Yeah, the midday sun is brutal on TPO—I've made the same mistake thinking I could just “get it done” before it got too hot. The membrane gets way too soft and you end up chasing your welder settings all over the place. In my experience, anything above about 85°F ambient temp and that roof surface is probably already pushing 120°F or more. Even if you dial back the welder, it's hard to get a solid bond without overheating or stretching the material. I’ve tried the heat gun trick too, but honestly, it never felt consistent enough for me. Early morning or cloudy days really are the way to go... patience definitely pays off with this stuff.
I’ve definitely noticed the same thing—once that membrane starts feeling like warm taffy under your boots, it’s game over for clean welds. I tried working through a lunch break once, thinking I could just tweak the welder and power through... ended up with seams that looked like they’d been chewed on. For me, if my hand can’t rest on the roof for more than a second or two, I just call it and wait for things to cool off. Early mornings are way less stressful, and you don’t end up fighting the material every step.
For me, if my hand can’t rest on the roof for more than a second or two, I just call it and wait for things to cool off.
That’s pretty much my rule too. If the membrane’s so hot you can’t touch it, you’re just asking for trouble. Ever tried using an IR thermometer? I started bringing one after a few botched seams—if the surface temp’s pushing 130°F or higher, I just don’t bother. Curious if anyone’s managed decent welds above that, but for me, it’s not worth the wasted material. Early mornings or cloudy days make life way easier.
I’ve tried pushing through on a hot day, thinking I could outsmart the sun, but honestly, the seams just turned out sloppy. Even with the gun dialed down, the membrane got gummy and weird. IR thermometer’s a game changer—wish I’d started using one sooner. Anything over 130°F and my welds get sketchy fast.
Totally agree, that sun can be brutal. I tried welding TPO on a July afternoon—thought I was saving time, but the seams looked like melted marshmallows. Even with the heat gun on low, the membrane just got sticky and stretched out weird. IR thermometer’s been my secret weapon lately too. For me, once the surface temp hits around 125°F, things start to go sideways fast. Shade cloths or starting at sunrise helped a bit, but honestly, sometimes it’s just not worth fighting the heat.
