Things you wish you knew before installing new windows

I’ve installed a ton of windows over the years, and honestly, the biggest thing I wish I’d paid more attention to early on was flashing and sealing. It’s not glamorous, but if you don’t get that right, you’ll be fighting leaks forever—especially if your house is older or the walls aren’t perfectly square (which is most of them, in my experience). I’ve had decent luck with Tyvek FlexWrap and good quality silicone caulk, but I know some folks swear by other brands.

One thing that tripped me up my first couple times was not dry-fitting the window before running beads of sealant. Seems obvious, but sometimes the opening’s just a hair off and you end up with a mess. Also, don’t over-tighten the screws—vinyl windows especially can warp if you crank them down too much.

For tools, a good level (longer the better) and shims are your best friends. I’ve tried to “eyeball” it before and regretted it every time. Anyone else ever have a window that looked straight until you stood across the room?

That’s funny, I thought I could get away with a short level once—big mistake. The window looked fine up close, but from across the living room it was way off. I’ve also had mixed results with different flashing tapes, especially in cold weather when they just don’t want to stick. Ever try any of the liquid-applied flashing stuff? I’m curious if it’s actually easier or just another mess to clean up.

Man, I hear you on the short level—been there, done that, ended up with a window that looked like it was trying to escape. As for the flashing tape, cold weather is the worst. I tried liquid-applied flashing once and honestly, it was less of a sticky mess but more of a “did I just paint my house by accident?” situation. Still, I think it sealed better than the tape ever did in winter. Don’t beat yourself up—windows have a way of humbling even the most confident DIYer.

That “window trying to escape” image is way too real—I swear my kitchen one still has a slight lean, but I tell myself it’s “character.” Liquid flashing sounds less sticky, but I’d probably end up with it all over my clothes (and the dog). I tried tape in November and learned it hates cold as much as I do. If I ever do this again, I’m waiting for spring… or hiring someone who actually knows what they’re doing.

I totally get the “lean” thing—my living room window has a tilt that drives me nuts, but apparently it’s “vintage charm.” I tried liquid flashing too and wow, it’s messier than I expected. As for tape, I learned the hard way that cold weather just makes it peel right off. Do you think waiting for warmer temps really makes that much difference with adhesives? I keep wondering if there’s a trick to making it stick in winter, or if I’m just fighting nature.

I’ve heard that too about adhesives and cold weather, but honestly, I’m not convinced it’s always a dealbreaker. I tried using a hair dryer to warm the tape and the frame, and it actually stuck way better than before. Maybe it’s just about getting creative with the tools you have? The mess from liquid flashing, though… haven’t figured out a workaround for that yet.

- Totally agree on the tape and cold weather thing. I’ve had mixed results—sometimes it just needs a bit of help like you said.
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“I tried using a hair dryer to warm the tape and the frame, and it actually stuck way better than before.”

I’ve done something similar with a heat gun (very carefully). Makes a noticeable difference, but you gotta watch for overheating.
- Liquid flashing is always messy for me too. I found using painter’s tape along the edges helps keep cleanup manageable, but it’s still not perfect. Tried a couple brands—some are definitely less runny than others.
- One thing I wish I’d known: how much temperature and humidity can mess with curing times. Had one window where the flashing stayed tacky way longer than the label said. Not fun.