I always touch the membrane—if it feels like it’s burning my hand, it’s too hot for welding.
That’s pretty much my “scientific” method too. I learned the hard way last summer when I tried to save a few bucks by patching my shed roof at noon—ended up with more blisters on my hands than seams on the TPO. Now, if the weather app says 90+, I just call it a Netflix day. The thermometer is handy, but honestly, if I’m sticking to the roof like Velcro, it’s time to bail.
I hear you on the “hand test”—I’ve done the same, but after one too many scorched palms, I started using an infrared thermometer. Not super fancy, just one of those $20 ones from the hardware store. It’s not perfect, but at least I know when the surface is pushing 130°F, it’s time to pack it in. I tried pushing through once in July and the seams looked like melted cheese... lesson learned. Sometimes it’s just not worth the risk (or the sunburn).
I tried pushing through once in July and the seams looked like melted cheese... lesson learned.
Been there—nothing like watching your seams ooze apart to make you rethink your approach. I used to rely on the “it feels hot enough” method, but after seeing TPO bubble up like a pizza, I switched to an IR thermometer too. For me, once the surface temp hits 120°F or so, it’s just not worth fighting the material. Even with shade tents, the welds can get sketchy. Sometimes you just gotta call it and wait for a cooler window.
- Seen a lot of TPO jobs go sideways in the summer. Once that rooftop temp climbs, you’re fighting a losing battle.
- IR thermometer’s a must—surface can be way hotter than the air. I’ve clocked white TPO at 140°F+ on a sunny day, even when it’s only 90 out.
- In my experience, anything over 110-115°F surface temp and you start risking weak welds or that “cheese” effect. Even if you get it to stick, long-term durability takes a hit.
- Shade tents help a bit, but not enough if the deck’s already baking. Sometimes you just have to pack it up and come back early morning or after a cloud roll-in.
- I’ve seen crews try to push through with extra fast passes or cranking down the heat gun, but that usually ends up worse—burns or cold welds both show up later in inspections.
- If you’re stuck working in heat, test-weld scraps every hour or so. It’s not perfect, but better than guessing.
- Not worth risking callbacks or warranty headaches just to finish in one shot. Sometimes waiting is the best call, even if it means rescheduling.
I’ve run into this a bunch during summer inspections—those TPO seams can look fine at first glance, but if you dig a little deeper (literally, sometimes with a probe), you’ll find spots that just didn’t bond right. I’m with you on the IR thermometer. I’ve seen readings that made me double-check the device... 135°F on a white roof when the air temp was barely pushing 90. Wild.
Curious if anyone’s had luck with those reflective tarps or temporary coatings to drop the surface temp a few degrees? I’ve seen a couple crews try it, but can’t say I’ve noticed a huge difference during follow-up inspections. Also, has anyone actually seen a manufacturer back up a warranty claim when welds fail due to high temp installs? I’ve heard stories, but in practice, it seems like it always comes back on the installer.
I get the urge to push through and finish, but man, callbacks are a pain for everyone. I’d rather see a job delayed than have to write up a report on failed seams six months later.
