I’ve got mixed feelings on the whole “synthetic never fails” thing. Maybe it’s just my luck, but I’ve seen a couple jobs where the underlayment started to wrinkle and even tear up after a few heavy storms—this was before the shingles even went on. Granted, both times the stuff sat exposed for way longer than intended because of weather delays, but still… it’s not bulletproof.
One project in particular, we had a combo of steep pitches and a bunch of valleys. The synthetic held up okay on the main runs, but around all those details, it just didn’t want to stay put once the wind picked up. Ended up patching more than I’d like to admit. Peel-and-stick is pricier, but man, on complicated roofs or places that get hammered by rain sideways, it’s been worth it for me.
I’m not saying synthetics are bad—just that they’re not all created equal, and sometimes the “good enough” stuff isn’t when you’re stuck waiting on a crew or the weather. Maybe it’s just Murphy’s Law at work, but I’d rather spend a little extra than have to explain to a client why their attic’s wet before we even get the shingles on.
- Had a similar situation last year—synthetic underlayment on a big duplex, and we got hit with two weeks of rain before the shingles could go on.
- Main sections were fine, but the valleys and edges started to curl up and even tore in a couple spots. Ended up with some water stains in the attic insulation... not fun explaining that to the owner.
- I’ve noticed the “premium” synthetics hold up better, but honestly, if there’s any chance of delays or bad weather, I just budget for peel-and-stick on the tricky areas now.
- It’s more upfront, but I’d rather pay for peace of mind than deal with repairs or complaints later.
- Noticed too that some crews don’t fasten the synthetic as well as they should, especially on steep slopes—makes a difference when the wind picks up.
- Guess it comes down to how long it’ll be exposed and how complicated the roof is. For simple jobs with quick turnaround, synthetic’s fine, but anything else... I’m with you, better safe than sorry.
Interesting you mention the valleys and edges—that’s exactly where I had trouble too, but I always wondered if it was more about how well the underlayment was installed than the material itself. I did a shed roof last fall with a mid-range synthetic (not the cheapest, not “premium” either), and after a week of rain, it held up alright except for a couple spots where I probably didn’t fasten it as tight as I should’ve. No leaks, but some curling at the edges.
I keep hearing about peel-and-stick being worth the extra cost for tricky areas, but does it really stick well if things get damp before shingles go on? Or does it just trap moisture underneath? I’m in a pretty humid area, so that’s my main worry. Also, are there any brands you trust more than others, or is it all about the install? Just trying to figure out if it’s worth upgrading or if careful install is enough.
Peel-and-stick is kind of a double-edged sword, at least in my experience. It’s a lifesaver in valleys and along eaves, but you’re right—humidity can mess with it if you’re not careful. I’ve seen it stick like glue even after a quick rain, but if the deck’s actually wet when you put it down, that’s when you risk trapping moisture. That can lead to some funky smells or even rot if it never gets a chance to dry out. I always try to wait for a dry stretch, but sometimes you just gotta roll with what the weather gives you.
Brand-wise, I’ve used Grace Ice & Water Shield and GAF’s WeatherWatch. Both held up, but honestly, the install made the biggest difference. If you get bubbles or don’t press it down tight, water finds a way. I’d say careful install is 80% of it, but for those tricky spots—valleys, chimneys, low slopes—peel-and-stick is worth the extra bucks. Just don’t skimp on prepping the surface, especially in humid spots. Learned that one the hard way...
Couldn’t agree more about install being the real make-or-break factor. I’ve seen even the “premium” peel-and-stick stuff fail when someone rushed it or skipped cleaning up dust and debris. Around here (humid summers, lots of storms), I’m honestly not a fan of using peel-and-stick across the whole roof. It’s overkill and, like you said, just asking for trapped moisture if you don’t get a bone-dry deck. Valleys, eaves, and around skylights? Absolutely—those spots need the extra protection.
I’d add that folks sometimes forget about compatibility with green roofs or solar installs. Some underlayments off-gas chemicals that can mess with membranes or plant roots. If you’re thinking about going green, look for low-VOC options—Grace is decent, but there are others out there now.
One last thing: don’t trust “self-sealing” claims too much. Staples or nails still need attention, especially if you’re in a freeze-thaw zone. Learned that lesson after a winter where the ice damming got real ugly...