Trying to decide between beefing up the underlayment beneath my clay tiles, or just going with a high quality sealant over the top. Anyone find one way works better long-term? My neighbor swears by underlayment but it’s pricier. What’s your experience?
Trying to decide between beefing up the underlayment beneath my clay tiles, or just going with a high quality sealant over the top. Anyone find one way works better long-term? My neighbor swears by underlayment but it’s pricier. What’s your experience?
I've worked on a lot of tile roofs—mostly in coastal areas where we get a fair amount of wind-driven rain—and I’ve seen both approaches in action. Here’s what I’ve noticed over the years.
Sealants can be tempting because they’re less invasive and you see quick results. But honestly, I’d call them more of a stopgap than a real solution. Even the best sealants break down from UV exposure and temperature swings, especially if you’re somewhere that gets hot summers or freezing winters. I’ve been called back to jobs where a “high quality” sealant lasted maybe three years before leaks started showing up again. It’s also tough to get consistent coverage around overlaps and fasteners, so water finds its way in eventually.
Now, about underlayment: Yes, it costs more upfront and takes more labor, but it’s really your primary waterproofing layer under tile. The tiles themselves shed most water, but wind-driven rain or cracked tiles will let some through—that’s where underlayment earns its keep. I’ve torn off 20-year-old tile roofs where the original synthetic or double-layer felt was still holding up, even after some tiles had cracked or shifted. If you’re already re-roofing or have access to the deck, upgrading the underlayment is hands-down the better investment for longevity.
One thing I’ve seen people overlook: if your roof has a low pitch or gets tons of debris (like from overhanging trees), you might need an even beefier underlayment system—sometimes self-adhered membranes in valleys or along eaves.
I get that cost is a factor. But if you’re planning to stay in the house long-term, or just want peace of mind during storm season, I’d lean toward investing in good underlayment now rather than patching with sealant every few years. If you’re just dealing with a small area and not ready for a full redo, then sure—a sealant might buy you some time.
Just my two cents from crawling around on too many old tile roofs...
Even the best sealants break down from UV exposure and temperature swings, especially if you’re somewhere that gets hot summers or freezing winters.
Couldn’t agree more—sealants just don’t hold up long-term, especially if you get wild weather swings. I’ve seen folks spend more patching leaks every couple years than they would’ve dropping cash on solid underlayment once. If you’re already pulling up tiles, might as well do it right and not have to stress every time a storm rolls in.
Yeah, I’ve seen that too—people get stuck in this cycle of patching and re-patching, and it’s like playing whack-a-mole with leaks. Sealant’s great for a quick fix, but if you’re living somewhere with wild weather (I’m in the Midwest, so we get tornadoes one week and snow the next), it just doesn’t last. I tried the “just seal it” route on my uncle’s place last year, and by the time spring rolled around, we were back up there with a caulk gun, cursing at the squirrels and the sun.
If you’re already pulling up tiles, I’d say it’s the perfect time to go all-in with a solid underlayment. It’s a pain to do, sure, but way less of a headache than climbing up there every time it rains. Plus, you get to skip the “surprise drip on your forehead at 2am” experience. Not that I’m speaking from personal experience or anything… (okay, maybe I am).
One thing I’d add—if you’re in a spot where it gets super humid, make sure you’re using underlayment that can handle moisture. Some of the older felt stuff just turns into mush after a couple of hot summers. I’ve seen synthetic underlayment hold up way better, but it does cost a bit more. Still, cheaper than replacing soggy drywall or dealing with mold.
Long story short: sealant’s like putting a band-aid on a leaky pipe. Underlayment’s more like actually fixing the pipe. Might take more work up front, but your future self will thank you.
I’ve inspected a decent number of tile roofs over the years, and honestly, I’ve seen the same thing play out: folks try to save a few bucks by just slapping on sealant, and it almost always ends up being a temporary fix. It’s kind of like using duct tape on a leaky garden hose—fine for a week or two, but eventually you’re back to square one. Especially if you’re in an area that gets hard rain or big temperature swings, sealant tends to crack or peel way sooner than people expect.
That said, I totally get the sticker shock with underlayment—especially the newer synthetic stuff. But when you look at it over the lifespan of the roof, it’s usually cheaper in the long run. The old felt underlayments can definitely get gross and start to rot if there’s any trapped moisture, so I’d lean toward synthetic if you can swing it. It’s lighter, tougher, and doesn’t absorb water like felt does.
One thing I’d watch for is ventilation under those clay tiles. If your attic isn’t breathing right, moisture can build up from inside the house too, not just from leaks. I’ve seen mold issues pop up in houses that technically never had a “leak” from outside—just condensation and poor airflow.
Last thing—if you do end up going with underlayment, check what your local code requires. Some places are picky about what type you use under tile. And if you’re hiring someone, ask about their warranty on both materials and labor. I’ve seen a few jobs where the installer cut corners on the underlayment and it came back to bite the homeowner a couple years later.
Anyway, I’d be curious if anyone’s had luck with those newer “liquid membrane” products as an alternative to traditional underlayment? Haven’t seen them much in my area but maybe they’re catching on somewhere else.
