I’ve seen some wild stuff on summer inspections—guys trying to weld TPO at noon, sweating buckets, and the seams end up looking like burnt toast. I always tell folks, if your boots are sticking to the membrane, it’s probably too hot for a clean weld. Early morning’s definitely easier on the eyes, but yeah, that dew can turn things into a slip-n-slide. Pull test is my go-to too... numbers only tell half the story.
Yeah, I’ve tried welding TPO in the middle of a July afternoon and it was a mess. The seams just wouldn’t bond right, and I ended up redoing half of them the next morning. I get what you mean about the boots sticking—once you feel that, it’s probably time to pack it in for a bit. Early mornings are better, but that dew is no joke either. I nearly wiped out stepping onto a wet patch last summer.
I’ve found that if the surface is too hot to touch for more than a second, it’s just not worth trying. The welds look okay at first but start peeling after a few months. Pull tests help, but sometimes you can just tell by looking at the seam if it’s cooked or not. I wish there was a magic number for “too hot,” but honestly, it seems like you’ve got to go by feel and experience more than anything else.
I wish there was a magic number for “too hot,” but honestly, it seems like you’ve got to go by feel and experience more than anything else.
That’s been my experience too—sometimes you just know when it’s not going to work, no matter what the thermometer says. I’ve seen crews try to push through the heat and it always ends up costing more in repairs later. Trusting your gut (and your boots sticking) is underrated.
I’ve watched more than one crew try to “beat the clock” on a hot day, thinking they could outsmart the sun. Never seen it end well. Last summer, my neighbor’s guys tried welding TPO when it was pushing 100 out—membrane got all gummy, seams looked fine at first, but a month later, bubbles everywhere. I get wanting to finish the job, but sometimes you just gotta call it and wait for better weather. Thermometers are nice, but melted sneakers tell the real story.
I’ve tried patching TPO on my own garage roof in July, and let’s just say I learned the hard way that “too hot” is a real thing. I figured if I started early, I’d beat the heat, but by 10am the membrane was already soft and sticky. My seams looked okay at first, but a couple weeks later, I noticed some spots lifting and a few small bubbles. Ended up redoing those sections in the evening when things cooled off.
Here’s what I do now:
1. Check the forecast—if it’s over 90, I just wait.
2. If I have to work, I start at sunrise and stop by mid-morning.
3. I always touch the membrane—if it feels like it’s burning my hand, it’s too hot for welding.
4. I keep a cheap infrared thermometer handy, but honestly, my shoes melting to the roof is a better warning.
I get wanting to finish a job, but rushing it in the heat just means you’ll be back up there fixing it later. Learned that lesson the sweaty way...
