I’ve actually had both on different houses—felt on my old place, synthetic on the current one. The felt definitely got brittle after a few years, especially where it was exposed at the edges or around vents. I remember patching a spot near the chimney and the stuff just crumbled in my hands. That roof was a pretty standard pitch, nothing super steep, but we get a lot of freeze/thaw cycles here and I think that sped up the wear.
With synthetic, I haven’t noticed any of that cracking or tearing, even after a couple of rough winters. It feels a lot tougher, almost like a tarp. Breathability is still a bit of a mystery to me, though. Some folks say synthetic doesn’t “breathe” as well, but I haven’t seen any moisture issues in the attic so far. Maybe it’s more of a problem on really low-slope roofs, like your neighbor’s? I do wonder if the slope makes a bigger difference than the material sometimes.
Anyway, if you’re worried about longevity, I’d lean synthetic, but I get the mixed reviews. Every roof seems to have its own personality...
- Totally get what you mean about every roof having its own “personality.”
- I went with synthetic on my place last year. Just seemed like the safer bet after hearing stories about felt falling apart, especially in wet climates (I’m in the PNW, so rain is a given).
- Haven’t noticed any moisture issues either, and my attic’s actually stayed drier than I expected.
- Slope probably does matter more than people think—my neighbor’s got a really low pitch and fights leaks no matter what underlayment he uses.
- It’s kind of reassuring to hear someone else say synthetic holds up better. Makes me feel like I didn’t overthink it for nothing...
Funny you mention the PNW—I've seen more than a few roofs up here where felt just didn’t stand a chance. There was this one house I inspected last winter, maybe 15 years old, and the felt underlayment had basically turned to mush in spots. The shingles looked fine from the street, but once you got up there, you could see where water had crept in along the low-slope sections. The attic was musty, insulation was clumping... not a great scene.
On the flip side, I’ve also come across some older synthetics that held up surprisingly well, even after a decade or so. One homeowner told me he’d picked synthetic mostly because his installer said it was “the new thing,” but he ended up being glad for it after a couple of those classic sideways rainstorms we get. His attic was bone dry, and the plywood underneath looked almost new.
I do wonder sometimes if folks underestimate how much roof pitch changes the game. Like you said, your neighbor’s low slope is just asking for trouble, no matter what’s underneath. I’ve seen some people try to compensate with extra layers or ice-and-water shield, but it’s never quite as bulletproof as a steeper roof.
Curious if anyone’s had issues with synthetic getting slippery during install? I’ve heard a few roofers grumble about that, especially on steeper pitches. Also, has anyone noticed any difference in noise during heavy rain? Some folks swear synthetic makes things louder, but I haven’t really noticed it myself.
It’s wild how much these little details—underlayment type, slope, climate—can add up over time. Makes me think there’s no one-size-fits-all answer, but it’s always interesting to hear what’s actually working (or not) for people in different spots.
I do wonder sometimes if folks underestimate how much roof pitch changes the game.
Yeah, I totally underestimated this when I bought my place. The inspector mentioned the low slope but I figured “how bad could it be?” Turns out, pretty bad. My felt underlayment was toast after just 8 years. Haven’t noticed any noise difference with synthetic, but I’m still paranoid every time it rains sideways.
Pitch really does make a bigger difference than most people realize. Low slope is just brutal on underlayment longevity, especially if you’re in an area that gets a lot of wind-driven rain. I’ve seen felt underlayment fail in less than a decade on low-slope roofs, even when everything else looked fine from the outside. It’s not always obvious until you get a heavy storm and suddenly there’s water where it shouldn’t be.
Switching to synthetic was probably the right call. The newer synthetics are definitely more resilient against moisture and don’t break down as fast as felt, especially when they’re exposed to standing water or repeated wet/dry cycles. I get the paranoia, though—once you’ve had one failure, it’s hard not to worry every time the weather turns ugly.
Noise-wise, I haven’t noticed much difference either, unless you’re dealing with metal roofing where underlayment can sometimes muffle or amplify sound depending on how it’s installed. With shingles, it’s usually a non-issue.
If it helps, you’re not alone in missing the warning signs early on. Inspectors will mention low slope but rarely spell out just how much faster things wear out. It’s one of those lessons you only learn by living through it (or fixing it). At least with synthetic, you should get a longer run before needing to worry again—assuming the install was solid and your flashing is tight.
One thing I’d keep an eye on: make sure your attic ventilation is up to snuff. Poor airflow can cook both felt and synthetic from underneath, especially on low slopes where heat and moisture get trapped more easily.
It’s frustrating, but you caught it before major damage set in. That’s more than a lot of folks manage.