I’ve noticed the UV thing too—some of that “60-day exposure” marketing seems a bit optimistic, especially in July. I had a patch of synthetic that started getting brittle after just three weeks under direct sun. Out of curiosity, has anyone had issues with synthetics sticking to sheathing during hot spells? I’ve seen it once or twice, and getting it up without shredding was... not fun. Wondering if certain brands are worse for that, or if it’s just the Midwest heat doing its thing.
I’ve had the same thing happen with synthetic underlayment getting kind of tacky and sticking to the sheathing, especially during those crazy hot stretches. I’m in central Illinois, so the Midwest heat is definitely a factor. The first time it happened, I thought maybe we’d left it exposed too long, but it was only about two weeks. It peeled up in strips and left a mess behind—definitely not what I expected after all the “extended exposure” claims.
I tried switching brands after that (went from a big box store’s house brand to one of the pricier ones) and honestly, didn’t notice a huge difference. Both got a little brittle and sticky if they sat out in direct sun for more than a couple weeks. Maybe some brands are slightly better, but I think the heat just cooks everything eventually.
If you’re stuck waiting on shingles or something, I’d say try to keep it covered as much as possible or at least get it nailed down tight so it doesn’t bubble up and bake. Not a perfect fix, but it helped me avoid another sticky mess last summer.
Had a similar headache last July—roofers left the synthetic underlayment exposed for about ten days, and it basically melted onto the OSB. I’ve tried three brands now, and honestly, none of them seem to handle Midwest sun that well. I’m starting to think those “30-day exposure” claims are just marketing fluff. At this point, I just budget extra time to get shingles on ASAP... learned that lesson the hard way.
I’m starting to think those “30-day exposure” claims are just marketing fluff.
Yeah, I’ve been burned by those claims too. What’s worked for me is to break the job into smaller sections—only tear off as much as you can shingle that day. I know it slows things down, but it’s saved me from having to replace underlayment that got baked onto the sheathing. Also, if you’re pinching pennies like me, keep some rolls of felt around as backup. It’s not perfect, but at least it doesn’t weld itself to the OSB in a heatwave.
it doesn’t weld itself to the OSB in a heatwave.
That’s exactly what happened to me last summer. I used a “premium” synthetic underlayment that claimed 60-day exposure, but after just two weeks of 90-degree days, it fused to the sheathing and tore up in strips when I tried to fix a section. Ended up switching back to felt for the rest—less durable, but at least it comes off clean. I get why people break the job into sections, but with my steep roof, even that was a hassle. Sometimes the old-school stuff just works better, even if it’s not as flashy.