- Seen a lot of felt underlayment during inspections, and honestly, it’s usually the first thing to go when there’s a leak.
- Synthetic holds up way better, especially in places where you get wild temperature swings. Midwest winters are brutal on roofs—felt just can’t keep up with all that expanding and contracting.
- That said, I’ve come across some older homes where the original felt is still hanging in there after 15+ years… but usually that’s paired with a steep pitch and good attic ventilation. Not exactly the norm.
- For sheds or quick fixes? Sure, felt’s cheap and easy to slap down. But if you’re hoping not to crawl up there again for a decade or two, synthetic’s the safer bet.
- One thing I’ve noticed—synthetic can get slippery when wet. Nearly took a tumble last spring checking out a new build. So, if you’re DIY-ing, watch your step...
- Price difference isn’t huge anymore either, at least around here. For most folks, it just makes sense to go synthetic unless you’re really pinching pennies or working on something temporary.
- Walked a roof last month where the felt was basically confetti under the shingles—guess who got to explain that to the homeowner? Not my favorite conversation.
- Synthetic’s been holding up better in my area, too. I’ve seen some of it look almost brand new after 10 years, even with our freeze-thaw circus every spring.
- That said, I did run into one old-timer who swore by his original felt from the ‘90s. Steep roof, attic like a wind tunnel, and not a hint of rot. Outlier for sure, but it happens.
- Slippery synthetic is no joke... nearly did the splits last fall when some dew hit before I got up there. Felt might rip, but at least it’s not trying to send you off the edge.
- Honestly, if we’re racing these things, felt’s pulling a hamstring halfway through unless it gets ideal conditions and a little luck. Synthetic’s just jogging along steady, maybe tripping here and there but still finishing strong.
I hear you on the synthetic being slick—nearly skated off a 10/12 myself last spring. Still, I’ve seen some of the newer “grippy” synthetics do a lot better, especially when the dew hits. For longevity though, I’d put my money on synthetic unless you’re in some weird microclimate where felt just happens to thrive. Every time I’ve torn off a roof in our wet winters, felt’s usually toast unless it got lucky with perfect ventilation.
I’ve seen a lot of roofs in all kinds of shape, and honestly, I’m still not totally sold on the “synthetic always wins” idea. Sure, the newer synthetics are way tougher than the old tar paper, and they do hold up better when you’re dealing with months of rain or snow sitting on a half-done roof. But I’ve also come across some jobs where the synthetic was curling at the edges after just a few years—usually when it wasn’t fastened right or got too much sun before shingles went on.
Felt’s definitely more fragile, but I’ve pulled up 30-year-old felt that looked surprisingly okay under heavy tile, just because the attic had perfect airflow and no leaks. That’s rare, though. Most times, like you said, it’s mushy or torn to bits.
If I had to bet on which one would limp across the finish line last, I’d probably still pick synthetic—just not by as much as folks think. But if you’re in a spot with wild temperature swings or a lot of UV exposure, nothing lasts forever. Sometimes it feels like we’re just picking which headache we want down the road...
I get where you’re coming from, but I actually went with felt when I replaced my roof last year—mostly because my neighbor’s synthetic underlayment started peeling up after a couple of hot summers. The roofer said it was probably installed too early and baked in the sun, but it still made me nervous. I figure if the attic’s got good ventilation and you’re not dealing with constant leaks, felt can hang in there longer than folks expect. Not saying it’s perfect, but sometimes the “old school” stuff works out just fine if you keep up with maintenance.
