Is a Moisture Meter Worth It for Home Use?
A ceiling stain, a damp wall, a puddle behind the dishwasher. A cheap meter can tell you if it's still wet, as long as you read it the way inspectors do.
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In r/HomeInspections, a homeowner had a leak under the dishwasher. They'd pulled out the particleboard, dried the space and treated it. Now they wanted to know whether it was actually dry under there, and the reviews on Amazon had only confused them.
If you've got a stain on the ceiling, a wall that smells damp or a puddle that came from behind an appliance, you're asking the same question. Is it wet in there, and how do you tell without opening it up?
A cheap moisture meter is the answer, and the people who use one for a living say it works. They're just as firm that it only works if you read it their way.
What does a moisture meter actually measure?
There are two kinds, and they suit different jobs. A pin meter has a pair of short metal pins at the top. They push into wood or drywall and read the electrical resistance between them, which is why one reply in r/HomeInspections calls it a conductivity meter. You get a reading at exactly the spot the pins went in, which is what you want on wood or a subfloor like the dishwasher homeowner's.
A pinless meter has a flat pad on the back instead. You hold it against the surface and it reads through, leaving no holes, which one r/Mold reply calls a good way not to damage surfaces such as wallpaper. On the General Tools pinless meter that comes up at the cheap end, the maker puts that depth at about three quarters of an inch. That's the kind for a stain on drywall or a damp wall.
Combination meters do both, with a pad in the body and pins on top or on a probe. Either way the display shows a percentage, and the pros say to ignore it on its own.
They are designed to measure relative moisture levels, not absolute levels. You must establish what the dry areas measure (inside, partition walls in known dry areas) and then measure similar materials where you believe there may be moisture.
u/FlowLogical7279, in r/HomeInspections
The reply with the conductivity line says the rest in a sentence: a moisture meter is "a comparison device, not a measurement tool".
What should a moisture meter read?
There isn't a number. Nobody quoted here gives one, and the ones who use the cheap meters say the reading on its own tells you nothing. The General pinless will beep above a level the maker set, and the same maker's spec sheet calls its drywall readings relative. What the pros do instead is a comparison, and it's the same with pins or a pad.
- Find a dry baseline first. Hold the meter against the same material somewhere you know is dry. The commenter above suggests an inside partition wall in a part of the house with no damp. Whatever the display says there is your zero.
- Then measure the suspect spot. Same material, same setting, the pad flat against the wall. What matters is how far this reading sits above the baseline, not the figure itself.
- Keep it off tile, masonry and concrete. The same commenter says flatly not to use them on those. Asked elsewhere about a cheap meter for a house, the answer was "Wood, drywall, yes. Masonry, no." The General pinless does have a masonry setting. Nobody in these threads vouches for a cheap meter on masonry, so we'd leave that setting alone.
Can a moisture meter be wrong?
Yes, in a few ways that come up in the threads and in the two published tests.
The pinless pad is argued about inside the trade. One reply told the homeowner pinless meters aren't reliable. The one published test disagrees, for a damp wall at least. Reuben Saltzman of Structure Tech Home Inspections tested a cheap combination meter, the Extech MO55, against his Protimeter Surveymaster. Its pad agreed with the Surveymaster on a wet towel behind half-inch drywall, found without a hole in it.
Pins have their own problems. Saltzman found the same meter's cone-shaped pins "don't stick into stuff", and he had to keep it pushed into the wood to get a steady reading. A pad doesn't have that problem.
Bob Vila's testers found a different version of the same thing on the Extech. In pin mode they kept pressing the materials button, which gave them "a reading of our index fingers" instead of the wood. The meter reads whatever it's touching.
Deeper water is harder to see. Saltzman's reservation about the cheap meter was wet sheathing behind vinyl siding. Both meters registered the high moisture there. The difference was how they said so. His pro meter sounded an alarm and lit a row of lights, and the cheap one only showed a number on its display, which was easy to miss.
For a stain on drywall that's not your problem. For a wall you can only reach from the outside, it might be. The General pinless has lights and an alarm of its own, per the maker, and we found no test of it on a wall like that.
A pad only reads so deep. The maker's three quarters of an inch is the limit for the General, and water further in than that isn't being read at all. A pad also reads differently on wood, drywall and masonry, per the maker's own ranges, which is why the baseline has to be the same material on the same setting.
What moisture meter do home inspectors use?
Mostly the expensive ones. The Protimeter Surveymaster and the Tramex Moisture Encounter come up again and again. One inspector carries both and reckons the money is worth spending, because water damage is among the most expensive defects they find.
Another, asked for a homeowner's pick, named a Tramex and then said not to buy one unless you'll use it professionally.
The cheap end gets shorter, quieter endorsements. In the "Best tools" thread, an inspector recommends a General Tools meter as a good one for not much money, without saying which one. Over in r/Mold, someone named the pinless General as "as basic and reliable as it gets", and added that they're biased, because it was one of their first. That's the whole of the testimony for it: two voices, one of them naming no model.
An environmental hygienist in that thread carries a cheap Klein pinless and a cheap General combination meter, pins and pad, a different model from the pinless one above. They check any wet spot with both. Is the Protimeter more accurate? Yes, in their view, but not by enough to justify what it costs.
One combination meter in these threads comes with an owner. In the same r/Mold thread, a commenter uses the Extech MO290 for work and found it "very comparable" to the Tramex their company uses. Per the maker, it has the pad built in, a pin probe in the box and a built-in infrared thermometer as well. It sits at the expensive end, with the inspectors' meters, and that one owner is the whole of the testimony for it.
The cheap meter with a published record is discontinued. Saltzman's test put the Extech MO55's pin readings "close enough" to the Surveymaster's, on top of the wet-towel result above.
It won't replace my Surveymaster, but it would make a nice backup.
Reuben Saltzman, Structure Tech Home Inspections
Bob Vila's tested roundup named the same Extech "Best Combination", with a note that the material button is sensitive. Extech has since discontinued it, and we found no published test of its replacement.
What those two tests show is that a cheap meter can agree with a pro one on wood, and on a damp wall. They aren't a test of the General pinless. Nobody has published one that we could find.
Should you buy one?
For a stain you can't read by looking, yes, at the cheap end, and only if you use it the inspectors' way. The General Tools pinless meter costs a fraction of the pro ones and leaves no holes, and its limits are known: wood and drywall, three quarters of an inch deep, read against a dry wall.
If you also want pins for a subfloor and will pay what the inspectors pay, the Extech MO290 is the one combination meter here that someone uses for work. The method is the same with either, and it costs nothing.
Start on a dry wall. Pick an inside wall of the same material that you know is dry, and write down what the meter says there. Then go to the stain, pad flat the same way, and compare. If it reads like the dry wall, you're looking at an old mark. If it reads well above it, you've found what to point at when you call someone.