that one the hard way too...
Yeah, foam's definitely better performance-wise, but I wouldn't say it's always easier. First time I used it, ended up with sticky fingers for days... Fiberglass is itchy, sure, but at least it doesn't glue your hands together. Still, foam's worth the hassle once you get used to it.