That flood test is one of those things that sounds like overkill until you skip it and end up with buckets all over the house... ask me how I know. I did a patch job on my garage roof last year, figured it was watertight, then a week later we got a downpour and I found out the hard way it wasn’t. Ended up spending more fixing water stains inside than I did on the actual repair.
I’m in the Midwest, so freeze/thaw is a big deal here too. I’ve noticed even after a good install, seams can start to separate after a couple winters. Has anyone tried using one of those infrared cameras to track down leaks? I keep seeing them recommended but not sure if they’re worth the money for a DIYer. Or maybe there’s some other trick for finding those sneaky leaks that only show up when it rains sideways?
- IR cameras can work, but from what I’ve seen, they’re best when there’s a temperature difference—like if it’s sunny outside after rain, or you run the AC and look for cold spots where water’s coming in. Not always foolproof, though.
- For flat roofs, I’ve used a garden hose and just worked in sections—sometimes you see a slow drip inside way after you’ve moved to a new spot, so it takes patience.
- I’ve also tried talcum powder on suspect seams; water tracks make it obvious where it’s sneaking in.
- Midwest winters are brutal on seams. I’m curious if anyone’s tried those liquid-applied membranes as a patch—do they hold up better than tape or caulk in freeze/thaw cycles?
- Tried the liquid membrane stuff last fall on a couple seams—honestly, it held up better than caulk for me, but not perfect. Still got a tiny leak after a big freeze/thaw swing, but it was way less than before.
- Tape never lasted through winter here (I’m in northern Illinois).
- Garden hose trick worked once, but sometimes the water just finds a new path... super frustrating.
- If you go with liquid membrane, make sure it’s warm enough when you apply or it peels weird. Learned that the hard way.
Flat roofs are a pain in the Midwest, no doubt. I’ve been through a few rounds of patching on my own place (Chicago burbs), and honestly, I’ve had mixed luck with liquid membranes too. One year I put it down in late October—big mistake. It looked fine at first, but after a couple of those freeze/thaw cycles, it started to bubble and peel at the seams. Next spring, I redid it when temps were steady above 55°F, and it held up way better.
Tape’s never survived a winter for me either. I tried that “super sticky” stuff that’s supposed to be good for cold climates, but by March it was flapping in the wind.
Have you ever tried infrared scanning or using a moisture meter to track down the leak? Sometimes the water travels way farther under the membrane than you’d expect. I found a leak once that started near a vent pipe but showed up 10 feet away at the wall. Makes me wonder if some of these leaks are actually from flashing or penetrations rather than the field seams themselves...
That’s a pretty common story with Midwest flat roofs, especially when it comes to timing repairs. Liquid membranes really don’t like cold weather or those wild temp swings—seen plenty of jobs fail just from being applied too late in the season. I’m with you on the tape, too. Most of those “cold climate” tapes just don’t stand up to our freeze/thaw cycles, no matter what the label says.
You’re right to suspect flashing and penetrations. In my experience, leaks almost always start there, not in the middle of the field. Moisture meters and IR scans can help, but even then, water finds crazy paths under these membranes. It’s frustrating, but you’re definitely not alone.
