When I swapped out the old drafty windows in my 1960s ranch, I realized the new vinyl replacements were a tad smaller than the original wood frames. Here’s how I tackled resizing the openings—hopefully without making a mess of my drywall.
First, I measured the new window and marked out where the framing needed to shrink. Pulled off the old casing and sill, then used a recip saw to cut back any extra framing (had to be careful not to nick wires hidden in there). Next, I added new 2x4s to “fur out” the opening so it matched the size of the new window. Shimmed everything until it was square and level—honestly, that part took longer than expected. Once it all fit snug, I insulated around the frame, popped in the window, then sealed everything up.
I’m sure there’s other ways to do this—maybe less clumsy than mine? Anyone got tricks for getting a perfect fit or avoiding gaps?
I ran into the same sizing headache when I did my living room windows last summer.
Getting it all plumb is a pain, right? I found that using composite shims instead of wood helped me avoid splitting, but I still had to fuss with the fit for ages. Ever try low-expansion foam around the frame? That really closed up any tiny gaps for me, but you gotta be careful not to overdo it or the window bows.“Shimmed everything until it was square and level—honestly, that part took longer than expected.”
“Shimmed everything until it was square and level—honestly, that part took longer than expected.”
Yep, shimming is basically a patience test. I used composite shims too, but somehow still managed to drop half of them behind the wall... Low-expansion foam's great for drafts, but once I got a little heavy-handed and the window looked like it was trying to escape. Lesson learned: less is more with that stuff.
Funny, I actually had better luck with wood shims than composite ones—maybe I just have clumsy hands, but the composites always seemed to slip out of place for me. I hear you on the foam, though. The first time I used it, I thought “more must be better,” and the trim ended up bowed out. Ever since, I’ve just stuck with a thin bead and packed in some backer rod if there’s a bigger gap. It’s a little old school, but at least my windows don’t look like they’re about to pop out of the wall...
Yeah, I’ve definitely over-foamed a window or two myself—those cans are sneaky, you barely squeeze and suddenly it’s oozing everywhere. I’ve started using painter’s tape around the frame just in case, makes cleanup way easier if things get messy. For shims, I actually mix wood and composite depending on what’s handy, but I do think wood feels more solid. One thing I learned the hard way: double check for plumb before locking everything in. Thought mine was good, but the sash kept drifting open until I adjusted it.
double check for plumb before locking everything in. Thought mine was good, but the sash kept drifting open until I adjusted it.
That’s classic—been there myself. I swear, windows have a sixth sense for when you’re feeling confident. I did a bay window last summer and even with a level in one hand, the thing still wanted to lean like it was auditioning for Pisa. I lean toward wood shims too, just feels easier to fine-tune. Haven’t tried the painter’s tape trick, but after my last foam explosion, I might have to steal that one.
Funny how a window can look perfect until you let go and it does its own thing. I’ve honestly had more luck with composite shims than wood, especially in older plaster walls where things aren’t square to begin with. Painter’s tape does help keep foam under control, but nothing beats a slow hand and patience—learned that the hard way after a can of foam turned my trim into a science project.