Why some roof coatings actually make things worse

If you’re not 100% sure it’s bone dry, you’re just sealing in problems.

That hits the nail on the head. I’ve lost count of how many times I’ve seen bubbling or peeling on a “freshly coated” roof just because someone rushed the prep. Folks see those slick ads and think a miracle coating will fix rot or leaks, but it’s really just putting a lid on top of whatever’s underneath - good or bad.

I do agree about breathable membranes being a smarter move, especially on older homes where moisture is already an issue. It’s tempting to go for the quick fix, but in my experience, those coatings can actually trap water and speed up wood rot or mold. One job I checked out last year, they’d coated over some damp decking and by spring, the whole thing was soft underfoot… ended up costing way more than if they’d just replaced the trouble spots first.

Not saying coatings are always bad - they have their place - but skipping steps or ignoring what’s under the surface is asking for trouble. Sometimes spending a bit more upfront saves you from bigger headaches down the line.

Not saying coatings are always bad - they have their place - but skipping steps or ignoring what’s under the surface is asking for trouble.

Couldn’t agree more. I’ve seen folks slap on a “miracle” coating thinking it’ll solve everything, but if there’s moisture hiding underneath, you’re just making a petri dish for rot. Had a neighbor who tried to save money by coating over some old cedar shakes - looked great for a few months, then the whole thing started sagging and stinking like wet mulch. Ended up ripping it all off and going with a green roof system instead.

Breathable membranes make a world of difference, especially in damp climates. They let moisture escape instead of trapping it, which is huge if you’re dealing with older wood or questionable decking. I get why people want quick fixes, but honestly, nothing beats taking the time to check what’s really going on under there. Sometimes you gotta bite the bullet and do some demo before you build back up. It’s not as flashy as a new coating, but in the long run, it’s way less hassle.

That’s a good point about the quick fixes. I looked into coatings when I bought my place last year, mostly because the idea of just rolling something on and being done sounded pretty appealing. But after poking around in the attic and seeing some old water stains, I figured it was smarter to get a roofer to check for hidden damage first. Turns out there was some soft decking under one corner - nothing major, but enough that a coating would’ve just trapped the problem.

I ended up going with a breathable underlayment and new shingles instead of a coating. Cost more up front, but I sleep better not worrying about mold or rot sneaking up on me. I get why people want to save money, but sometimes those shortcuts just make things worse (and more expensive) in the long run.

Funny thing is, my neighbor did the opposite - put a fancy white coating on his flat roof and now he’s dealing with leaks around the skylight. Guess there’s no substitute for actually checking what’s under the surface before you cover it up...

Couldn’t agree more about checking under the surface first. I’ve seen folks slap on a coating thinking it’ll solve everything, but if there’s even a little rot or moisture trapped underneath, you’re just asking for trouble. Like you said,

“sometimes those shortcuts just make things worse (and more expensive) in the long run.”

Seen this a lot, especially on older homes around here. Folks think a fresh coat will fix leaks, but if the decking’s soft or there’s hidden moisture, you’re just sealing in the problem. Had a job last fall - customer wanted a quick coating over some “minor” leaks. Pulled up the old material and half the plywood was mush. Ended up costing way more than if they’d dealt with it early. Sometimes you just can’t shortcut the prep work, no matter how tempting it is.

I get where you’re coming from, but I’ve actually had decent luck with coatings - at least as a stopgap. My place is a 1950s ranch, low slope, and I used an elastomeric coating on a small section that started leaking mid-winter. It bought me a year until I could budget for a full tear-off. Not saying it’s a fix for rotten decking, but sometimes you just need to buy time, especially if the weather or money isn’t cooperating. Just gotta know what you’re covering up, I guess.

- Totally get the need for a stopgap, especially mid-winter.
- Just a heads up - sometimes coatings can trap moisture if there’s hidden rot or leaks underneath.
- Seen a few cases where folks thought they were buying time, but ended up with worse decking damage later.
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“Just gotta know what you’re covering up, I guess.”

Had a situation last year with one of our older flat roofs - mid-February, snow everywhere, and a leak started right over a tenant’s kitchen. We went with a quick elastomeric coating just to get through the season. Looked fine at first, but by spring, when we finally got the chance to pull things up, there was way more rot than we expected. Turns out water had been seeping in from a split seam for months, and the coating just locked it all in.

I get why folks use coatings as a temporary fix (sometimes you just don’t have another option in winter), but I learned the hard way that if you’re not 100% sure what’s going on underneath, it can backfire. Now I always try to check for soft spots or weird smells before sealing anything up - even if it means cutting out a little section to peek under. Sometimes feels like overkill, but it’s saved us from bigger headaches down the line.

Not saying coatings are bad - they’ve definitely bought us time before - but yeah, you really gotta know what you’re covering up.

I get where you’re coming from, but I’ll be honest - sometimes you just gotta slap a coating on and cross your fingers, especially in the dead of winter. I’ve seen more than a few roofs where poking around for soft spots in February would’ve meant turning a small leak into a full-blown indoor waterfall. Not ideal, but when you’re dealing with 20-year-old torch-down and the snow’s piled up, options get real limited.

That said, I do agree that coatings can be a double-edged sword. I’ve seen folks treat them like magic paint that’ll fix anything, and then act surprised when the rot fairy pays a visit in spring. But I’ve also had jobs where a quick elastomeric bought us enough time to plan a proper tear-off once the weather warmed up. It’s all about knowing your roof’s history and not pretending a bucket of goop is a miracle cure.

If you’re dealing with chronic leaks every winter, though, might be time to bite the bullet and budget for a real fix. Coatings are like duct tape - great in a pinch, but you wouldn’t want to build a house out of it.

I totally get the urge to just slap on a coating and hope for the best when it’s freezing and you’re staring down another leak. Sometimes you really don’t have much choice, especially with older roofs and a foot of snow up there. But I do wonder - how many folks actually check what’s under the surface before rolling on that elastomeric stuff? I’ve seen situations where a “quick fix” ended up trapping moisture, and come spring, the whole assembly was way worse off.

On the other hand, I’ve also seen a well-timed coating buy a few extra months until you can get a real crew up there. I guess my main question is, are people checking compatibility with their existing roof system? Not all coatings play nice with torch-down or old asphalt, for example. Plus, if you’re in a spot with big temp swings, some of those cheaper coatings just crack right off.

Personally, I’ve had better luck with reflective coatings in the summer for energy savings, but I’m always a little nervous about masking bigger problems underneath. Anyone else ever peel back a coating in spring and find a science experiment growing under there?

Had to laugh at the “science experiment” bit - been there, unfortunately. Last winter I got desperate and rolled on a cheap acrylic coating over my old low-slope asphalt roof. Didn’t check for trapped moisture, just wanted to stop the drip above my laundry room. Come spring, I peeled back a section and found black mold and some weird fuzzy stuff growing underneath. The coating had basically sealed in all the wetness from snow melt, so nothing dried out.

What I learned: quick fixes are tempting but risky if you don’t know what’s going on under the surface. Now I always do a few things before putting anything down: 1) Check for soft spots or bubbling - usually means water’s already in there; 2) Try to dry things out as much as possible (even if it means waiting for a warm day); 3) Double-check that the coating actually works with whatever roofing material is up there. Found out some coatings just won’t stick right to old torch-down.

It’s not always easy when you’re on a tight budget, but skipping those steps cost me more in cleanup later. Sometimes holding off until you can do it right is worth it, even if it means another bucket under the leak for a while...

Totally get where you’re coming from - been burned by quick fixes myself. A couple things I’d add:

- Coatings can actually trap more heat, which makes any trapped moisture worse (especially with black roofs in summer).
- If you ever go the coating route again, those elastomeric or silicone ones are more forgiving, but still gotta be bone dry underneath.
- Green roofs (even small DIY ones) can help with drainage and insulation, but they’re a bigger upfront project.
- Sometimes just patching leaks with flashing or membrane is less risky than a full roll-on.

It’s tough waiting out a leak, but yeah, rushing it usually bites back...

Yeah, I learned the hard way that slapping a coating on top of a damp roof is just asking for trouble. Did it once on my old garage - looked great for about two months, then the bubbling started and it smelled like wet socks every time the sun hit it. Ended up tearing it all off and trying a tiny green roof patch instead. Way more work upfront, but honestly, my garage is cooler in summer now and no leaks so far. Not saying it’s for everyone, but if you’re already ripping stuff up, might as well try something different...

Yeah, putting any kind of coating over a damp roof is just asking for headaches. I’ve seen bubbling and peeling more times than I can count - usually ends up trapping moisture and making the whole problem worse. What’s worked for me is always making sure the surface is bone dry before even thinking about coatings. If you’re not 100% sure it’s dry, wait it out or use a fan. The green roof patch idea’s cool though - never tried it myself but I’ve heard it can help with heat, like you said. Just takes a lot more prep and maintenance, from what I hear.

- Agree on the dry surface - never had a coating last when there was hidden moisture.
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“I’ve seen bubbling and peeling more times than I can count - usually ends up trapping moisture and making the whole problem worse.”

Coatings are only as good as what’s underneath.

That’s exactly what happened with my garage roof last year. I figured a thick elastomeric coating would buy me a few more seasons, but I didn’t check for soft spots first. Ended up trapping moisture, and the plywood just crumbled in places. Now I’m way more careful - step one is always poking around for any give or weird smells, then I use a cheap pin-type moisture meter before even thinking about coatings.

I’m curious - has anyone tried those “liquid rubber” products on older roofs? I keep seeing ads, but I’m skeptical. Seems like if the base is even a little compromised, it just seals in the problem. Also, for anyone with green roofs, how do you handle drainage? I love the idea, but the maintenance sounds like a full-time job. Maybe it’s just not worth it unless you’re really into gardening... or am I missing something?

That moisture trap thing is no joke - I learned the hard way too. Thought I was being clever with a “quick fix” coating, but yeah, all it did was turn my sheathing into what I can only describe as soggy cardboard. Those liquid rubber ads look tempting, but I’m with you - if there’s any rot or softness, it just locks in the mess. As for green roofs, I love the concept, but honestly, my thumbs are more brown than green... The drainage setups seem like a science project. If you’re not into regular upkeep, it might be more hassle than it’s worth.

I get where you’re coming from about green roofs looking like a science experiment - my first attempt was a mess. I underestimated how much water would pool up before I got the drainage right, and it nearly turned into a rooftop swamp. Still, once I figured out the layers (and picked plants that don’t mind a little neglect), it’s been surprisingly low-key. Curious if you ever looked into those modular tray systems? They seem less intimidating than the full-on build, but I wonder if they actually drain better or just shift the problem around.

I hear you on the swampy roof phase - been there, had to rip out a whole section after some surprise pooling. The drainage piece is where most people trip up, honestly. Those modular trays look appealing, especially for folks who don’t want to commit to a full build-up, but I’m not convinced they solve the core issues. From what I’ve seen, they can make maintenance easier since you can swap out sections if something goes wrong, but sometimes water just gets trapped between the trays and the membrane underneath.

I’ve also noticed some of those systems rely on pretty shallow soil, which limits what you can grow - sedum does fine, but if you want anything with deeper roots, it’s tricky. Have you noticed any difference in how your setup handles heavy rain? Around here (Midwest), we get those sudden downpours and even with a decent slope, things can get dicey.

Props for sticking with it though. Most folks give up after the first mess. It’s always a balancing act between making it low-maintenance and not causing more headaches down the line.