Had a job last month where the thermal scan looked like something out of Predator—except it missed half the leaks. Flat roof, two layers of insulation, and a membrane that’s seen better days. The scan flagged a couple hot spots, but when we pulled back the insulation, the water had actually traveled sideways a good six feet from where the scan said it was wet. Like, moisture’s got a mind of its own sometimes.
We ended up doing a flood test with some dye, and that told a way different story. It was a pain to set up, and yeah, the building manager wasn’t thrilled about the idea of water on the roof, but it definitely showed us where things were really going wrong. I get why people stick to scans—they’re quick and you don’t have to haul around hoses or smoke machines—but for older roofs or anything with a green system, I’d say mixing methods is worth the hassle. Otherwise, you’re just guessing and hoping for the best... which never seems to work out in roofing.
- Gotta admit, I’m still a sucker for thermal scans—when they work, they’re like magic. But yeah, older roofs with Frankenstein layers? Total wild card.
- Flood tests are solid, but I’ve seen more than one manager nearly have a panic attack watching water on their “leak-proof” roof.
- Sometimes I’ll just go old-school and poke around with a moisture meter. Not as flashy, but less drama.
- Guess I’m saying, sometimes “quick and dirty” wins the day... at least until you hit one of those sideways leaks.
That bit about managers freaking during flood tests made me laugh—seen it happen, too.
Ever had one of those meters give you a false positive? I swear, sometimes mine just hates insulation...“Sometimes I’ll just go old-school and poke around with a moisture meter.”
Moisture meters can be a real mixed bag, honestly. I’ve had them light up like a Christmas tree on a spot that’s bone dry, then totally miss a spot where you could wring water out of the insulation. Some of it comes down to the type—pin vs. pinless, and then what kind of insulation you’re poking into. Polyiso especially seems to throw mine off, and don’t even get me started on wet vs. dry wood under a membrane.
I get why people trust the tech, but sometimes you just gotta go by feel and experience. I’ve seen managers panic over a “wet” reading only to cut open the roof and find everything’s fine. Other times, the meter’s dead-on and you’re glad you checked. It’s kind of a running joke for us—“trust but verify,” right? I always double-check with another tool or even just pull back some material if I’m not sure.
Funny thing, I had one job last winter where the meter kept going nuts near the parapet. Spent half an hour chasing phantom leaks before realizing the cold air from outside was messing with the readings. Ended up using an old-school probe and my own eyes to figure out it was just condensation, not an actual leak.
Anyway, don’t let it get to you if your meter’s acting up. They’re useful but not gospel. Sometimes you just have to trust your gut—and maybe your nose, too, if there’s that musty smell creeping in...
Sometimes you just have to trust your gut—and maybe your nose, too, if there’s that musty smell creeping in...
Totally get this. I’ve had meters tell me a section was soaked, but it was just cold from the HVAC duct below. Nothing beats actually pulling back a corner and seeing what’s up. Tech’s great, but it’s not magic.
