- Humidity matters, sure, but honestly I think ambient temp is way more critical.
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Usually true, but too low can cause weak welds that fail later...seen it happen."starting at lower temps and gradually dialing up as you get comfortable is smart"
- Better to practice on scraps first, dial in your temp quick, then stick with it. Saves headaches down the road.
I see what you're saying about ambient temp being critical, but from my experience, it's not always as straightforward as dialing in a quick temp and sticking to it.
"Better to practice on scraps first, dial in your temp quick, then stick with it."
True in theory, but honestly, I've found that even after practicing on scraps, the roof itself can behave differently—especially if you're working on an older TPO membrane or one that's been sitting in the sun for a while. The material can react differently depending on age, cleanliness, or even subtle changes in the sun angle. Instead of locking myself into one temp setting, I prefer to periodically check weld quality as I go, adjusting slightly if needed.
I get the concern about weak welds from too low temps, but going too hot can cause brittleness or scorching that you might not notice until months later. It's a balancing act, really. Personally, I like to keep a scrap piece handy and occasionally double-check my welds as conditions change throughout the day...a bit tedious, sure, but cheaper than redoing the roof later.
Yeah, totally agree—TPO can be a finicky beast. I've had days where the morning welds were perfect, then by afternoon it was like welding bubblegum. Checking as you go is tedious, but beats getting called back later...ask me how I know, lol.
Yeah, TPO definitely has its quirks. I've found that once surface temps start creeping over 140°F, things get dicey real fast. The membrane starts acting gummy, and you end up chasing your tail trying to find the sweet spot on the welder settings. Had a job last summer where I swear the roof was hotter than my grill at home...ended up dialing back the heat and slowing down a bit. Tedious for sure, but saved me from another embarrassing callback, haha.
Interesting insights here, especially about dialing back the heat. Makes me wonder, is there a noticeable difference in weld strength or longevity when you're forced to slow things down and lower the welder temp? I've read mixed opinions on this—some say it doesn't matter as long as you get a good seal, others swear hotter and faster is always better. Curious if you've noticed any long-term differences on the roofs you've done this way...
