Glossy seams can definitely fool you sometimes. I've had jobs where the seams looked textbook-perfect—shiny, smooth, the whole nine yards—but after a year or two, they started lifting at the edges. Learned that glossiness alone isn't always reliable. Now I always do a quick probe test after cooling to double-check adhesion.
As for airflow, I used to think it didn't matter much either, but tweaking it slightly depending on ambient temps and wind conditions has saved me headaches. It's subtle, but worth experimenting with...
"Glossy seams can definitely fool you sometimes."
Yeah, totally agree with this. I've seen seams that looked showroom-perfect but failed way sooner than expected. Honestly, I think relying too much on appearance can lead us astray. Instead, I've found that dialing back the heat slightly and slowing down the weld speed helps achieve deeper, more consistent adhesion. Have you tried adjusting your welding speed along with airflow? Might be worth experimenting a bit more...
"dialing back the heat slightly and slowing down the weld speed helps achieve deeper, more consistent adhesion."
Interesting... but does slowing down too much risk overheating the material anyway? I'm no pro welder, just a homeowner trying to DIY without burning through my budget (or my roof, haha). From experience, finding that sweet spot between speed and heat has been tricky. Glossy seams fooled me once too—looked great, leaked like crazy during the first storm. Lesson learned the hard way. Any tips on balancing airflow without expensive gear?
You're definitely right about that balance being tricky—I've seen more than a few DIYers (and even some pros) struggle with overheating TPO by slowing down too much. The thing is, TPO has a pretty narrow temperature window where it welds nicely without scorching or weakening the material. If you slow down excessively, you're basically letting the heat gun linger too long in one spot, which can cause the membrane to become brittle or even burn through. The glossy seam issue you mentioned—yeah, that's a classic sign of overheating. It looks sealed, but really it's just melted on the surface without proper adhesion underneath.
As for airflow, that's actually a great point because it's often overlooked. You don't necessarily need expensive gear, but a steady and consistent airflow is key. I've seen guys rig up simple DIY airflow guides using aluminum flashing or even thin sheet metal scraps to direct the heat more evenly. It's all about consistent air distribution rather than having a fancy setup. Also, keeping your nozzle clean and free of debris helps maintain consistent airflow and temperature control.
Are you using a handheld heat gun or one of those walk-behind welders? Handhelds can be trickier since maintaining a consistent speed and angle is completely up to you. One trick I've found helpful is marking a test strip of scrap TPO with chalk or pencil lines spaced evenly apart, then practicing welding at different speeds and temperatures until the seams hold strong without glossing over. It takes some trial and error, but once you nail it down, you can replicate those settings across your whole roof.
Have you tried any kind of homemade airflow guide yet, or are you just winging it as you go?
I've been using a handheld heat gun myself, and yeah, keeping that steady pace is definitely the hardest part. I haven't tried making an airflow guide yet, but now you've got me thinking...might be worth rigging something up this weekend with some leftover flashing I've got lying around.
One thing I've noticed is that ambient temperature plays a bigger role than you'd think. Last summer I was welding seams on a hot afternoon, and even though my speed and temp settings were dialed in from practice runs, I still ended up with glossy spots. Had to dial back the heat quite a bit to compensate. So it's not just about your gear or technique—sometimes the weather throws you a curveball too.
I like your idea of marking test strips; wish I'd thought of that earlier. Would've saved me from redoing half my seams last year. Live and learn, right?
