That’s a fair point about the longevity of felt. I’ve been surprised at how well some of the older underlayments have held up, especially when you factor in the storms. Synthetic’s lighter and easier to install, but I’ve seen a few cases where it didn’t handle UV exposure as well as advertised. The environmental side is tricky too—felt’s not exactly “green,” but at least it breaks down faster than plastic. I guess it really depends on the roof, climate, and how long you expect it to last... there’s no one-size-fits-all answer.
“I’ve seen a few cases where it didn’t handle UV exposure as well as advertised.”
Yeah, that’s been my experience too. The lighter weight of synthetics is great for big jobs, but if the shingles get delayed and that stuff bakes in the sun, it can get brittle or even tear. Felt’s not perfect, but I’ve torn off 20-year-old roofs where the old 30# was still hanging in there, even after a few hurricanes. But man, it’s heavy and a pain to haul up a steep pitch. Around here (humid, lots of storms), I usually tell folks to think about how long they want the roof to last—and how much patience they’ve got for repairs down the road. No magic bullet, just trade-offs.
I’ve noticed the same thing with synthetics—on paper they sound like they’ll outlast everything, but in practice it’s a mixed bag. Last summer I helped on a reroof where the synthetic was left exposed for maybe two weeks (scheduling got weird with all the rain). By the time we finally started laying shingles, the stuff had faded and felt almost crunchy in spots. We had to patch a couple tears near the ridge where it just couldn’t handle the wind. I get why folks like it, though. Dragging rolls of 30# up a 10/12 pitch is a workout I don’t miss.
But I’ve also seen old felt that basically turned to dust when we pulled the shingles off. Maybe it’s the brand or just how long it sat, but it definitely doesn’t always hold up forever. Around here (mid-Atlantic, lots of humidity and freeze/thaw), the roofers I work with seem split. Some swear by synthetic for the weight and grip, others stick to felt because it’s what they trust when jobs get delayed.
One thing I will say—synthetic is way less miserable to install on a hot day. It doesn’t stick to your boots or your arms like felt does. But if you’re not getting shingles on right away, I’d be nervous leaving it exposed for more than a week or two, no matter what the packaging says. Maybe in a dry climate it’d be different?
Anyway, both have their headaches. I’m still figuring out what I like best, but I haven’t found anything that’s truly “set it and forget it.” Seems like with underlayment, you’re always trading one hassle for another.
That’s pretty much been my experience too—synthetics sound great until you actually have to trust them through a couple weeks of weird weather. I had a section of my roof redone last fall (asphalt shingles, 7/12 pitch, Maryland suburbs), and the crew used synthetic underlayment. Looked sharp at first, but we got hit with a few days of wind and drizzle before the shingles went on. I noticed some spots near the eaves where it started to curl up and even a small tear around a nail head. The foreman said it was “within spec,” but I couldn’t help wondering how much water actually got through.
I’m curious if anyone’s seen a difference between brands? The stuff they used on mine was supposed to be “premium,” but it didn’t seem much tougher than the generic rolls I’ve seen at Home Depot. Maybe it’s just marketing hype.
On the flip side, I remember helping my neighbor strip his old roof (probably 25 years old, 3-tab shingles, original felt underneath). That felt was basically confetti—just crumbled in your hands. But then again, it did its job for two decades, so maybe that’s all you can ask for.
One thing I keep coming back to: does anyone actually trust the “60-day exposure” claims on synthetic packaging? I get nervous leaving anything uncovered for more than a week, especially with our humidity swings and random storms. Is that just a best-case scenario in perfect weather, or has someone actually seen it hold up that long?
I guess at the end of the day, it’s always a gamble. You pick your poison—lighter rolls and easier install with synthetic, or the old-school reliability (sort of) with felt. Has anyone tried those hybrid underlayments that claim to combine both? Or is that just another gimmick?