Moisture Meter really high around windows?

So I’m still kind of new. Doing a condo today and my moisture meter (the one that lays on top of the surface, not the one with probes) was ready 0 to 1% on the dry wall in the middle of the room but around the windows it was 65%+, which also set off the alarm. Once I got I decided to check my sliding glass door and windows and same thing. 65%+ but quickly falls to zero. What’s the deal?

Situation number two, same inspection. The base around the toilet has had some obvious issues that said they were addressed but it doesn’t look like it. Switching the meter from day-wall to masonry (tile floor), samples from different parts of the floor came in at 50-56%. Next to the toilet it was 90-100%.

I’m thinking the toilet needs to be addressed by a contractor and plumber but I’m second guessing the window results.

Thanks for you all’s input!

Moisture meters are tricky. Hit a piece of metal corner bead and it will shoot up to 100%. Read up on how the tool works so you can better understand anomalies.

You will also find it is nearly useless on masonry for many reasons.


For general inspection purposes, the moisture meter is best used as a “relative” tool. In other words, check around a few windows in different locations. If all of them read 65%, than you likely don’t have an issue. If you see what looks like water damage or a water stain on a ceiling, check it and the area around it relative to each other.

And I agree with Brian, never trust the common moisture meter on masonry. Your higher reading around the toilet may be tile mortar saturated with pee. You did wash it afterwards right? Lol.

What moisture meter do you have?


Some ceramic tile have heavy metals in the glazing, that will give false readings on moisture meters. Like advice given for drywall always check other parts of the wall, floor or ceiling to get a feel for what is a normal reading.


As others have said, the readings are relative and they are useless on masonry… Practice around your own home and get a good meter, not the Home Depot one. I have 2, the Tramex ME5 and the Protimeter Reach Master. The latter is great for vaulted ceilings. I probably use it the most.


Never on the corner bed. Start >< 2" inches away from the corner bead.
Do progressive grid readings in 6" increments both horizontally at first then vertically.
Use a stud finder. Measure over a stud. If the moisture meter alarms, likely metal studs which will give false positives all the time all day long.

Download the metal readings for you meter.
The dryer your drywall is, the better. Readings on a moisture reader will generally range from 5 to 40 percent. A range of 5 to 12 percent is considered optimal. A reading of up to 17% percent is generally considered moderate moisture and acceptable.

Good luck.

Watch out for nail plates and plumbing, which can set the moisture meter off.
A bit tipoff around windows is a gradient. Is it dry up high, wet below? Probably real. Uniform? Probably not unless the leak is from the floor above.

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