Why is this OKAY?, is it?

Mine is not the top of the line (GENERAL) brand Relative Humidity Sensor/Meter, but it works…! When used in a Cement Brick/Cinder Block foundation walk, it always comes out with an up-high reading. I would love/appreciate your interpretations, comments, recommendations.


Morning, Pedro.
Hope this post finds you well.

The manufactures instructions should allow you to understand how to operate the instrument and evaluate the various material moisture readings therein.

I see the meter exhibiting: WALL.
The moisture meters I use post %. You select the material.
Would it be posable for you to post the model number for the members please.


@ryoung7 is right, wrong setting. The current reading is useless, do not refer to it in report.

The wall setting is short for drywall. You should be on the masonry setting.

MMD7NP Moisture Meter Manual (inspectusa.com)


You set moisture meters to the material they evaluate, regardless of floor, wall or ceiling orientation.
As well the ambient RH come into play. Then you have to evaluate the material percentage settings.

When using the ‘wood scale’ on a pin-type moisture meter, the %MC, Moisture Content, reading can range from 5% to 40% in moisture content. Generally, the low end of this reading will fall into the 5 to 12% range, the moderate range will be 15 to 17%, and the high or saturated range will read above 17%. Scales for %MC ranges are provided in the instrument instructions and should be consulted for specific surface materials measuring ranges.

How Do Moisture Meters Work?


Metal reinforcement, nails some ceramic tile glazing will cause false readings.

1 Like

Moisture meters are typically set up for WOOD. All other readings are relative. Concrete has a high relative moisture content and a high capillary absorption rate.


Interesting you said this and I agree. I find moisture readings in masonry almost useless. For masonry, I rely on other moisture indicators.

Mine is a “MMD7NP”. It is heartbreaking not to fully understand it’s principles of operation, the “How”. As an engineer myself, I have the ‘need to know’ of the theory behind the device to better understand from my ‘tech-street knowledge’ how to make the proper interpretation of its readings.

I replaced the battery and even bought a second just alike to compare readings.

My next step is to buy some similar cement blocks at my local supply to do a ‘lab mock-up’ simulation test.

I take this meter with me to every inspection site, if there is a basement wall made of bricks, I tryout a few readings. It doesn’t seem to be conclusive. I can say all those walls are soaked in Water (98%+). I have thought of discontinuing it’s use. Most of this foundation walls seem very sturdy and have taken the ‘prof of time’ and are still standing. Do I need to make a big fuss to my clients to have them ‘further evaluate by a licensed engineering professional’? I have found that most of such licensed contractors are out to sell their internal French drain basement remediation solution no matter if there is a real need for such an investment.

These series of pics illustrate my confusion. The first one is taken on a rock slab. I set the mods to masonry and move over to the foundation wall. Up and down, left and right… reading is always very high. It may be misleading to conclude that the wall is soaked.

Any thoughts?

.Uploading: 0757BB4C-5110-4208-A56A-763266D485D1.jpeg… Uploading: F0266422-EE17-455F-BE3D-95D528A634AB.jpeg… Uploading: 4BD256AA-88B2-4376-BD45-29BAF4F37136.jpeg… Uploading: 141DA40E-2733-4ABD-ADFC-2DD1BF79AC2C.jpeg…

If I were you in checking moisture on foundation block walls, I would chuck the moisture meter and follow guidelines explained here;

1 Like

The plastic wrap is a nice trick.

1 Like

Used on concrete floors as well when recently poured along with the better testing of the situ RH method.