I’ve had both on my roof—old-school felt on the garage, synthetic on the house. We get some nasty wind here (Midwest, open fields), and honestly, the synthetic held up better last spring when we had those 60+ mph gusts. The felt underlayment on the garage peeled back at the edges where it wasn’t nailed down perfectly, but the synthetic stayed put. I think it’s partly because it’s lighter and doesn’t absorb water, so it doesn’t get heavy and saggy after a storm.
That said, if the crew is sloppy with either one, you’re still in trouble. I watched them install mine and made sure they overlapped everything right—probably annoyed them, but hey, it’s my roof. The only downside I’ve noticed with synthetic is it can be slippery to walk on if there’s dew or frost, so heads up if you’re doing any work yourself.
Not saying synthetic is magic, but for wind and rain, I’d pick it again over felt. Just make sure whoever installs it actually cares about the details...
- Totally agree on synthetic outperforming felt in wind. Seen too many felt jobs fail at the seams or edges, especially if installers skip fasteners or overlap.
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Couldn’t be more true. Even the best material won’t save you from a rushed install.“if the crew is sloppy with either one, you’re still in trouble.”
- One thing I’d add: some synthetics have UV exposure limits—watch out if your shingles get delayed. Had a client leave it exposed for 3 months and it started to degrade.
- The slip factor is real. I’ve nearly gone off a roof before sunrise because of frost on synthetic. Not fun.
- For storm-prone zones, synthetic’s lighter weight and water resistance are huge pluses. Just double-check manufacturer specs—some brands are tougher than others.
That UV thing is wild—I didn’t even know some synthetics could start breaking down that quick. Is there a brand that actually holds up longer if you get stuck waiting on shingles? I’ve seen guys just throw tarps over it, but that seems sketchy.
I’ve actually run into this a few times after hurricanes—synthetic underlayment is supposed to last, but some brands really do start curling or getting brittle in just a couple weeks of direct sun. I remember one job where we used a higher-end synthetic (can’t recall the exact brand, maybe Titanium?) and it held up for about two months before the shingles finally arrived. Tarps just don’t cut it long-term; wind gets under them and you’re dealing with leaks or worse. Still, nothing’s bulletproof if you’re waiting months, especially in the southern sun. Has anyone had luck with those newer self-adhering membranes? I’m curious if they actually outlast the standard synthetics.
Self-adhering membranes are kind of a mixed bag in my experience. They’re definitely tougher than the basic synthetics—especially if you’re stuck waiting weeks for shingles—but I wouldn’t call them a magic bullet. Here’s what I’ve seen work (and not work):
1. Prep is everything. If the deck isn’t clean and dry, those membranes can bubble or peel, especially after a heavy rain. Seen it happen more than once.
2. The higher-end brands (like Grace Ice & Water Shield) do hold up better under sun and wind, but even they start to degrade after a couple months of direct exposure. Southern heat just cooks everything eventually.
3. They’re heavier and pricier than synthetics, so if you’re covering a big roof, costs add up fast.
One thing I’ll say: they seal around nails way better than standard underlayment, so leaks are less likely if you get a pop-up storm. But if you’re looking for something that’ll last all summer uncovered, I haven’t found anything that truly does the trick yet. Maybe metal panels as a temp cover, but that’s a whole other headache...
