I've messed around with marine-grade silicone before—used it on a skylight flashing a couple winters back. Honestly, it held up better than the regular stuff, but after about two seasons of freeze-thaw cycles, it started peeling at the edges. Maybe I didn't prep the surface perfectly, who knows... but aluminum flashing expands and contracts quite a bit with temperature swings, and silicone—even marine-grade—isn't really designed to handle that kind of constant movement.
Ended up redoing it properly with some aluminum-backed flashing tape (the kind roofers use). It was a bit pricier and took more effort upfront, but it's been rock solid ever since. No leaks, no peeling edges. If you're looking for a quick fix, silicone might buy you some time, but if you want peace of mind long-term, I'd bite the bullet and redo it right.
"Ended up redoing it properly with some aluminum-backed flashing tape (the kind roofers use). It was a bit pricier and took more effort upfront, but it's been rock solid ever since."
Interesting you mention the flashing tape—I just went through something similar myself. When I bought my place last year, I noticed the flashing around the chimney looked pretty sketchy. Being new to homeownership, I initially thought silicone would do the trick (seemed quick and easy enough, right?). But after reading up a bit, I realized silicone probably wouldn't handle the constant expansion and contraction of aluminum.
I ended up going with that same aluminum-backed tape you mentioned. Took me a while to prep everything—cleaning off old sealant residue was a pain—but once it was on there, it felt super secure. It's only been one winter so far, but no leaks yet... fingers crossed. Curious though: did you have any trouble getting the tape to stick properly? Mine kept bunching up at first until I got the hang of applying it smoothly.
Yeah, silicone and aluminum flashing are definitely not best friends. Learned that the hard way myself a few years back when I tried a quick fix after a nasty storm. Thought I'd save myself some hassle by just slapping on some silicone caulk around the edges—seemed logical at the time, right? Well, it lasted maybe two months before it started peeling away and leaking again. Lesson learned.
Anyway, I switched to the aluminum-backed flashing tape too, and it's been solid ever since. But man, you're not kidding about getting it to stick smoothly. My first attempt looked like a crumpled candy wrapper—bubbles and wrinkles everywhere. I found out pretty quickly that temperature makes a huge difference. If it's too cold, the adhesive gets stiff and won't bond properly; too hot, and it turns into a sticky mess that's impossible to handle. I ended up waiting for a mild day (around 60-70°F) and used a small roller to press it down as I went along. That helped a ton.
Also, prepping the surface was key. Like you said, cleaning off old sealant residue is a royal pain, but totally worth it. I used some rubbing alcohol after scraping off the old stuff—it really helped the tape adhere better. It's been through two winters now with no leaks or lifting edges yet... knock on wood.
One thing I'm curious about though: did you guys put anything extra over the tape afterward? I've heard mixed opinions—some folks swear by coating it with roofing sealant or paint for extra protection, while others say it's unnecessary. I haven't done anything extra yet, but I'm always open to suggestions if it'll help avoid another round of repairs down the road.
Interesting points, but honestly I've had pretty good luck with silicone and aluminum flashing—though it wasn't exactly a quick slap-on job. I learned from an old roofer friend that the trick is using neutral-cure silicone instead of the standard stuff from the hardware store. Apparently, regular silicone releases acetic acid as it cures, which reacts badly with aluminum and causes it to peel off pretty quickly (sounds like what happened to you). Neutral-cure silicone doesn't have that issue.
I used it on my shed roof about four years ago after a similar storm fiasco. Took my time prepping the surface—scraped, cleaned with alcohol, all that jazz—and applied a nice bead of neutral-cure silicone around the flashing edges. It's held up surprisingly well so far, even through some nasty winters.
Never tried the aluminum-backed tape myself... seems like a solid solution too, though I do wonder if adding another layer on top might trap moisture underneath? Might be overthinking it, but I've always been cautious about layering sealants or coatings without giving moisture somewhere to escape. Just my two cents anyway.
Neutral-cure silicone is definitely a game changer—wish I'd known about it sooner. I had a similar issue with aluminum flashing peeling off after using regular silicone. Thought I was being clever by sealing everything up tight, but nope... learned the hard way about that acetic acid reaction you mentioned.
Funny enough, I ended up going with aluminum-backed tape as a quick fix (mostly out of frustration and impatience). It actually held up better than expected, but you're right about moisture concerns. After a year or so, I noticed some bubbling underneath, probably trapped water. Eventually bit the bullet, stripped it all down, and redid it properly with neutral-cure silicone and careful prep. Been solid ever since.
Lesson learned: shortcuts usually aren't. But hey, at least my roof got some extra attention... twice.
