"Older TPO that's been sitting exposed for a while seems to need a slightly different approach—sometimes lower heat but slower passes."
Interesting point, but I've actually found the opposite works better for me. With older membranes, I've had more success bumping the heat slightly higher and moving quicker. Seems counterintuitive, I know, but it helps avoid overheating and warping the material. Every roof's a bit different though...guess that's why scrap testing is key. Haven't tried vegetative roofs yet, but sounds intriguing.
Funny you mention vegetative roofs—I once had a contractor joke that welding TPO on those is like grilling veggies: too hot and they're toast, too slow and you're left with soggy lettuce. 😂
But seriously, I get what you mean about higher heat and quicker passes. Had one older roof last summer where I tried low-and-slow first, thinking I'd baby it a bit...ended up looking like a melted ice cream sandwich. After some head-scratching (and mild swearing), found that nudging the heat up slightly and moving faster gave me cleaner seams without warping.
Guess there's no universal recipe for this stuff—every membrane seems to have its own quirks. Definitely agree with scrap testing though; better to sacrifice a few scraps than risk turning the whole roof into abstract art.
Had a similar experience myself when I tackled my garage roof last spring. Thought I'd play it safe with lower heat, but ended up with seams that looked more like melted cheese than a clean weld. After some trial and error (and a few scraps sacrificed), I found bumping the temp up just a bit and speeding up my passes made all the difference. Definitely agree—each membrane seems to have its own sweet spot, and scrap testing is your best friend here.
Had a similar issue myself—went too cautious initially and ended up with seams that barely bonded. Curious though, did you notice ambient temperature affecting your sweet spot? I found cooler mornings required nudging the heat slightly higher to get consistent welds.
Good point on ambient temps affecting welds—definitely noticed that myself. A few things I've picked up over time:
- Cooler mornings mean denser, stiffer TPO membrane; slightly higher heat helps soften it up.
- Keep an eye on wind chill too... subtle but makes a difference.
- Trial welds are your friend; quick test strips help dial in the sweet spot before committing.
Sounds like you're already getting a feel for it though... keep at it, you'll nail down that balance soon enough.
