Which holds up better over time: felt or synthetic underlayment?

I get why synthetics are popular, but I’ve slipped more than once on those in the morning... not fun. For me, the cost difference is hard to ignore too - felt’s just easier on the wallet if you’re careful about exposure time.

That’s been my experience too. I’ve done a couple of roof repairs over the years (asphalt shingles, nothing fancy), and every time I look at the price tags, felt just makes more sense for my budget. The synthetic stuff is lighter and all, but it’s not cheap. And yeah, it gets slick - especially with a bit of dew or frost. Nearly took a tumble myself last fall.

I do wonder about long-term durability though. I keep hearing that synthetics can last months exposed, while felt starts curling up or tearing if you get a surprise storm before the shingles go on. But then again, if you’re planning your project right and not leaving things open for weeks, does that really matter? I’ve never had felt fail under shingles as long as I got everything covered up within a few days.

One thing I’ve noticed: the heavier 30# felt seems to hold up better than the lighter stuff, especially around weird angles and valleys like you mentioned. My house is a basic ranch, but there’s one spot where two rooflines meet and water always wants to sneak in. The thick felt just seems to hug those spots better.

I’m in the Midwest, so we get a lot of freeze/thaw cycles and some pretty wild storms. I haven’t seen much difference in performance once the shingles are down - felt or synthetic, both seem fine as long as nothing gets torn up during install. But if you’re paying out of pocket and watching every dollar, it’s hard to justify spending double or more for synthetic unless you really need that extra exposure time.

Curious if anyone’s actually had synthetic outlast felt by years under normal shingles? Or is it mostly about convenience during install? For me, as long as I’m careful with timing and don’t cheap out on the weight, felt still wins on price.

I do wonder about long-term durability though. I keep hearing that synthetics can last months exposed, while felt starts curling up or tearing if you get a surprise storm before the shingles go on. But then again, if you’re planning your project right and not leaving things open for weeks, does that really matter?

That’s been my thought too. I helped my uncle redo his garage roof last summer - he insisted on the heavy 30# felt, mostly because he’s old school and likes what he knows. We got hit with a nasty thunderstorm two days after laying it down, but as soon as we got back up there, the felt was still in good shape. No tears or leaks under the tarp we threw over the ridge.

I’ve heard some folks say synthetic is a lifesaver if you’re doing a big job solo or have unpredictable weather windows, but for smaller projects where you can finish in a weekend, felt seems to hold its own. I’m curious though - has anyone had issues with mold or moisture under synthetic long-term? I’ve never seen it myself, but I wonder if it breathes differently than felt. Maybe it depends on attic ventilation?

- Had a similar situation last fall - used felt on my shed, got rained on before shingles went up, but it bounced back fine after drying out.
- For bigger jobs, I probably would’ve gone synthetic just for peace of mind if things dragged out.
- Haven’t noticed any mold with synthetic, but I always make sure the attic’s got good airflow.
- Honestly, if you’re quick with the install and watch the weather, felt still seems solid to me.
- Only real downside I’ve seen is felt gets slippery when wet - almost wiped out once...

Title: Anyone Notice a Difference in Longevity Between the Two?

That’s interesting about the felt bouncing back after rain - did you notice any wrinkling once it dried out, or did it lay flat again? I’ve always wondered if that impacts shingle life long-term. The slip factor with wet felt is real though... had a sketchy moment myself last year on a steep pitch, and honestly, it made me rethink using it for bigger projects.

I do like that synthetic seems to handle moisture better if the weather turns, but I’m not sure about its environmental impact - anyone looked into whether it’s recyclable or just ends up as landfill? Sometimes I worry we’re trading off durability for more plastic waste. But yeah, as long as there’s good attic airflow, mold doesn’t seem to be an issue either way.

For smaller jobs where you can get shingles down fast, felt still seems like a solid choice to me too. Curious if anyone’s actually seen synthetic last longer under real-world conditions, or if it’s mostly just about peace of mind during install.

Curious if anyone’s actually seen synthetic last longer under real-world conditions, or if it’s mostly just about peace of mind during install.

On a couple of storm jobs after hail, I’ve pulled up shingles where the synthetic underlayment looked almost new, even after 7-8 years. Felt, on the other hand, tends to get brittle and tear up when you’re removing old shingles - especially if there’s been any leak history. But I do wonder about the landfill issue with all that plastic. Anyone seen a recycling option for synthetic? I haven’t run across one locally.

I’ve seen the same thing - synthetic underlayment just shrugs off years of abuse, even when the shingles are trashed. Felt’s basically paper mache after a few wet seasons, especially if there’s been any leaks or ice damming. The landfill issue bugs me too, though. Around here, nobody’s recycling synthetic yet... it all goes straight to the dump. Not ideal, but I’d rather deal with that than a rotten deck from failed felt.

That lines up with what I’ve seen on a few properties - synthetic just doesn’t break down the way felt does, even after years of rough weather. The landfill thing is a headache, though. I keep hoping someone will figure out a recycling option for synthetics soon... but yeah, replacing rotten decking is a much bigger hassle and cost.

Yeah, the landfill issue with synthetics bugs me too. I get why folks like them - they really do hold up better in nasty weather, and I’ve seen felt just turn to mush after a few years of heavy rain. But then you’re stuck with all that plastic that’s not going anywhere for decades. It’s a trade-off, I guess. I’d rather not be tearing up rotten decking every ten years, but I also hate the idea of piling up more stuff that won’t break down.

I keep hearing rumors about recycling programs in the works, but nothing concrete yet. Until then, it’s just picking the lesser evil. At least with synthetics, you’re not dealing with leaks as often, which is a relief. Still, I wish there was a truly green option that didn’t cost an arm and a leg or fall apart after one bad storm. Maybe someday...

I keep wondering if anyone’s actually seen a synthetic underlayment get reused or recycled, or is it just all talk right now? I’ve only ever seen it go straight to the dump after a tear-off. Maybe there’s something happening in bigger cities, but around here, it’s just landfill.

I’ve only ever seen it go straight to the dump after a tear-off.

Same here - after my recent roof project, the crew just bundled up the old synthetic stuff and tossed it. I asked if it could be recycled, and got a look like I’d suggested composting asphalt. Maybe there’s some cutting-edge recycling in the big cities, but in my small town, it’s definitely landfill-bound. On the bright side, at least the synthetic underlayment held up better than the felt did on my neighbor’s place... his was basically mulch by year ten.

on the bright side, at least the synthetic underlayment held up better than the felt did on my neighbor’s place... his was basically mulch by year ten.

That lines up with what I’ve been seeing, too. Synthetic definitely seems to outlast felt, especially if you’re in an area with wild temperature swings or heavy rain. I helped on a job last summer where we pulled up 12-year-old felt and it just crumbled - total mess, stuck to the decking in spots. The synthetic stuff from a similar-age roof down the street came off in big sheets and was still tough, even after all those years.

It’s a bummer about the landfill thing, though. I had the same thought about recycling and got a blank stare from the crew chief. Maybe that’ll change eventually, but for now, it feels like you just have to pick what’ll last longer and keep things dry as long as possible.

Anyway, sounds like you made a solid call going with synthetic. At least you won’t be dealing with “mulch” if you ever need another tear-off down the road...

At least you won’t be dealing with “mulch” if you ever need another tear-off down the road...

Yeah, “mulch” is about right - felt just doesn’t hold up over time. I’d still love to see a synthetic option that’s easier on the environment, but for now, longevity matters a lot. You probably saved yourself a headache later.

I’d still love to see a synthetic option that’s easier on the environment, but for now, longevity matters a lot.

That’s the sticking point for me too. Synthetics definitely outlast felt - no contest there, especially if you’re in a climate with big temperature swings or lots of rain. But most of the synthetics are plastic-based, and I haven’t seen much info on how recyclable they actually are once you tear them off. Felt turns to “mulch,” sure, but at least it’s mostly organic material.

I’ve heard about some newer underlayments made from recycled materials or even bioplastics, but they’re not widely available yet. Has anyone actually used one of those? I’m curious if they hold up as well as the standard synthetics. For now, I get why people go with the longer-lasting stuff - nobody wants to redo their roof every decade - but I wish there were more eco-friendly options that didn’t sacrifice durability.

If you’re in a spot with lots of sun or heavy storms, synthetic is probably the safer bet for now. Just wish we didn’t have to pick between longevity and landfill...

That’s exactly where I’m at - torn between wanting something that’ll last and not loving the idea of more plastic waste. I’ve seen a couple brands touting recycled content, but nothing local yet. Honestly, it feels like we’re stuck waiting for the industry to catch up. At least felt will break down eventually, but it just doesn’t hold up in our wet winters. Wish there was a clear win for both durability and the planet...

I hear you on the plastic waste thing. I ended up going with felt last time because it just seemed like the “safer” choice for the environment, but honestly, it didn’t hold up well at all once the rainy season hit. My neighbor tried a synthetic underlayment that was supposed to be partially recycled, but the price was way up there. I wish there was a budget-friendly option that didn’t feel like a compromise... I’m still patching leaks every spring.

Title: Which holds up better over time: felt or synthetic underlayment?

Felt’s definitely got that eco-friendly vibe, but in wet climates it just doesn’t last. I’ve seen a lot of roofs where the felt starts to wrinkle or even tear after a couple seasons of heavy rain, especially if there’s any pooling. Synthetics tend to resist water better and don’t break down as fast, but yeah, the cost can be a shock. One thing I’ve noticed - if you’re set on felt, using a heavier weight (like 30 lb instead of 15 lb) helps a bit, though it still won’t match synthetics for longevity. It’s always a trade-off... I wish there was a perfect middle ground too.

That’s interesting about the heavier felt - makes sense it’d hold up a bit better, but I’ve heard similar stories about it still not lasting as long as synthetics. I’m in the Pacific Northwest, so rain is just a part of life here, and honestly, I’m getting nervous about picking the wrong thing. Has anyone actually had synthetic underlayment on their roof for more than 10 years? Curious if it really holds up that much better in practice, or if it just looks good on paper.

Also, does the type of shingles you use make any difference? I’ve got basic asphalt shingles, nothing fancy. Wondering if that changes how well either underlayment lasts... or if it’s really all about the climate and installation.

I’ve managed a few properties out here in the rainy PNW and have seen both types in action. Honestly, synthetic has held up better on the roofs I’ve had eyes on - especially when you get those stretches of non-stop drizzle. The felt just seems to get soggy and break down faster, even the heavier stuff. As for shingles, with standard asphalt, I haven’t noticed much difference in how the underlayment lasts... seems like the install and how well it’s sealed up are way bigger factors. The climate definitely does a number on both, but synthetic seems to win out if you’re dealing with as much rain as we get.

- Been crawling around on roofs in the PNW for years - synthetic’s definitely saved my bacon more than once when the rain just wouldn’t quit.
- Had a job last winter where we used felt because the homeowner was old school... two weeks later, half of it looked like wet cardboard.
- Not saying felt’s useless, but man, once it gets soggy, it’s toast. Synthetic hangs tough, even when you forget to tarp overnight (don’t ask).
- I’ll agree though - if your installer’s sloppy, doesn’t matter what you use. Water finds every mistake.

Not saying felt’s useless, but man, once it gets soggy, it’s toast. Synthetic hangs tough, even when you forget to tarp overnight (don’t ask).

That lines up with what I see during inspections - felt just doesn’t bounce back after a good soaking. But I’m curious, did you notice any difference in how the shingles laid over each type? Sometimes I see wrinkles with felt if it’s gotten wet. And yeah, installer skill really is half the battle... even the best underlayment can’t fix a bad flashing job.