"Ended up using painter's tape around the stain edges to track if it grew after the next rain."
That's a clever trick, actually. I had a similar headache last spring—couldn't tell if a ceiling stain was old or still active. Moisture meter gave me mixed signals too. Eventually, I penciled a faint outline around the stain and snapped a quick photo on my phone. After the next heavy rain, sure enough, the stain had crept past my pencil marks. Low-tech wins again...sometimes simpler really is better.
Painter's tape is smart, but I usually just snap a quick pic on my phone and eyeball it later. Had a leak last winter that drove me nuts—thought it was old until I noticed it darkening after a storm. Moisture meters can be tricky, especially if the drywall's thick or there's insulation behind it. Sometimes just waiting for the next rain is the only way to be sure...
Have you checked if there's any staining on the insulation itself? Sometimes drywall hides what's really going on behind it. I've seen leaks that looked ancient from the outside but were still damp inside the wall cavity. And speaking of moisture meters, have you tried different depths or angles? They're finicky, sure, but sometimes a slightly different approach helps pinpoint the issue better. Also curious—do you notice any patterns with wind direction or intensity during storms? Could help narrow things down...
I've been dealing with something similar lately, and honestly, moisture meters drive me a bit nuts too. They're helpful, but sometimes I feel like I'm just guessing at angles and depths until I get a reading that makes sense. I agree drywall can hide a lot, but insulation staining has been pretty reliable for me. If the insulation itself looks dark or discolored, that's usually a sign of ongoing moisture rather than an old, dried-out leak.
As for wind direction, I was skeptical at first, but it turned out to be a big clue in my case. I noticed water intrusion only happened when storms hit from a certain direction—something about how the rain was blowing against the siding. It wasn't obvious at first, but after a few storms, the pattern became clear. Might be worth keeping an eye on that next time it rains heavily.
One other thing I've found helpful is marking the edges of stains lightly with pencil or painter's tape. Then you can see if they're growing or changing shape over time. Sounds basic, but it helped me figure out if I was dealing with something active or just old damage.
Anyway, good luck—these leaks can be frustrating as heck to track down.
Have you checked if the insulation discoloration might just be dirt or dust accumulation instead of moisture? I've seen insulation look pretty nasty without any active leaks. Might wanna confirm before assuming it's ongoing moisture.
