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

I’ve seen synthetic get a little brittle in some of the colder jobs we’ve done up north, especially if it sits exposed for a few weeks in winter. It doesn’t always crack, but it definitely loses that flexibility you get when it’s new. Felt seems to stay more forgiving, even after years under shingles. One thing I’ve noticed - on steep slopes, synthetic can be a pain if there’s frost or dew, way slicker than felt. Ever had issues with crews slipping around on it?

- I’ve actually had the opposite experience with synthetic, at least down here in the Midwest. Ours held up fine through a couple surprise snowfalls before the shingles went on - didn’t get brittle, just a little stiff.
- Felt always seemed to tear easier for me, especially if it got wet or windy before we finished.
- The slickness is real though... nearly slid right off my garage roof one frosty morning. Ended up throwing down some old towels just to get traction.
- Maybe it’s just the brand or type? There’s so many now, it’s hard to keep track.

That slickness is no joke -

The slickness is real though... nearly slid right off my garage roof one frosty morning.

The wind thing with felt is a nightmare - seen it happen more than once on jobs where the shingles got delayed. One good gust and you’re chasing strips of black paper down the street. I get what you mean about synthetic being slippery, though. First time I tried walking on it in the morning dew, I nearly did the splits. Some brands are way worse than others for that, too.

What I’ve noticed is, if you’re in a spot with unpredictable weather or you can’t get the shingles on right away, synthetic usually holds up better. It doesn’t wrinkle up or tear as easily if it gets wet, and it’s a lifesaver if you get a surprise rainstorm mid-project. But like you said, not all synthetics are created equal - some feel sturdy, others are just glorified plastic bags.

I do wish there was a standard rating system so you could actually compare them side by side. Right now, it’s kind of a guessing game unless you’ve tried a bunch. For my own place, I went with a heavier synthetic and it’s been solid so far, but I still throw on roof jacks if there’s any frost... not risking another slip.

I’ve run into the same thing with felt - one windy afternoon and it’s like a parade of black streamers across the neighborhood. I’ve also had crews try to weigh it down with whatever was handy, but that only works until the next gust. Synthetic definitely seems to stay put better, especially if you’re stuck waiting a few days for shingles. The slipperiness is no joke, though. I remember one guy on my team nearly sliding right off a low-slope roof after a heavy dew. We started keeping a stash of those grippy shoe covers in the truck just for that reason.

One thing I’ve noticed managing different properties is that synthetic underlayment tends to hold up better if there’s any delay between underlayment and shingles - especially during rainy spells. Felt just doesn’t recover once it’s soaked or wrinkled, and then you’re dealing with bubbles under your shingles later on. But I’ve also seen some of the cheaper synthetics tear almost as easily as felt if they’re not fastened down well or if you get a lot of foot traffic.

For anyone weighing options, here’s what’s worked for me step-by-step:
1. Check the weather forecast before scheduling - if there’s any chance of rain or wind, lean toward synthetic.
2. Go for a heavier synthetic if you can swing it budget-wise; the lighter stuff just doesn’t inspire confidence.
3. Always use roof jacks or harnesses when there’s dew or frost, no matter what underlayment you pick.
4. If you have to use felt (budget or code reasons), double-check your fastening pattern and try to get shingles on ASAP.

I’m curious - has anyone tried those newer “walkable” synthetics? Some brands claim they’re way less slippery, but I haven’t had a chance to test them out yet. Wondering if they actually make a difference or if it’s just marketing...

- Used both, and honestly, synthetic’s been way easier for us - especially when the weather turns.
- Did try one of those “walkable” synthetics last fall. Felt grippier than the cheap stuff, but still not like walking on plywood.
- Noticed it scuffs up pretty quick if you’re dragging tools around.
- Haven’t had it tear yet, though, which is better than felt in my book.
- Still wouldn’t trust it much if there’s frost - those shoe covers are a must.

Yeah, I hear you on the scuffing - synthetic definitely takes a beating if you’re hauling ladders or tossing bundles around. Still, I’d rather deal with a few marks than patching tears in felt after a windy night. Those “walkable” synthetics are a step up, but nothing’s perfect when there’s frost. Been there, slid that... shoe covers are a lifesaver.

Been there, slid that... shoe covers are a lifesaver.

Man, I know exactly what you mean about sliding around. First time I tried walking on synthetic with a bit of frost, I nearly ended up in the neighbor’s yard. Those “walkable” ones are better, but nothing’s really slip-proof when it gets icy.

I’ve only worked with felt a couple times, but every time the wind picked up, it was like playing whack-a-mole with the tears. One job, we came back after a storm and half the felt was shredded - boss was not happy. With synthetic, yeah, it gets scuffed up, but at least it’s still there the next morning.

Still, I kinda miss how felt lays down flat right away. Some of the synthetics curl up at the edges if you don’t tack ‘em just right. Guess it’s always a trade-off. For me, I’d rather deal with a few scuffs than have to redo a whole section after a windy night.

I hear you on the wind and felt - had a job last fall where we spent more time chasing torn pieces than actually laying shingles. Synthetics aren’t perfect, but I’ve noticed they hold up better in heavy rain too. Still, nothing beats how easy felt is to roll out when you’re in a hurry... just wish it didn’t turn into confetti every time the weather turns.

Felt’s definitely got its place, but man, I’ve had days where it felt like I was in a Three Stooges skit - one gust and you’re chasing bits of black paper across the neighbor’s yard. I get what you mean about how quick it is to roll out, though. When you’re racing the weather, nothing’s faster. But after a couple jobs where we had to redo sections because the felt just shredded in a storm overnight, I started leaning more on synthetics. They’re not perfect - sometimes they wrinkle up weird or get slippery - but at least they don’t disintegrate if you get caught by surprise rain or wind.

Still, for smaller jobs or when the weather’s calm, I’ll grab felt just for speed. It’s cheap and easy. But if there’s any chance of a delay before shingles go on, synthetic saves me headaches. Guess it depends on how much risk you want to take with the forecast...

I hear you on the felt flying everywhere - had a job last spring where we spent more time chasing it than laying it down. But I’ve also had synthetic wrinkle up so bad in the sun that it looked like a potato chip bag. One thing I’ve noticed is, if you’re working on a steep pitch, synthetic’s grippier underfoot (unless it’s wet, then it’s like ice). For long delays or unpredictable weather, I’d rather deal with the quirks of synthetic than risk redoing half the work. But yeah, if you can shingle same day, felt’s hard to beat for speed and price.

I get the appeal of felt for quick jobs, especially if you’re sure you’ll have shingles down before the weather turns. But honestly, I think both options have their headaches - felt blows around and tears, synthetic wrinkles and can get slick. What gets me is how little either option really addresses long-term durability or environmental impact.

Here’s where I’ll push back a bit: if we’re talking about what holds up *over time*, neither traditional felt nor most synthetics are really built to last more than a few months exposed. I’ve seen plenty of roofs where the underlayment was shot long before the shingles were ready to be replaced. And when you factor in disposal, felt’s basically landfill fodder, and most synthetics aren’t much better - just more plastic piling up.

I started using recycled-fiber underlayments a couple years ago (think recycled polyester blends), and while they cost more upfront, they’ve held up better in weird weather swings - less curling, less tearing, and they don’t turn into a slip-and-slide the second there’s dew. Plus, some of them are actually designed to break down faster or be recycled again, which feels like a step in the right direction.

Not saying they’re perfect - nothing is - but if you’re looking at the big picture (durability *and* footprint), it’s worth considering alternatives outside the usual felt vs. synthetic debate. Upfront cost stings a bit, but I’d rather pay for something that won’t just end up in a landfill after one hailstorm or heatwave.

Curious if anyone else has tried these newer options? I’m in the Midwest, so we get everything from ice to 100-degree days... so far, no regrets on making the switch.

That’s interesting about the recycled-fiber stuff - haven’t tried it myself, but I’m curious how it handled heavy wind-driven rain. Did you notice any seepage or edge curling after a bad storm? Around here (southern plains), I’ve seen synthetics hold up okay, but they get slick as ice when wet and can be a pain during install. Wondering if the recycled blends are any better for traction or if it’s more or less the same story.

I get where you’re coming from - those synthetic sheets can turn into a skating rink when they’re wet, and that’s no joke if you’re up there trying to keep your footing. I’ve tested a few recycled-fiber underlayments after a couple of nasty spring storms (I’m in north Texas), and here’s what I noticed: edge curling was less of an issue than with old-school felt, but I did see some minor seepage at the seams where we didn’t overlap enough. Nothing catastrophic, but it’s something to watch.

Traction-wise, the recycled stuff felt a bit grippier than the slick synthetics, especially when there was dew or light rain. Not perfect, but I wasn’t sliding around as much. Still, if you get a real gully-washer with wind, any underlayment can get compromised if it’s not fastened down tight or if you’ve got exposed edges.

Honestly, every material has its trade-offs. I’d say the recycled blends are worth a shot for traction alone, but don’t expect miracles in a full-on storm unless your install is buttoned up tight. Good luck if you give it a try - curious to hear how it goes in your neck of the woods.

I’m with you on the recycled blends being a step up for traction - those synthetic sheets are like ice skates when it’s damp, and I’ve had my share of “whoops” moments. But I still wonder about long-term durability. The eco-friendly stuff sounds great, but does it really hold up after a few years of Texas sun and hail? I’ve seen some of those recycled underlayments get brittle faster than expected. Maybe it’s just the brands I tried, but I’m not totally sold yet. Still, anything that keeps me from sliding off the roof is worth considering...

But I still wonder about long-term durability. The eco-friendly stuff sounds great, but does it really hold up after a few years of Texas sun and hail? I’ve seen some of those recycled underlayments get brittle faster than expected.

I hear you on that. I tried one of those “green” underlayments a few years back - looked good on paper, but after two summers in central Texas, it started curling at the edges. Not a total disaster, but definitely not what I’d hoped for. The sun here just eats up anything that’s not built tough.

I will say, though, the newer synthetics (not the recycled blends) seem to be holding up better for me. I put down a synthetic underlayment on my shed roof about five years ago, and it’s still flexible, no cracking or brittleness yet. But yeah, the traction is a whole other story - felt is way grippier when it’s damp. I’ve had a few “skating rink” moments myself.

Honestly, I’m still on the fence too. If you’re worried about longevity, maybe stick with a heavier felt or one of the premium synthetics (not the bargain stuff). The cheap recycled ones just don’t seem to last in this heat. But I totally get wanting something that doesn’t send you sliding off the roof... safety first, right?

The sun here just eats up anything that’s not built tough.

That’s been my experience too - Texas sun is brutal, and I’ve seen plenty of “eco” underlayments get crispy way sooner than advertised. But here’s what I keep wondering: has anyone actually had a premium felt last more than 10 years without issues? I’ve inspected a few older roofs where the felt was basically dust. Maybe it’s just the climate, but I’m not convinced any underlayment is truly “long-term” here. Anyone seen otherwise?

I’ve inspected a few older roofs where the felt was basically dust.

Same here - my neighbor’s roof had “premium” felt and it just crumbled when we pulled up the shingles after about 12 years. Has anyone tried those heavier synthetics? Wondering if they actually hold up better in this heat, or if it’s just marketing.

Wondering if they actually hold up better in this heat, or if it’s just marketing.

I’ve pulled up both types here in Texas, and the synthetics definitely seem less brittle after a decade or so. The heavier ones (like 40 mil) don’t tear as easy when you’re walking on them, either. But I’ve heard some folks say they can get slippery, especially if there’s any dew. I’d still pick synthetic for heat, but maybe not the super cheap stuff.

I’ve had both on my place - old felt under some 3-tab shingles, and then synthetic when we redid the roof a few years back. The felt was basically dust after 15 years in the Texas sun. Synthetic’s holding up better so far, but I do notice it’s a pain to walk on if there’s any moisture, like you said. I’m curious if anyone’s had issues with synthetic getting brittle after, say, 20+ years? Or does it just outlast the shingles and you never really see it fail?

Also, has anyone tried using synthetic under metal roofing? I’ve only done asphalt, but I wonder if the heat build-up under metal makes a difference.