- Had the same headache last winter—plaster just crumbles if you look at it wrong.
- Tried caulking straight onto bare spots, no dice. Ended up using a shellac-based primer first. Smells awful, but at least the caulk held longer.
- Out-of-square? I usually scribe the trim too, but sometimes you’re just chasing your tail. Even after all that, there’s always a cold draft somewhere.
- Honestly, with these old houses, “good enough” is usually the best you’ll get. Anyone who promises perfect lines probably hasn’t worked with 100-year-old walls.
Trimming out windows in these old houses really is a special kind of challenge. I remember the first time I tried replacing the trim in my 1920s bungalow—thought I’d just pop off the old stuff and slap on new, but the wall behind it looked like Swiss cheese. Plaster just flaked away every time I touched it. Ended up having to patch with setting-type joint compound, which helped a bit, but honestly, nothing’s ever truly flat or square.
I’ve also tried caulking straight onto the rough spots, but like you said, it doesn’t stick for long. Someone once told me to use an oil-based primer, but I went with BIN shellac too. The fumes are brutal, but it does seem to lock down the dust and make caulk grip better. Only downside is the cleanup—brushes never recover.
Out-of-square openings are the real kicker. I’ve had to scribe trim so aggressively that the back side looks like a skateboard ramp. Sometimes I’ll even back-bevel the casing on the table saw just to get it to sit flush against the wall. Still, there’s almost always a spot where light peeks through or some weird gap shows up after painting. I used to obsess over it, but now I just aim for “looks good from five feet away.”
I do think a lot of folks underestimate how much movement there is in old houses, too. Even if you get it perfect one year, by next winter there’s a new crack or draft. I finally stuffed some wool insulation behind the trim before nailing it up, which helped with the cold spots, but it’s not a miracle fix.
Curious if anyone’s tried those pre-made foam backer rods before caulking? I keep hearing about them but haven’t given it a go yet. Might be worth a shot, especially for the bigger gaps that show up out of nowhere.