- I’ve used a moisture meter a lot since we had a small leak by our bathroom vent a couple years back. What I do:
• Check “normal” readings in dry spots for a baseline.
• If I get anything 15%+ (on wood), I start to pay attention. Above 20% and I pull back insulation to see what’s happening.
• I always compare a few spots—sometimes insulation holds onto moisture longer, but the wood underneath is fine.
Not an exact science, but if numbers spike in one area after rain, that’s usually my cue to look closer. Funny enough, sometimes it’s just condensation from bad venting, not a leak at all… roofs keep you guessing.
Not an exact science, but if numbers spike in one area after rain, that’s usually my cue to look closer. Funny enough, sometimes it’s just condensation from bad venting, not a leak at all… roofs keep you guessing.
That’s spot on—condensation is sneaky and gets misdiagnosed as leaks way more than people realize. I’ve seen attic sheathing with 18-22% moisture after a cold snap, but it dropped back to normal once temps evened out and folks fixed their bath fan venting.
- I usually check both wood and insulation, like you mentioned. Sometimes the insulation reads high but the joists are dry—false alarm.
- Thermal cameras can help too, especially after a rainstorm. They show cold spots where water might be pooling.
- Curious: do you ever check the nails or screws for rust? I’ve found that rusty fasteners in a “wet” area are a pretty good sign of a long-term issue versus just temporary condensation.
Have you looked into air sealing around vents? In my experience, poor air sealing causes almost as many problems as failed flashing.
Sometimes the insulation reads high but the joists are dry—false alarm.
I get what you’re saying, but I’ve actually seen the opposite a few times—dry insulation, but the wood’s got hidden pockets of moisture. Especially with older cellulose, it can dry out fast on the surface and fool you. I’m a big fan of checking behind the insulation when possible, just to be sure. And about air sealing, I agree it’s important, but I’d argue that even perfect air sealing won’t save you if your flashing’s gone rogue. Sometimes it’s just both—because why would a roof ever make it easy?
Yeah, I’ve run into that too—surface looks bone dry, but poke around and you find soggy wood underneath. Especially after a big storm, I never trust just one reading. Flashing’s the sneaky culprit more often than folks think... had a “perfect” roof on paper, but water still found its way in. Roofs love to keep us guessing.
Flashing’s always been my headache too. Doesn’t matter how new the roof is, if that stuff’s not sealed right, water finds a way in—usually right where you least expect it. I’ve had roofs that looked fine from below, but once you start poking around after a storm, you find the hidden rot. I don’t rely on just the surface either. Learned the hard way: check valleys and around chimneys every time. A quick inspection beats a big repair bill later.
