You're definitely not alone on this. I've noticed the same thing when doing my own roof last summer—some days everything would go smooth as butter, and other times it felt like I was fighting the seams every step of the way. Honestly, humidity and temperature swings seemed to make a huge difference for me.
For example, I was welding TPO on a pretty humid afternoon, and no matter how careful I was with my settings, the seams just wouldn't lay down right. They'd bubble up or get wavy, even though I hadn't changed anything from the day before. At first, I thought I was losing my touch...but then a buddy of mine who does roofing professionally mentioned he sees the same issues when it's overly humid or extremely hot. According to him, high humidity can trap moisture between layers, causing bubbles or uneven welds. And when it's scorching hot outside, the membrane itself can soften too much, making it tricky to get a clean weld without distortion.
What helped me was picking cooler mornings or late afternoons to do most of my welding. I'd also keep an eye on humidity forecasts—if it was extra muggy out, I'd try to avoid doing seams altogether that day. Not always convenient, but it saved me a lot of headaches.
Bottom line: don't beat yourself up over it. Weather plays a bigger role than most people think. Sometimes you can do everything perfectly and still face challenges because of conditions beyond your control...just part of the roofing game, I guess.
I've run into similar issues myself. Last year, I was welding TPO on a particularly hot day—must've been close to 95°F—and noticed the membrane was getting way too soft. Even dialing down the heat settings didn't help much. The seams ended up wavy and uneven, and I had to redo a good chunk of it later.
I started paying closer attention to surface temps rather than just air temps. Using an infrared thermometer, I found that the membrane surface could easily hit 140°F or higher on sunny days, even if the air temperature was lower. After some trial and error, I found that once the membrane surface got above about 130°F, welding became noticeably trickier. Now I try to schedule welding for early mornings or cloudy days whenever possible.
Humidity definitely plays a role too, but in my experience, surface temperature seems to be the bigger factor with TPO. Curious if anyone else has measured surface temps and found a similar threshold?
I've never measured exact surface temps, but I've definitely noticed welding gets messy on hot, sunny afternoons. Maybe that's why my seams always look better when I'm out there early... guess I'm not just imagining things, huh?
You're spot on about the afternoon heat messing things up. I've noticed the same thing when patching my own roof last summer. I'd planned to knock it out quickly in the afternoon, but the heat made the welds look sloppy and inconsistent. Ended up redoing half of it the next morning when it was cooler, and it went way smoother. Definitely better to get an early start if you want cleaner seams.
Yeah, heat definitely complicates things. Have you noticed if humidity plays a role too? I've found that even moderate temps with high humidity can make the seams tricky and less consistent... curious if anyone else has experienced that.
