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

Felt might look sad sagging there, but at least it doesn’t end up in my neighbor’s yard.

That’s a fair point - watching synthetic blow around is pretty discouraging. I keep wondering about the environmental impact too. Has anyone found a synthetic that actually breaks down over time, or are they all just destined for landfill?

Haven’t seen a synthetic yet that actually breaks down in any reasonable time frame. Most of the stuff out there is polypropylene or polyethylene, and those just hang around forever - maybe not blowing into the neighbor’s yard, but definitely not composting either. I’ve heard a couple of brands claim “eco-friendly” or “recyclable,” but in practice, I don’t know anyone who’s actually recycled underlayment after a tear-off. It usually just ends up in the dumpster.

Felt’s not perfect either, but at least it’s mostly paper and asphalt, so it’ll eventually break down if it gets buried. The trade-off is it doesn’t last as long under the shingles, especially in hot climates or if it gets wet before the roof goes on. I’ve had jobs where the felt just turned to mush after a rainstorm, which is a pain.

Honestly, I wish there was a truly biodegradable synthetic, but I haven’t seen one that holds up during install and then breaks down after. If anyone’s found something like that, I’d be interested too.

- Totally get where you’re coming from on the “eco” claims. I’ve seen the same - marketing loves to slap green labels on stuff that’s not really green once you dig into it.
- Polypropylene and polyethylene just don’t go anywhere. I pulled up some synthetic underlayment after 5 years (hail damage, needed a re-roof) and it looked almost new, even after baking under Texas sun. Great for durability, not so great if you care about what ends up in the landfill.
- Felt’s more “natural,” but like you said, it can fall apart fast if you get unlucky with rain or delays. I’ve had to redo sections after a storm turned it into a soggy mess. Not fun.
- I keep hoping someone’s going to come out with a truly compostable synthetic, but right now it’s all trade-offs. Either you get something that lasts, or something that breaks down, but not both.
- I’ve heard rumors about bio-based plastics being tested in Europe, but nothing practical here yet. Would love to see one that actually works for installs and isn’t just greenwashed.
- One thing I’ve tried: using the thickest felt I can find (30# instead of 15#). It holds up a bit better if there’s a delay, but still not perfect.
- At the end of the day, it feels like picking the lesser evil. Either you get a product that lasts but sticks around forever, or one that breaks down but might cause headaches during install.
- If anyone does stumble on a legit biodegradable synthetic that survives install, I’m all ears too. For now, I just try to minimize waste where I can and hope better options show up soon.

At the end of the day, it feels like picking the lesser evil. Either you get a product that lasts but sticks around forever, or one that breaks down but might cause headaches during install.

That about sums it up. I’ve inspected roofs where the synthetic underlayment looked untouched after a decade, but then you think about all that plastic just sitting there when it’s finally torn off. Felt definitely has its headaches - especially if you get a surprise rainstorm mid-project. I’ve seen more than one job where soggy felt led to leaks before the shingles even went on. Still waiting for someone to crack the code on a tough, truly compostable option... until then, it’s just managing trade-offs and hoping for good weather.

Yeah, I hear you on the trade-offs. I went with felt last summer because it was what my dad always used, but man, that stuff is unforgiving if you get caught by a pop-up thunderstorm. Ended up with a tarp flapping around at 2am and a very grumpy spouse. My neighbor swears by synthetic - says it’s like “roofing with yoga mats” - but then you’re stuck with all that plastic waste down the line. Wish there was an option that didn’t make me feel guilty either way...

I totally get the guilt about all the plastic waste - synthetic does feel a bit like cheating the environment. But after dealing with a couple of insurance claims from leaks (thanks, Midwest storms), I’ve started leaning toward synthetic for rental properties. It just holds up better if the roofers get delayed or we get surprise rain. That said, it’s not perfect - slippery as heck to walk on, and yeah, it’s more landfill fodder. I wish someone would invent a biodegradable version that actually works...

Slippery is right - I nearly did the splits last summer trying to cross a roof with synthetic down. Not my proudest moment, but at least nobody got it on video, right? I hear you on the guilt, though. It’s weird knowing this stuff will outlive me (and probably my grandkids), but man, after seeing what Midwest rain does to old felt, I get why people go synthetic for rentals.

One thing I noticed - felt tears super easy if you’re dragging bundles or tools across it, especially when it’s hot and sticky. Synthetic seems to bounce back unless you really gouge it. But then again, every time I’m up there and it rains, I feel like I’m ice skating... not exactly OSHA-approved.

Has anyone actually tried those “eco” underlayments? I saw one at a supply house that claimed to be biodegradable, but the rep just kind of shrugged when I asked if it actually held up in storms. Curious if anyone’s risked it or if it’s just marketing fluff.

Has anyone actually tried those “eco” underlayments? I saw one at a supply house that claimed to be biodegradable, but the rep just kind of shrugged when I asked if it actually held up in storms.

I’ve tested a couple of those “eco” options on smaller sheds, but honestly, durability’s still a big question mark. They break down faster than synthetics, especially if exposed before shingles go on. Not sure I’d risk them on a full house yet, especially in storm-prone areas. Synthetic’s still the safer bet for now, even if it’s a little guilt-inducing.

They break down faster than synthetics, especially if exposed before shingles go on.

That’s been my experience too. Tried one of those “eco” felts on a detached garage last year, just as a test run. Looked good out of the wrapper, but after a week of rain and wind (didn’t get shingles on as fast as planned), it started curling at the edges and got soft in spots. Not what you want to see.

I get the appeal of going green, but if you’re in an area where storms can roll in with little warning, synthetics are still way more forgiving. They don’t wrinkle up or turn to mush if they get wet for a few days. Felt’s okay for quick jobs or mild climates, but I’d be nervous using anything “biodegradable” unless you’re 100% sure you’ll get it covered right away.

Honestly, until they come up with something that holds up like synthetic but breaks down when you actually want it to, I’m sticking with what works - even if it means feeling a bit guilty about the landfill.

Yeah, I’ve had a similar run-in with the “green” felt stuff. Tried it on my shed, thinking I was doing the planet a favor, but after a few days of drizzle and one good gust, it looked like a soggy tortilla. Had to scramble to get the shingles on before it turned into compost right there on my roof.

I get wanting to be eco-friendly, but honestly, synthetic’s just less stressful if you can’t predict the weather (which, let’s be real, is most of us). I’ve left synthetic underlayment exposed for almost two weeks once - thanks to a surprise family emergency - and it was still flat and solid when I finally got back to it. Felt would’ve been toast.

Only thing I’ll say is synthetic can be a little slippery if you’re up there in the morning dew. Nearly did the splits once - my neighbor still laughs about it. But for holding up under unpredictable skies? I’ll take that trade-off over soggy felt any day.

I’ve been researching this a lot since buying my place last year. The synthetic stuff seems to win out for durability, especially if there’s any delay before shingles go on. I do worry about the slipperiness, though - my roof’s got a pretty steep pitch, so that’s not nothing. Felt just doesn’t seem to handle wet weather at all, at least from what I’ve seen and read.

I do worry about the slipperiness, though - my roof’s got a pretty steep pitch, so that’s not nothing.

That’s a legit concern. I’ve seen a few folks take a tumble on synthetic underlayment, especially when there’s morning dew or after a light rain. Some brands claim to have “grip strips,” but honestly, it still feels slick compared to felt. Have you looked into any of the newer synthetics with textured surfaces? I’m curious if anyone’s actually noticed a difference in real-world use, or if it’s just marketing. Also, what kind of weather do you get most - lots of wind, heavy rain, or more sun exposure? That can really change how each type holds up over time.

Some brands claim to have “grip strips,” but honestly, it still feels slick compared to felt.

I hear you on that. The “grip strip” thing is mostly marketing fluff in my experience - maybe a little better than the old synthetics, but nothing like felt when it comes to traction. I’ve been on a few roofs where the synthetic was supposedly “high-traction” and still found myself sliding around, especially early in the morning or after a quick shower. Felt just has that gritty texture that gives you a bit more confidence underfoot, even if it tears easier.

That said, I wouldn’t write off all synthetics. Some of the newer textured ones (like GAF Tiger Paw or Owens Corning Deck Defense) are a step up from the shiny plastic stuff from a few years back. Still not perfect, but if you’re careful and wear good shoes, it’s manageable. On a steep pitch though, I’d be extra cautious no matter what you use.

As for weather - if you’re in a spot with lots of wind or heavy rain, synthetics do have an edge in terms of water resistance and they don’t wrinkle up like felt can. I’ve seen felt bubble and buckle after a big storm, which can mess with shingle install. Synthetics also hold up better if your roof sits exposed for a while before shingles go on. But if you’re somewhere hot and dry, felt can last just fine and is usually cheaper.

One thing I’ll say: if you’re DIYing this, don’t let the “slip-resistant” label lull you into thinking it’s safe to walk on any synthetic without fall protection. I’ve seen too many close calls from folks trusting the marketing.

If it were my own roof and I had to pick between the two for a steep pitch, I’d probably lean toward felt just for the grip factor during install - unless I knew for sure the shingles would go on right away and weather wasn’t an issue. But for long-term durability, synthetics do win out once everything’s buttoned up.

Curious if anyone’s actually found a synthetic that feels as grippy as felt? I haven’t yet, but maybe there’s something new out there I missed...

That’s a solid breakdown. I’ve noticed the same thing - felt just feels safer underfoot, especially when things get a little damp. The newer synthetics are better than they used to be, but I still double-check my footing every step. You’re right about weather exposure though; I’ve seen felt wrinkle up in just a day or two of rain, and that can be a pain to fix. It’s kind of a trade-off, but your point about not trusting the “grip” marketing is spot on.

I hear you on the “grip” claims - some of those synthetic brands act like you’ll be able to moonwalk up a 10/12 pitch, but in reality, I’m still tiptoeing like I’m sneaking past a sleeping dog. Felt does feel more predictable underfoot, especially when it’s humid or there’s a bit of dew. But man, the way it bubbles and wrinkles after a good rain drives me nuts. Ever tried flattening out felt that’s been soaked and dried in the sun? It’s like wrestling a wet blanket.

On the flip side, I’ve seen some synthetics hold up through weeks of off-and-on rain without budging, which is impressive. But then again, I’ve also seen them get slick as snot if there’s any dust or pollen on them. Anyone else notice that? Maybe it’s just my luck.

I guess it comes down to what you’re willing to deal with - wrinkles and repairs with felt, or the occasional slip-and-slide with synthetics. Either way, I’m not trusting my life to any marketing slogan about “superior traction.”

You nailed it with the “superior traction” claims - marketing always oversells that part. I’ve had crews complain about both, honestly. Felt is more forgiving when you’re walking on it, but those wrinkles after a storm are a pain to fix, and if you leave them, they telegraph through the shingles. Synthetics are definitely tougher in wet weather, but yeah, pollen or even sawdust turns them into a skating rink. I guess it’s just picking your battles. I’ve started warning folks not to trust any underlayment too much when it’s damp or dirty... nothing replaces being careful up there.

I’ve started warning folks not to trust any underlayment too much when it’s damp or dirty... nothing replaces being careful up there.

That’s honestly the best advice. I used to think synthetic would be a game-changer, but after seeing my neighbor’s crew nearly wipe out on a pollen-covered roof, I get it now. Felt seemed “old school” to me, but those wrinkles you mentioned are real - my inspector pointed them out after a storm last spring. It’s wild how much the marketing glosses over the actual day-to-day headaches. You’re right, there’s no magic fix, just gotta stay cautious and pick what works for your situation.

It’s wild how much the marketing glosses over the actual day-to-day headaches.

I hear you, but I’d push back a bit on the “no magic fix” idea. Synthetic’s not perfect, but in my experience after a couple hurricanes, it held up way better than felt - especially when the shingles got peeled off. Felt just turned to mush. That said, synthetic gets slick as ice with any dust or pollen, like you mentioned. For me, it’s about weighing which headache you want: felt wrinkles and tears, or synthetic slipperiness and cost. Neither is flawless, but I’d still lean synthetic for storm zones.

I’ve seen a lot of roofs where the synthetic looked almost untouched after a few years, but I’ve also come across some that were curling at the edges - maybe installer error? Anyone else notice synthetic sometimes traps moisture if there’s a leak above? Just curious if that’s a common thing or just bad luck on my end.

Anyone else notice synthetic sometimes traps moisture if there’s a leak above?

Yeah, I’ve seen that too. Synthetic’s great for durability, but if water gets underneath, it doesn’t always dry out like felt does. Curling at the edges usually screams install issue - seen it when guys over-nail or don’t lap it right. Honestly, I trust synthetic more in the long run, but only if it’s put down right. Otherwise, you’re just asking for weird problems down the road...