I hear you on the “minimal expansion” stuff—honestly, I’ve had similar issues. Even when you’re careful, it always seems to mushroom out more than you expect. But I actually do think it helps with drafts if you get it in the right spots and don’t overdo it. The trick is patience... let it cure, trim carefully, and seal up any gaps with caulk after. That said, I’ve seen a few cases where the foam pushed the jamb out of alignment slightly, which is a pain to fix. For older wood windows, I sometimes just stuff backer rod and use flexible caulk instead—less mess, easier to undo later if you need repairs.
I hear you on the “minimal expansion” stuff—honestly, I’ve had similar issues.
Yeah, I’ve had foam push the jamb out before too—super annoying. You mentioned using backer rod and flexible caulk for old wood windows. Have you noticed any long-term issues with drafts coming back, or does that combo hold up pretty well over time?
Yeah, foam can be a real pain—especially with old wood frames that aren’t always square to start with. I’ve used backer rod and flexible caulk (usually a high-quality silicone or urethane) on a bunch of 1920s windows in our area. Honestly, if you prep the gap right and don’t skimp on the caulk, it holds up surprisingly well. I’ve gone back after 4-5 years and still had a decent seal, just needed minor touch-ups where the paint cracked. Only time I’ve seen drafts creep back is if the wood itself shifts or shrinks more than expected... which happens with these old houses. Not perfect, but way less hassle than dealing with over-expanding foam.
I hear you on the foam—tried it once on my 1915 windows and ended up scraping blobs off the plaster for hours. The backer rod plus caulk combo has been way less stressful for me, especially where the frames are all wonky. Only spot I had trouble was where a previous owner used some weird filler that cracked out, but otherwise, it’s held up better than I expected.
The backer rod plus caulk combo has been way less stressful for me, especially where the frames are all wonky.
Right there with you—foam is like glitter, once it’s out, it’s everywhere forever. I’ve sworn by backer rod for weird gaps, but if you ever run into that cracked filler again, a little wood hardener before caulking sometimes helps. Learned that one after chasing crumbling bits down the wall...
a little wood hardener before caulking sometimes helps. Learned that one after chasing crumbling bits down the wall...
Yeah, that crumbling filler is the worst. I’ve been there—tried to just caulk over it once and the gap came right back. These days, I do a quick scrape, brush on the wood hardener, let it set, then backer rod and caulk. Makes a world of difference, especially on those 1950s window frames where nothing’s square. The only thing I’d add: don’t rush the dry time on the hardener. It’s tempting, but if it’s still tacky, the caulk never really sticks right.
- Scrape out the loose stuff—don’t get lazy, even if it’s tedious.
- Hit it with wood hardener, but yeah, let it fully cure. If it’s even a little sticky, caulk just peels off later.
- On old frames, I sometimes have to double up: hardener, then a thin layer of epoxy filler if there’s a deep gouge.
- Backer rod is a lifesaver for wide gaps, but don’t jam it in too tight or you’ll get weird bulges.
- Never trust a 1950s window to be square…or even close. I keep a box of shims handy just in case.
Honestly, I’ve learned the hard way that patience at this stage saves a lot of cursing and rework down the road.
Yeah, patience really is the name of the game. I’ve rushed the prep before and paid for it with drafts and peeling caulk later. One thing I’d add—if you’re aiming for energy savings, don’t skimp on sealing those gaps, even if you have to get creative with backer rod or foam. My 1948 place had some wild angles…nothing like a cold breeze in January to remind you what you missed.
Totally hear you on the weird angles—my 1952 bungalow has corners that make you wonder if the builder had a few too many during framing. I used to think a bead of caulk would do, but after one winter with frost on the INSIDE of my living room trim, I got serious about air sealing. Ended up stuffing backer rod into some gaps so big I probably could've lost my keys in there. Spray foam helped, but I learned (the sticky way) to go easy near finished surfaces.
One thing I’ll say: don’t trust the old trim to hide everything. On my first go, I figured “it’ll be covered”—but those drafts find their way. Now, even if it takes an extra afternoon, I check every edge with a candle before putting the casing back up. Might look overkill, but when January rolls around and you’re not feeling that icy draft, it’s worth it.
That reminds me—did you run into any trouble with the old plaster or drywall crumbling when you pulled the trim? I’ve seen some real messes behind 70-year-old casings. Ever try those foam gaskets for outlets, too, or just stick to windows?