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

Install makes a difference too. If it’s stretched too tight or not fastened right, wind or hail will find a way in.

Couldn’t agree more - install is half the battle. I’ve tried to save a buck with cheap felt before, but one hailstorm and it looked like Swiss cheese. The pricier synthetics sting up front, but they really do seem to take a beating and just keep trucking. Still, my wallet always tries to argue with my common sense...

That’s what gets me - does paying more for synthetic really pay off, or is it just marketing hype? I’ve seen some of those “eco-friendly” synthetics that claim to last 30+ years, but do they actually hold up in real-world weather? And has anyone noticed if they trap more heat underneath than felt does? My neighbor swears by the old-school felt, but his roof always seems to need patching after a big storm. Maybe it’s just bad luck... or maybe install really is everything.

I’ve seen both sides of this debate play out on job sites, and honestly, it’s not as cut and dry as some folks make it out to be. I’ve worked on roofs where the old felt was still hanging in there after 20 years, but I’ve also torn off plenty that turned to mush after just a decade - usually after a few rough winters or a stretch of heavy storms. The thing is, felt can be pretty forgiving if you’re dealing with mild weather, but once you get those sideways rains or a week of snow melt, it doesn’t always hold up.

Now, about synthetics - yeah, they cost more up front, but I’ve noticed they’re a lot tougher when it comes to resisting tears during install. That’s a big deal if you’re working on a windy day or if the roof sits exposed for a while before shingles go on. I remember one job last summer where we had to pause for almost two weeks because of supply delays. The synthetic underlayment didn’t budge, even after a couple storms rolled through. If that had been felt, I’d have been back up there patching holes.

As for the heat question, I’ve heard people say synthetics trap more heat, but in my experience, it’s not a huge difference - at least not enough to notice from inside the house. Maybe if you’re in Arizona or somewhere roasting hot, it could matter more. Around here (Midwest), it’s not something homeowners complain about.

One thing I will say: installation really does make or break it. I’ve seen felt jobs fail just because someone rushed and left gaps or didn’t overlap right. Same goes for synthetic - if you don’t fasten it down well, wind will find a way underneath.

Long story short, I lean toward synthetic for most jobs these days, especially if the budget allows. But I wouldn’t say felt is useless - it just needs a little more TLC and maybe isn’t the best pick if your area gets hammered by storms.

I get what you’re saying about synthetic being tougher, but I’m still not totally sold. My neighbor went with synthetic and had issues with it getting slippery when wet - made it a pain for the crew. Plus, the upfront cost is no joke if you’re on a tight budget. Maybe felt isn’t perfect, but for folks who don’t get crazy weather, I don’t see it as a total dealbreaker.

Yeah, I’ve seen that too - synthetic can get slick, especially if there’s morning dew or a light rain. It’s definitely something to watch for on steeper roofs. The cost is higher up front, no doubt, but it does hold up better if the shingles get delayed or if you’re in a spot with unpredictable storms. For milder climates and quick installs, felt still gets the job done. Just gotta weigh how long you expect it to be exposed and what kind of weather you’re dealing with.

I get the appeal of synthetic, but man, my wallet still cries a little every time I see those prices. I went with felt last year when I had to patch up the shed roof - figured if it was good enough for my grandpa’s house, it’d survive a few more seasons for me. Sure, it’s not as tough if you’re leaving it exposed for weeks, but if you’re quick with the shingles and not expecting a monsoon, felt’s way easier on the budget. Plus, I don’t miss sliding around like I’m in a slapstick comedy...

I hear you on the price difference - synthetic can be a tough sell when you’re just patching up a smaller roof or something you don’t expect to last forever. I’ve seen both used on properties I manage, and honestly, the main thing I notice is how much longer synthetic seems to hold up if there’s any delay before shingles go on. But then again, if you’re just doing a quick job and get the shingles down right away, felt seems to do fine for a few years.

One thing I’m always curious about is how these underlayments actually perform in different climates. Has anyone noticed felt breaking down faster in really humid areas? Or does synthetic ever get brittle in cold winters? I’ve had a couple tenants complain about leaks after heavy storms, but it’s hard to tell if that’s the underlayment or just old shingles giving up.

Anyone run into issues with warranties when using one type over the other? Sometimes manufacturers seem picky about what goes under their shingles...

One thing I’m always curious about is how these underlayments actually perform in different climates. Has anyone noticed felt breaking down faster in really humid areas? Or does synthetic ever get brittle in cold winters?

That’s a great point about climate. I’ve seen felt deteriorate pretty quickly in humid, coastal regions - almost like it absorbs moisture and starts to wrinkle or tear. Synthetics seem to resist that, but I have noticed some brands can get stiff and a bit slick when it’s freezing out, which isn’t ideal for installation. As for warranties, I’ve run into shingle manufacturers who’ll only honor coverage if you use their approved synthetic underlayment, especially on steeper slopes. It’s worth double-checking the fine print before you buy.

- Had both on my old house (asphalt shingles, Midwest).
- Felt was a pain after a few years - edges curled, and it tore up when I had to patch a vent.
- Synthetic held up better, but yeah, it got almost brittle when I tried to install it in January.
- Never had either one last as long as the shingles themselves, honestly.
- Curious if anyone’s seen a difference with metal roofs? Wonder if the underlayment matters as much there.

Curious if anyone’s seen a difference with metal roofs? Wonder if the underlayment matters as much there.

I’ve worked a few storm jobs where metal roofs got peeled back, and honestly, the underlayment was still a big deal. If water gets under the panels, you really want something that won’t just disintegrate after a couple seasons. Has anyone tried those peel-and-stick membranes under metal? I’m not sure if they’re overkill or actually worth it for hail-prone areas.

I went with a peel-and-stick ice/water shield under my standing seam metal roof - wasn’t cheap, but after a couple gnarly hail storms, I’m glad I did. Regular felt tore up fast on my old place. Synthetic seemed okay but got slippery during install.

Peel-and-stick ice/water shield is a solid move, especially under metal. I did the same thing after watching my neighbor’s roof take a beating in a hailstorm - his regular felt was shredded, and he had leaks all over. The upfront cost stings, but it’s hard to put a price on peace of mind when the weather turns nasty.

I get what you mean about synthetic being slippery. I tried it once during an August install, and nearly took a dive more than once. It holds up better than felt in most cases, but if you’re in an area that sees big storms or ice dams, nothing really matches the durability of a peel-and-stick barrier. Felt just doesn’t cut it long-term anymore, at least not where I am (Midwest).

It’s one of those things where you pay now or pay later. Sounds like you made the right call for your situation - especially with standing seam metal, which can be unforgiving if water ever gets underneath.

I’ve seen way too many cheap felt jobs come back to bite folks, especially after a rough winter or a stormy spring. Had a section of one of my buildings where the old felt just crumbled after a few years - water snuck in, and it was a mess. Synthetic’s not perfect, but it’s definitely held up better for me, and the peel-and-stick under metal is just peace of mind. You’re right about the cost, but I’d rather deal with that once than chase leaks every year.

- Makes sense, honestly. I’ve seen felt just disintegrate after a couple seasons, especially if it gets a lot of sun or moisture.
- Synthetic’s been more forgiving in my experience - less curling, less tearing when you’re working on it.
- Peel-and-stick is pricey, but yeah...not having to worry about leaks every spring feels worth it.
- Only thing I’d watch for is making sure it’s installed right - seen a few jobs where folks rushed and it still caused headaches.
- Sounds like you made the right call for your situation.

- Totally agree on felt breaking down fast - mine barely made it through two winters before it started cracking.
- Synthetic’s upfront cost was a stretch for me, but I figured fewer repairs would save money long run.
- Peel-and-stick looked tempting, but I just couldn’t justify the price for my small roof.
- One thing I noticed: synthetic can get slippery if you’re DIY-ing, so be careful up there.
- Curious if anyone’s had luck with the cheaper synthetics? Some brands seem way thinner than others...

- Used felt on my shed a few years back - cracked and curled after just one rough winter.
- Switched to a budget synthetic (don’t remember the brand, but it was thin) for my garage roof. It went down easy, but honestly, it felt almost like tarp material.
- Noticed it held up better than felt so far, but I’m not sure how it’ll do after a few more seasons.
- Agree about the slipperiness - almost wiped out when it got a little dew on it.
- For my climate (lots of freeze/thaw), I’d probably still pick synthetic over felt, even the cheap stuff... but I do wonder if the pricier brands are worth it.

I do wonder if the pricier brands are worth it.

That’s the million dollar question, right? I’ve put down both cheap and premium synthetics - honestly, some of the budget stuff does feel like glorified tarp, but it still outlasts felt in freeze/thaw cycles. The higher-end synthetics claim better UV resistance and tear strength, but I’ve seen them fail too if the install isn’t right. Sometimes you’re just paying for a name. If you’re not leaving it exposed for weeks, mid-range synthetic usually holds up fine. Anyone else notice some of those “grip” surfaces aren’t much better than regular plastic when there’s dew?

- I get the appeal of synthetics, but honestly, I’ve had old-school felt last 15+ years under asphalt in the Midwest - never had a leak until the shingles finally gave out.
- The “grip” thing is hit or miss. Some brands are slick as ice when wet, no matter what they claim.
- Pricey synthetics might be overkill unless you’re in a spot with crazy sun or wind. For basic jobs, felt’s still a solid bet if you’re not leaving it exposed.
- One thing - felt’s easier to patch if you ding it during install. Synthetics can tear weirdly and then you’re taping seams.
- Just my two cents... sometimes the old stuff works just fine.

Had a 12-unit building reroofed about 8 years ago - went with synthetic because the contractor swore by it. Honestly, it held up great during install (we had a few surprise storms), but I did notice that if you nick it with a shingle or tool, the tear can run a bit. Had to patch a couple spots with tape, which felt a little sketchy compared to just slapping another piece of felt on. On the other hand, I’ve managed properties with 20-year-old felt underlayment that only started leaking when the shingles were toast. Around here (Chicago area), felt seems to do just fine unless you’re leaving it exposed for weeks. Synthetic’s lighter, but I’m not convinced it’s always worth the extra cost unless you’re dealing with tricky weather or long exposure times.

On the other hand, I’ve managed properties with 20-year-old felt underlayment that only started leaking when the shingles were toast.

That lines up with what I’ve seen too - felt can be surprisingly resilient if it’s not left exposed for too long. Around Chicago, unless you’re dealing with a lot of wind-driven rain or big delays between tear-off and shingling, felt usually does its job just fine. The main thing I notice with synthetics is they’re great for those jobs where weather’s unpredictable and you might have to leave things open for a bit. But yeah, once you get a tear in synthetic, it can run pretty quick if you’re not careful. Tape patches always feel a little dicey to me too.

Did you notice any difference in how the roof “breathes” or handles condensation between the two? Sometimes I wonder if synthetic traps more moisture underneath, but I haven’t seen any hard evidence either way. Cost-wise, unless there’s a specific reason (like tricky slopes or long exposure), I’m with you - felt still makes sense for a lot of jobs. Curious if anyone’s had issues with synthetic getting brittle over time in cold climates?