I do think you’re right about synthetic holding up better if there are delays, but I’ve also seen some cheaper rolls that looked rough after just one summer.
That’s been my experience too—some of the bargain synthetics are almost as bad as felt once the sun bakes ’em. I’ve torn into roofs where the underlayment just crumbled in my hands, felt or cheap synthetic, didn’t really matter. Ventilation’s a big one folks overlook... seen more than a few “30-year” roofs barely make it to 15 because the attic was basically an oven. Around here (Indiana), I usually lean toward mid-range synthetics, but I’m still waiting for one to actually live up to those wild lifespan claims.
Ventilation’s a big one folks overlook... seen more than a few “30-year” roofs barely make it to 15 because the attic was basically an oven.
That part really hits home for me. I manage a few duplexes in central Indiana, and honestly, I’ve seen more damage from poor attic airflow than from the underlayment itself. Had a place with a “lifetime” synthetic that started curling and cracking after six years—turns out the attic vents were clogged with insulation and dust. The shingles weren’t even the main problem.
I’ve also noticed the cheaper synthetics don’t seem to handle sun exposure much better than felt. One summer of direct sun while waiting on shingles and it’s already brittle. The mid-range stuff is better, but I still wouldn’t trust it for more than a couple weeks uncovered. I get why folks go for the budget rolls, but it’s a gamble if there are any delays.
One thing I do like about synthetics is they’re lighter and easier to handle, especially on steeper roofs. Felt always seems to tear if you look at it wrong, but at least you know what you’re getting—no wild claims about lasting 50 years.
At this point, I’m not convinced any underlayment will last as long as the packaging says, unless everything else (ventilation, install, flashing) is perfect. Around here, the weather’s just too unpredictable. I’d rather spend a bit more upfront and not have to worry about it for a while, but I’m still waiting for one to really impress me.
At this point, I’m not convinced any underlayment will last as long as the packaging says, unless everything else (ventilation, install, flashing) is perfect.
I get where you’re coming from, but I’ve actually seen some of the higher-end synthetics hold up surprisingly well—even with less-than-ideal ventilation. After a hailstorm last year, we tore into a 12-year-old roof with synthetic underlayment and it was still flexible, no brittleness at all. Felt on similar jobs was usually half gone or stuck to the decking. Maybe it’s just luck or brand differences, but I wouldn’t write off all synthetics yet.
I’ve actually seen some of the higher-end synthetics hold up surprisingly well—even with less-than-ideal ventilation.
That’s interesting—you’re making me rethink my assumptions. I’ve always heard from the old-timers that felt is just “what you use” and anything else is asking for trouble, but I’m starting to see why synthetics are getting more popular. We did a tear-off on a 15-year-old roof last month, and the felt was basically glued to the plywood, all crumbly and stuck. The homeowner said they had decent ventilation, too.
But then, a neighbor had synthetic underlayment put down about the same time, and when they replaced their shingles, the stuff was still in one piece. No idea what brand it was, but it didn’t look brittle or anything. Maybe it really does come down to which synthetic you use—and how careful the install is.
I still wonder about the long-term, like 20+ years. Has anyone actually seen synthetic last that long, or is it too new for that?
That’s basically what I’m wondering too. I’ve always heard felt is tried-and-true, but seeing synthetic hold up that well after 15 years is making me question if it’s worth the extra cost. Hard to know until more time passes, I guess.