Pulled up a 12-year-old roof last summer—south-facing, brutal Texas sun. The “high-temp” synthetic underneath was still flexible, but you could tell it had started to lose some strength, especially around the nail holes. Not as bad as the cheaper synthetics I’ve seen, but definitely not bulletproof. I still trust a good #30 felt for longevity, even if it’s a pain to work with.
I get where you’re coming from about the #30 felt, but I’ve had a different experience with it—especially in hot, humid weather. We replaced my parents’ old roof maybe 8 or 9 years ago (asphalt shingles, southeast Texas, so plenty of heat and storms). Used #30 felt because that’s what my dad swore by. But man, the stuff was already brittle in some spots when we pulled the shingles off. It tore pretty easily around the fasteners and just didn’t seem to have much fight left in it. Maybe it’s changed over the years? Or maybe it was just sitting too long before install, hard to say.
On my own place, I went with a mid-grade synthetic (not the cheapest roll at the store, but not “premium” either). After a few hurricanes and a couple of those wild spring hailstorms, I checked under some lifted shingles last year out of curiosity. The synthetic still looked decent—no crumbling or cracking at least. It *did* have some wear around nail holes like you mentioned, but nothing too scary yet.
One thing I noticed: walking on felt during install in Texas heat is a nightmare. Stuff gets slippery or starts sticking to your boots if it’s hot enough. The synthetic was way easier for me and my knees.
Not saying synthetics are perfect—seen some really thin ones that might as well be plastic wrap—but I’m not sure felt is automatically tougher anymore. Maybe if you get the old-school heavy stuff, but that’s getting harder to find around here.
Curious if anyone’s actually had underlayment last more than 15 years in full sun? Feels like everything has its limits once you throw Texas weather at it...
I’ve pulled up a few roofs in central Texas and southern Oklahoma, and honestly, I haven’t seen underlayment—felt or synthetic—hold up more than 15 years in direct sun. The old #30 felt from decades ago did seem heavier and maybe lasted a bit longer, but the newer stuff just doesn’t have the same guts. Like you said, it gets brittle and tears up around fasteners, especially after baking under shingles for years.
The synthetics are hit or miss. Some of the cheap ones feel like tissue paper, but mid-grade or better seems to hold up surprisingly well, at least for now. I put synthetic down on my garage roof about 10 years back; after a couple of windstorms and some gnarly hail, it’s still flexible where I’ve checked under loose shingles. No cracking yet, which is more than I can say for the felt on my main house.
Walking on felt in Texas heat is no joke. I’ve nearly slid off a few times—synthetic definitely has the edge there. But yeah, nothing seems bulletproof once you factor in our weather. If anyone’s had something last past 15 years in full sun here, I’d be impressed... but I’m not holding my breath.