I get what you’re saying about the shingle overlap, but honestly, I’ve seen more issues crop up from the actual fasteners than from the flashing itself—especially with solar attic fans. Last summer, I helped a neighbor install one on his composite shingle roof. We were super careful with the flashing, but a couple of those self-tapping screws ended up just a hair off and that’s where water found its way in after a big storm. The weird part? The flashing looked perfect from above, but underneath, there was just enough of a gap for capillary action to do its thing.
I’m not totally convinced it’s always about movement from temp swings either. Composite shingles can flex a bit, sure, but if you use the right sealant and don’t overdrive the fasteners, things usually stay put. Metal roofs are another story—those expand and contract like crazy and can pull things loose over time. But with composite, I’d double-check every screw and maybe even go for a butyl tape under the flashing next time. It’s not foolproof, but it’s saved me some headaches.
That’s wild, I’ve seen something similar happen with a ridge vent install—flashing looked textbook, but a couple screws weren’t snug enough and water tracked right down the threads. I started using a dab of high-grade sealant under each fastener and it’s made a difference. Butyl tape under flashing is a solid call too, especially on older shingles where things don’t always sit flush. It’s funny how the little details end up being the big headaches...
It’s funny how the little details end up being the big headaches...
That’s the truth. I thought I was being super careful with my attic fan install, but I still ended up chasing a tiny drip for weeks. My shingles are about 18 years old and definitely not as flat as they used to be, so getting everything to sit right was a pain. Did you notice any issues with the sealant holding up over time, especially through freeze/thaw cycles? I’m in the Midwest and that seems to be where things start to fail for me.
My shingles are about 18 years old and definitely not as flat as they used to be, so getting everything to sit right was a pain.
Man, I hear you on that. Once those shingles start curling up, it’s like trying to get a sticker to stick to a basketball. Midwest freeze/thaw is brutal—sealant always seems fine until that first spring melt. I’ve had better luck with butyl tape under the flashing, then a bead of high-quality polyurethane sealant on top. Still, nothing’s perfect if the shingles are waving at you in the wind...
Getting a solar attic fan on 18-year-old shingles is always a bit of a wrestling match. Once those tabs start curling, nothing wants to lay as flat as the instructions suggest. I’ve run into that plenty—sometimes you peel up a shingle and it just cracks or crumbles in your hand. Midwest winters don’t do us any favors either.
Butyl tape under the flashing is a good move, and that polyurethane bead helps, but honestly, if the shingles are waving at you, there’s only so much sealant can do. I’ve had jobs where I ended up sliding an extra piece of aluminum step flashing under the problem area, just for peace of mind. Not always pretty, but it keeps the water out.
If you’re not seeing leaks after the first couple of storms, you probably did better than most. Just keep an eye on it when the snow melts—those old shingles can surprise you with new gaps once everything thaws out. Sometimes it’s more about managing what you’ve got than making it perfect.
