Sill pans made a huge difference for me, too. I used to rely just on caulk and backer rod, but it never seemed to last through the freeze-thaw cycles—especially in these old wood frames that are anything but square. I’m always wary of over-foaming, since too much pressure can actually bow the jambs if you’re not careful. That tiny gap at the bottom is easy to overlook, but it’s crucial for drainage. Sometimes you have to pick your battles and accept that perfection isn’t really possible with 80-year-old openings...
That tiny gap at the bottom is easy to overlook, but it’s crucial for drainage.
This is exactly what tripped me up on my first window. I thought filling every gap was the way to go, but then I noticed condensation pooling under the sill—guess I basically created a mini fish tank. Did you use any specific type of sill pan, or just DIY with flashing tape? I ended up using one of those flexible plastic pans, but getting it to sit right in an out-of-square opening was a pain. Is there a trick to getting the pan to actually slope toward the exterior when the framing’s all over the place?
That’s exactly what happened to me—sealed everything up tight and then wondered why the bottom of the window was basically a puddle. I tried the flashing tape route at first, but honestly, it felt like I was just making a sticky mess. The flexible pans seem great on paper, but yeah, getting them to lay flat in a wonky opening is another story. I ended up shimming under the pan in a couple spots to force a slight slope outwards, but then I worried about compressing insulation or messing with the fit.
Have you noticed if your condensation issue improved after switching pans? I’m curious if there’s a sweet spot between over-sealing and just letting things breathe. Also, did you run into any issues with air leaks after leaving that gap for drainage? Seems like every fix comes with its own new headache...
I totally get what you mean about feeling like every fix just creates a new problem. When I did my kitchen window last spring, I went down the same rabbit hole—over-sealed everything because I was paranoid about leaks, and then ended up with condensation pooling at the sill. At first, I thought it was just the humid weather, but nope, it stuck around even on dry days.
Here’s where I might push back a bit: I actually had better luck with the flashing tape than the pans. The first time, yeah, it was a sticky disaster (I got some in my hair... still don’t know how), but once I slowed down and used a roller to really press it into the corners, it worked out okay. Maybe my opening wasn’t as wonky as yours though. The flexible pans looked promising in the videos, but when I tried one on a basement window that was definitely not square, it just kept popping up at the edges. Ended up cursing more than fixing.
About leaving gaps for drainage—I worried about air leaks too, but after reading way too many forums and watching those building science videos, I left a tiny weep path at the bottom and stuffed backer rod around the rest before foaming. Haven’t noticed a draft yet (knock on wood), but I do wonder if that’ll change once winter rolls around again.
Funny thing is, after backing off on sealing every single crack and letting things vent just a bit, my condensation actually got better. Maybe it’s just my old house being stubborn, but sometimes less is more? Still wish there was a magic product that did all this without turning into an arts and crafts project.
Curious if anyone’s tried those rigid metal pans instead of the flexible ones—seems like they’d be easier to shim without warping?
Man, the arts and crafts comment is spot on—my living room looked like a kindergarten project gone wrong after my first window attempt. I had tape stuck to my jeans, the dog, you name it. I also fell into the “seal every gap or else” trap, then spent a week wondering why I suddenly had a mini rainforest on my sills. It’s wild how all those pro videos make it seem like a science, but then your 1940s house throws you curveballs. The moment I eased up on the foam and let the window breathe a bit, the condensation actually chilled out. Go figure.
I haven’t tried the rigid pans, but I almost bought one when I saw them at the store. The price made me pause—looked sturdy, but I couldn’t figure out how I’d get it to fit my not-even-close-to-square opening without a grinder or something. Plus, I kept picturing myself slicing a finger off trying to shim it in. Flexible pans sounded easier until I realized my idea of “flexible” and the manufacturer’s are not the same. Tape felt like the lesser evil, even if it’s a pain to get right.
One thing I did differently on my last window was using backer rod for most gaps and just a little foam at the corners. That seemed to help with drafts and didn’t trap as much moisture. Might just be luck, but it beat having to mop up every morning.
I’m convinced there’s no one-size-fits-all for these old houses. Every fix is a bit of a gamble... sometimes you win, sometimes you get a new science experiment on your windowsill. If someone invents that magic all-in-one product, I’ll be first in line, wallet ready. Until then, guess I’ll keep treating window installs like a weird hobby I never meant to have.
Every fix is a bit of a gamble... sometimes you win, sometimes you get a new science experiment on your windowsill.
This cracked me up because I swear my first window job turned into a full-on biology lesson with all the weird stuff growing in the corners. I tried those “flexible” pans too—ended up looking like a crumpled lunch tray and still didn’t fit. I’ve had the best luck just taking it slow, measuring three times, and being okay if things aren’t perfect. Old houses definitely have their own rules.
Totally get the science experiment thing—my second window job, I found this weird orange fuzz in the sill that looked like it belonged in a petri dish. Old houses really do have their own logic. I’ve tried to follow all the “rules” from YouTube tutorials, but honestly, half of them assume your house is perfectly square. In reality, I ended up shimming one side so much it felt like building a Jenga tower. Not perfect, but at least it keeps the rain out... for now.
That orange fuzz is no joke—pretty sure I’ve found every color of mold under the sun in my sills. The tutorials always make it look like you’re working with a brand-new build, but when your window opening is more parallelogram than rectangle, those “just shim it until it’s level” instructions get old fast. I had to use so many shims on one side I started worrying about structural integrity... but hey, at least the draft is gone (for now). Old houses definitely keep you humble.
“just shim it until it’s level” instructions get old fast. I had to use so many shims on one side I started worrying about structural integrity...
I know what you mean with the shims, but I’ve actually found that sometimes less is more—if you’re stacking too many, it might be worth pulling the window and trimming the framing a bit, even if it feels drastic. I tried packing in a bunch once and ended up with a weird creak every time the wind blew. Not sure if anyone else has tried planing or sistering the studs instead? It’s messier, but felt sturdier in my 1920s place.
I’ve definitely been guilty of the “shim stack” approach and yeah, it always feels sketchy once you get past three or four. Pulled one out once and the whole window shifted—lesson learned. Trimming the framing is messy, but honestly, it’s usually worth it.