- Totally get what you mean about the seams. I had a couple spots bubble up after a hot spell, even though the welds looked solid at first.
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— Yeah, I was surprised by this too. Used a cheap IR thermometer once and the roof was 30+ degrees hotter than the air.surface temp can be way higher than you’d guess just by feel
- Tried working in the shade with tarps—helped a bit, but not perfect. Still easier than fighting direct sun.
- Early morning is best for me, but sometimes you just gotta go when you can. Never realized how much sun could mess with TPO until now...
I’ve had the same thing happen—thought I nailed the seams, then a week of crazy sun and suddenly there’s bubbling. I’m curious, does anyone actually check the temp before starting? I just go by feel, but maybe that’s not enough. Wondering if it’s worth grabbing one of those cheap thermometers or if it’s overkill for a small job.
I just go by feel, but maybe that’s not enough. Wondering if it’s worth grabbing one of those cheap thermometers or if it’s overkill for a small job.
Honestly, I don’t trust the “by feel” method anymore. Did that last summer and ended up redoing half the seams after a heatwave. Those cheap IR thermometers aren’t perfect, but they’re better than guessing—especially when the sun’s baking everything. Even on a small patch, I’d rather spend $20 than risk peeling or bubbles down the line. Just my two cents...
- I tried the “by feel” thing too, but my hands are apparently not calibrated for roofing. Ended up with a couple seams that looked fine until the first rain, then… surprise, water feature in the living room.
- Grabbed one of those cheap IR thermometers off Amazon after that. Not super fancy, but at least it tells me if I’m way off. I figure if I’m already sweating buckets up there, might as well know if the roof’s about to melt.
- My patch job was only like 6x6 feet, so I get the hesitation on buying more gadgets. But honestly, $20 is less than what I spent on pizza for the “roofing crew” (aka my brother-in-law and his appetite).
- Only thing is, sometimes the thermometer reads way higher than what the manual says is “safe” for welding TPO. Like, sun hits that white membrane and suddenly it’s 160°F before I even turn on the heat gun. Anyone else run into that? Do you just wait for clouds or go for it anyway?
- Also, does anyone actually trust those little temp strips they sell at Home Depot? I stuck one on and it just turned black instantly… not sure if that means “perfect weld” or “congrats, you’ve invented lava.”
- For what it’s worth, my neighbor swears by the “if you can’t touch it for more than 2 seconds, it’s too hot” rule. But he also thinks duct tape fixes everything, so… grain of salt.
Curious if anyone’s had luck welding TPO in direct sun without things bubbling up later. Or is it just a lost cause unless you start at sunrise?
- I tried welding TPO in direct sun last summer and yeah, the temp shot up way faster than I expected. My cheap IR thermometer said 170°F before I even plugged in the heat gun, which seemed wild.
- Ended up waiting until after dinner a couple days—way less glare and the surface cooled down a lot. Still wasn’t perfect, but at least it didn’t bubble like when I tried at noon.
- Those temp strips? Mine just turned black too, which honestly made me laugh. Felt like there’s no in-between: either it’s “not hot enough” or “molten plastic.”
- My neighbor swears by the “if you smell burnt marshmallow, you’ve gone too far” trick. Not super scientific but… kinda worked for me? No leaks so far (knock on wood).
- Honestly, early morning or late evening seems safest if you’re not a pro. Sun + white TPO = way hotter than you’d think.
Wouldn’t call it a lost cause, but I definitely learned not to trust my instincts (or my brother-in-law’s advice) with this stuff.
