Good tips above, silicone can be a real pain sometimes. I've found that even when you prep perfectly, silicone still isn't always the best choice for windows—it's flexible but doesn't always bond as well as you'd hope to certain surfaces. For me, a high-quality polyurethane-based caulk has been way more reliable. It sticks better, stays flexible enough for seasonal shifts, and doesn't seem to break down as quickly.
Weather stripping is great too if you've got noticeable gaps or drafts, but if it's rain sneaking in around the frame itself, caulk usually does the trick better. Just make sure you don't rush the drying time—learned that lesson myself after spending a rainy afternoon redoing a window I'd sealed too soon. Nothing like watching your hard work turn into a soggy mess...
Good points on polyurethane—definitely bonds better in my experience too. Curious though, anyone tried hybrid caulks (polymer blends)? I've heard they're flexible and stick well, but haven't tested them myself yet...
I've recently used a hybrid polymer blend around my patio door, and so far it's held up really well through some heavy rains. Application was straightforward, and flexibility seems promising. Might be worth giving it a shot if you're curious...
Hybrid polymer blends are cool and all, but honestly, I've had better luck with good old-fashioned weather stripping for windows. Maybe it's just me being a newbie homeowner and all thumbs, but applying caulk or polymer neatly is trickier than it sounds—my patio door looks like a kindergartner did arts and crafts day. Weather stripping took less effort, sealed tight, and I didn't have to worry about making a mess...or accidentally sealing the window shut (true story, sadly).
Weather stripping's definitely easier if you're new to DIY, but honestly, caulk or polymer done right will outlast it by a mile. Trick is to tape off the edges first—makes cleanup a breeze and keeps your windows from looking like a preschool art project (been there myself...). Plus, weather stripping eventually wears down and you'll be redoing it sooner than you think. Just my two cents, but a little practice with caulk goes a long way.
Good points about caulking, especially the taping trick—definitely saves headaches. But I'd argue weather stripping still has its place, particularly if your window frames have some movement or shifting. Caulk is great for sealing stationary gaps, but it doesn't handle movement well. I've seen plenty of caulk jobs crack prematurely because the homeowner didn't account for seasonal expansion and contraction.
Weather stripping, on the other hand, is designed specifically to accommodate that kind of movement. Sure, it wears out eventually, but replacing it every few years isn't a huge hassle, especially considering it's inexpensive and quick to install. I've had clients who tried caulking windows in older homes, only to find themselves redoing it sooner than expected because of shifting frames.
Bottom line, both methods have their strengths—just depends on your specific situation and how much movement you're dealing with around those windows.
Good explanation on the seasonal movement issue—seen that plenty myself. One thing I'd add is that sometimes combining both methods works wonders. Caulk the stationary seams first, then weather strip the parts prone to shifting. Have you tried a combo approach yet?
Good point about combining methods—I've seen that work nicely, especially in older homes where things shift around a bit. One tip: when you're weather stripping the moving parts, make sure to leave just enough room for smooth operation. Ever run into issues with windows sticking after sealing?
I've actually had the opposite issue—left a bit too much space to avoid sticking, and ended up with drafts sneaking in. It's a tricky balance... especially with older windows that have their own quirks. Sometimes trial and error is the only way to get it right.
Have you considered that maybe it's not just about spacing? Older windows often warp slightly or shift over time, so even if you get the spacing perfect initially, it might change later. I get the trial and error thing, but maybe the issue isn't just how much space you leave—could it be the material you're using? I've found that sometimes caulk can be too rigid for windows that shift seasonally, causing gaps to reopen or drafts to sneak back in. Weather stripping, especially the foam tape kind, has a bit more give and can adapt better to slight movements.
Also, have you checked if your window frames are still square? I had an older house once where the frames had warped slightly, and no amount of caulk or stripping would fix it until I addressed the alignment itself. It was a pain, but shimming and adjusting the frame made a huge difference. Maybe worth looking into before you spend more time on spacing alone?
Just throwing it out there...