I’ve wondered about the hemp stuff too—seems like a cool idea, but I’d be worried about mold or breakdown in humid summers. I used synthetic on my last shed project and it was way easier to handle than felt, but I still taped every seam and overlapped more than the minimum. Insurance here (Midwest) was the same story: they only covered basic felt unless I could show city code required synthetic. Kind of frustrating, honestly.
- I’ve had similar headaches with insurance only wanting to cover felt, even though synthetic seems to be the go-to for a lot of contractors now. Midwest humidity is no joke, and I’ve seen felt start to curl or even get a little funky-smelling if it gets wet before shingles go on.
- From what I’ve seen on our properties:
- Felt is cheaper, but it really doesn’t like sitting exposed. If you get a week of rain before the roofers finish, it can wrinkle or tear.
- Synthetic is lighter, easier to roll out, and holds up better if the job gets delayed. I’ve had crews leave it exposed for a couple weeks with no issues.
- Mold-wise, synthetic seems less likely to have problems, but if water gets trapped underneath, anything can get gross over time.
- Hemp is interesting, but I’d be nervous about long-term durability unless you’re in a super dry climate. Haven’t seen it used around here, probably for that reason.
- On a couple of our older buildings, we had felt underlayment from the 90s. It held up, but there were spots where leaks started at seams that weren’t overlapped enough. The newer synthetics we’ve used haven’t had that issue yet, but they’re only about 7-8 years old, so hard to say if they’ll last as long.
- For insurance, I’ve had luck getting synthetic covered if I could show a contractor’s recommendation in writing, not just city code. Sometimes it’s just about who you talk to on the phone...
- If you’re DIY-ing, synthetic is way easier to handle, especially on steeper roofs. Less slipping, less tearing, and you don’t end up covered in black dust.
- Only downside I’ve seen is synthetic can be a little more slippery when wet, so if you’re up there, be careful.
- Personally, I’d go synthetic again, but I get the frustration with insurance. The extra cost upfront has saved me a couple headaches down the line, especially with unpredictable Midwest weather.
Had a real “learning experience” with felt after a summer storm hit before the shingles went on—came back to what looked (and smelled) like a compost pile up there. Synthetic’s been a lot less dramatic for me, especially with how fast weather turns around here. Only gripe is it feels like you’re ice skating if there’s dew in the morning, but I’ll take that over wrestling soggy felt any day. Still waiting to see if synthetic holds up past the 10-year mark, though...
Had a similar situation with felt a few years back—left it on for just a weekend and a pop-up storm turned it into mush. The smell was something else... Ended up costing more to replace the ruined stuff than if I’d just gone synthetic from the start. That said, I’m still not totally sold on synthetic’s long-term durability either. It’s holding up so far (about 6 years in), but I do wonder if it’ll start breaking down before I’m ready to re-roof. At least it doesn’t turn into a slip-n-slide every time it rains, though.
At least it doesn’t turn into a slip-n-slide every time it rains, though.
That’s been my experience too—felt just gets nasty if it’s exposed to any real moisture. I had a section left uncovered for a couple days during a remodel, and it basically disintegrated. The synthetic stuff I used after that was way easier to walk on, even when wet, which made a huge difference safety-wise.
Long-term, I’m in the same boat as you—mine’s about 8 years old now under asphalt shingles, and it still looks fine from what I can see in the attic. I do wonder about UV exposure if it’s left uncovered for too long, but as long as it’s protected by shingles, I haven’t seen any signs of breakdown yet.
One thing I noticed: synthetic is a lot lighter and easier to handle, but it can be a pain to get it to lay flat on windy days. Still, I’d take that over the mess of soggy felt any day. Curious if anyone’s actually had synthetic fail before the roof needed replacing? Haven’t heard of it yet, but maybe it’s just not old enough in most cases.