I tried patching a small section of TPO last August, thinking I’d just get it done before work. Big mistake. The membrane was already hot to the touch at 9am, and by the time I got the heat gun out, it felt like I was fighting against goo.
—that’s exactly what happened to me. I didn’t have an IR thermometer, so I just went by feel, but now I’m realizing that wasn’t smart. If I had to do it again, I’d definitely wait for a cooler day or at least try early morning. It’s wild how much the sun changes things.“the seams looked like melted marshmallows”
“the seams looked like melted marshmallows”
That’s a pretty accurate description, but honestly, I don’t think waiting for a cool day is always the answer. I’ve patched TPO in the middle of July (Texas, no less), and yeah, it was a sweaty mess, but if you keep the heat gun on the lowest setting and move quick, you can still get a solid weld. The trick for me was having a big piece of cardboard to kneel on—saves your knees and keeps you from sticking to the roof. Not saying it’s fun, but sometimes you just gotta work with what you’ve got, sun or not.
I get where you’re coming from, but I’ve seen too many welds fail later when folks try to rush it in extreme heat. Surface temps on a white TPO roof can hit 160°F or more in direct sun—add a heat gun and you’re flirting with overcooked seams, even on low. I’ll sometimes throw a tarp up for shade or work early mornings just to keep things manageable. Not saying it can’t be done, but I’d rather take a little extra time than risk callbacks down the road.
I’ve run into this exact thing during a couple inspections—usually after a summer install. I remember one job where the seams looked perfect at first glance, but when I poked around with my probe, a few spots just peeled right up. The owner said it was welded in July, mid-afternoon, and the crew was hustling to finish before a storm rolled in. Classic case of what you mentioned:
“Surface temps on a white TPO roof can hit 160°F or more in direct sun—add a heat gun and you’re flirting with overcooked seams, even on low.”
In my experience, those “overcooked” seams can look fine for months, then start to fail once the weather swings or the building shifts a bit. I get why folks want to push through, but honestly, I’d rather see a slower job with some shade or early morning work than have to write up another failed seam in my report. It’s one of those things where patience really does pay off, even if it means dragging out the schedule a little.
- Had a crew do my TPO last August—midday, full sun. They were sweating buckets and the roof felt like a frying pan.
- I asked if that was normal and got a shrug... but now I’m wondering if those seams are gonna hold up through winter.
- Is it really that risky to weld when it’s blazing out? Or is it just about taking your time?
- Kinda wish they’d started at sunrise, but I get wanting to beat the rain.
- Anyone else notice seams looking fine until the first cold snap? That’s when mine started to look a little sketchy.
