I get where you’re coming from with the metal flashing and mechanical fasteners—definitely the safest bet for Midwest weather. But I’ll admit, I went with one of those newer synthetic flashing kits (the kind with the butyl adhesive and flexible membrane) on my garage roof last year. It’s a low slope, and I was honestly just tired of wrestling with sheet metal up there.
So far, it’s held up through a couple of pretty wild storms and a freeze-thaw cycle. No leaks yet, and it was way easier to get a tight seal around the odd angles. I did make sure to prep the surface really well and used extra fasteners at the edges, just in case. Maybe it’s not as bulletproof as custom-bent metal, but for smaller jobs or less exposed spots, I think the new synthetics are worth considering.
That said, I wouldn’t trust them on the main house roof or anywhere that gets hammered by wind. For those spots, yeah, metal all the way. Just figured I’d throw out a different experience—sometimes the “easy” option isn’t always temporary, depending on where and how you use it.
Maybe it’s not as bulletproof as custom-bent metal, but for smaller jobs or less exposed spots, I think the new synthetics are worth considering.
That’s a fair point—those butyl-based membranes have come a long way. Did you notice any issues with adhesion in the cold, or did it stick right away? I’ve seen a few cases where folks didn’t prep the surface enough and got some sneaky leaks months later. Sounds like you were pretty thorough, though. Curious if you checked under the membrane after that first big storm, or just trusted the “no drips” test? Sometimes I wish all roofs were as forgiving as a garage...
Curious if you checked under the membrane after that first big storm, or just trusted the “no drips” test?
I’ll admit, I’m a “trust but verify” type—especially after seeing what a surprise leak can do to attic insulation. After my last install, I actually popped a shingle and peeled back a corner just to make sure everything was bone dry. Maybe overkill, but I’ve seen too many jobs where folks just cross their fingers and hope for the best.
Those butyl membranes are definitely better than they used to be, but cold weather is still tricky. If it’s below 40°F, I’ll hit the surface with a heat gun or even just leave a tarp over it until the sun warms things up. Otherwise, you get that “sorta stuck” feeling, and months later—bam, water stains.
Honestly, nothing beats custom metal for peace of mind, but for a quick attic fan or a vent pipe, synthetics are a decent compromise. Just gotta prep like you’re painting a classic car, not slapping on a bumper sticker.
I’m with you on the “trust but verify” approach—seen way too many attic fans installed with just a bead of caulk and crossed fingers. I’ve actually found water tracking sideways under membranes after a wind-driven rain, even when everything looked fine from inside. Out of curiosity, do you ever see issues with ice damming around those synthetic membranes in colder climates? I’ve noticed some brands claim to self-seal, but I’m not convinced they’re all equal once temps drop.
I’ve noticed some brands claim to self-seal, but I’m not convinced they’re all equal once temps drop.
Yeah, I hear you on that. The “self-sealing” thing always sounds great on the packaging, but in real-world cold snaps, I’ve seen those membranes get stiff and not bond as well as advertised. Especially up here in the Midwest, where we get those freeze-thaw cycles—sometimes you’ll see a little ice dam form right at the edge of the membrane, and water finds its way in under the shingles anyway.
I’ve also noticed that some of the cheaper synthetics don’t seem to seal around nails as well when it’s below freezing. You poke a fastener through and it just kind of stays open, which isn’t ideal if you’re counting on that as your last line of defense.
Honestly, I still trust a good old-fashioned ice & water shield more than some of these newer synthetics, at least for the first few feet up from the eaves. Maybe I’m just old school, but I’d rather overdo it than risk a call-back in February when everything’s frozen solid.
