Thread: Moisture meter readings

Is there an acceptable level of moisture on interior drywall? My moisture meter is giving me 6% and I don't see any visible water damage. This is an exterior wall on the main level and a bedroom above it.

Originally Posted by Bill Temme

Is there an acceptable level of moisture on interior drywall? My moisture meter is giving me 6% and I don't see any visible water damage. This is an exterior wall on the main level and a bedroom above it.

Hi Bill
Without being there, I expect that 6% does not indicate a problem in that area.
What are the moisture readings on nearby walls?

I recommend you get to know your equipment and the conditions you are looking for.
Start in your own home. Take readings of interior and exterior walls at different heights above the floor and in different rooms. This will help you to set a baseline to determine just what is normal and what is not. Checking around windows is also a good place to see moisture readings.

I would say that 6% is fairly normal in an occupied home. The moisture levels of drywall are very dependent on the RH(relative humidity) in the area. I have seen drywall in a garage show 15% with a pin type meter on a hot summer day with high RH, and the high reading was due to the high humidity and nothing more.

I routinely see 8-10% in most homes here in Florida. You will need to scan many walls in many homes to understand what is typical in your area. It's more important, with low numbers, to look for anomalies that are different than surrounding areas.

Many different types and brands of meters show different results when scanning the same wall. What meter are you using?

You will never find a 0% reading on a material (like gypsum) that absorbs humidity.

Most finished basement walls I see can peg 16% -18% and I have no negative comments about it.

I think the responses covered most of the things you need but at the risk of redundancy I will attempt to add point or two.
Moisture content of drywall by itself is generally not an issue unless there are high levels or if the levels change over an area. If you are using a pin meter and get a 6 or 8 in the middle of a wall you may get a 8 or ten in some other areas lower on the wall. The process of sampling is called moisture mapping and what you are looking for is something that indicates something that should not be there....
In slab construction you will usually get higher readings lower on the walls and in most homes the interior partition walls will be lower than exterior walls.
If there is a leak it will usually peg the meter well over 20. I there are leaks from exterior moisture it will depend on the delta or difference from the middle of the wall to the areas of higher readings, usually around a window or door.

I always establish a baseline. I will go to a known "dry" wall and take readings. Here is the Pacific NW a vacate home with minimal heat can read 10-12%. Once I have a baseline then I will start looking at the suspect areas. I don't recall where I saw it but I read that home interior can be up to 15% without issues. I look for large deviations from the norm and then go from there. If your seeing 6% from most of the home and then see a wall under a window read 15% then you may have a problem. On the other hand if you consistently seeing 12% throughout the home there may be no problem.

//Rick

Let's say you got hauled into court and some wiz-bang attorney got curious about your moisture meter and asked if it was recently calibrated? "How do you know, Mr. Inspector, that the 6% reading was actually accurate?" I expect that the resulting spiral of death would be immediate.

I personally have no idea how accurate my meters are and would put little or no faith in the specific levels they were giving me. I would however find the readings useful from a relative point of view - how did this section a particular material compare to another section of the same material. If the readings are notably different and I didn't have a "comfortable" explanation for them, then I'd have a question as to what was going on and I would recommend that things be checked out. The nice thing about this approach is that you can't be proven wrong since you made no definitive statement. That's not to say that if water was running down the wall you should take a wishy-washy stance.

Originally Posted by Eric Barker

Let's say you got hauled into court and some wiz-bang attorney got curious about your moisture meter and asked if it was recently calibrated? "How do you know, Mr. Inspector, that the 6% reading was actually accurate?" I expect that the resulting spiral of death would be immediate.

... I would however find the readings useful from a relative point of view - how did this section a particular material compare to another section of the same material.

And that is the answer you give the attorney, that you are not using the moisture meter to state the precise level or moisture at any given sample point, that you are using the moisture meter to compare areas of the same material to each other.

If you were to have, and maintain, a calibrated moisture meter and you could document its calibration, the attorneys next question would be: can you show me the precise sample points you took the calibrated readings? If you had gone the calibrated moisture meter route you should also have taken photos of the room and its location (to identify 'that' room) and photos of each wall of that room with identifiable points on the walls showing the precise location sampled and the an identifier which relates to a table showing the moisture reading at that identified sample location.

Best to use it as you say: for comparative purposes for comparative moisture levels in different areas of the same or different rooms in the same material (don't switch between drywall and wood, that would throw off even the comparative readings, you could compare drywall to drywall and wood to wood in those different areas).

My MM has a "Test" feature. Touch the pins to a pad on the cap, and it should have a ?% reading.

Originally Posted by Eric Barker

Let's say you got hauled into court and some wiz-bang attorney got curious about your moisture meter and asked if it was recently calibrated? "How do you know, Mr. Inspector, that the 6% reading was actually accurate?" I expect that the resulting spiral of death would be immediate.

I personally have no idea how accurate my meters are and would put little or no faith in the specific levels they were giving me. I would however find the readings useful from a relative point of view - how did this section a particular material compare to another section of the same material. If the readings are notably different and I didn't have a "comfortable" explanation for them, then I'd have a question as to what was going on and I would recommend that things be checked out. The nice thing about this approach is that you can't be proven wrong since you made no definitive statement. That's not to say that if water was running down the wall you should take a wishy-washy stance.

Thanks. That is how I state it to everyone.. I am not trying to cover my backside by doing so but I am just being realistic with the folks. I could walk out of a factory with any moisture meter that I just watched them test and by the time I use it on my first inspection it could already be off.

Originally Posted by Rick Cantrell

My MM has a "Test" feature. Touch the pins to a pad on the cap, and it should have a ?% reading.

Should have a full scale "100%" reading - that is mainly a 'battery test', if the meter does not go full scale then the battery is too low to provide 'accurate' readings ... hopefully we will not be asked to 'define "accurate" ... '.

My understanding is the wire across the pins is a resistance test, not a battery test.

GE Protimeter

4 Battery
The Protimeter Mini BLD2000 is powered by one 6F22 9V battery. Replace it when the low
battery symbol flashes by removing the cover on the back of the instrument. Ensure correct
polarity when inserting the new battery.


5 Calibration Check-
Check the calibration of the Protimeter Mini BLD2000 in accordance with your quality
control procedures by holding the electrode needles across the exposed wires of the
Protimeter “Calcheck” device.


Correctly calibrated instruments will register a value of 17 – 19. Instruments that register a
value outside this range should be returned to GE Sensing or to an authorized GE Protimeter
distributor for servicing.

Originally Posted by Raymond Wand

My understanding is the wire across the pins is a resistance test, not a battery test.

GE Protimeter

4 Battery
The Protimeter Mini BLD2000 is powered by one 6F22 9V battery. Replace it when the low
battery symbol flashes by removing the cover on the back of the instrument. Ensure correct
polarity when inserting the new battery.


5 Calibration Check-
Check the calibration of the Protimeter Mini BLD2000 in accordance with your quality
control procedures by holding the electrode needles across the exposed wires of the
Protimeter “Calcheck” device.


Correctly calibrated instruments will register a value of 17 – 19. Instruments that register a
value outside this range should be returned to GE Sensing or to an authorized GE Protimeter
distributor for servicing.

Does it say the Calcheck device is in that pad in the cap? I thought it was a separate device, or maybe it was a separate device years ago and is now built into the cap?

Years ago the one I had you just touched to a piece of metal and the needle went full scale showing the battery was good. Times, equipment, and technology do keep changing and getting better. With yours, you could say that you did calibrate it as specified by the manufacturer and that it read within the calibration limits.

I understand there is the cap model and the wire strip type. My unit has the wire strip test, and if the battery is low its indicated on the LED read out. If the unit does not register between 17-19 +/- 1 when tested by either method (cap or wire) then the unit is defective and the manufactures states return to factory.

Originally Posted by Jerry Peck

Should have a full scale "100%" reading - that is mainly a 'battery test', if the meter does not go full scale then the battery is too low to provide 'accurate' readings ... hopefully we will not be asked to 'define "accurate" ... '.

Has the battery test and % moisture test
I'll get it out to see just what it does.

I find that by sticking the needles into my hand or finger to be the best calibration testing method. It registers 100% when the blood flows! All those that have never stuck themselves with a pin meter raise your hand!

I don't see any hands up!

Originally Posted by Scott Patterson

I find that by sticking the needles into my hand or finger to be the best calibration testing method. It registers 100% when the blood flows! All those that have never stuck themselves with a pin meter raise your hand!

I don't see any hands up!

Just to make sure it is working and registering moisture I do push it against the heal of my hand. You don't have to draw blood to get the needle to move pretty far up.

Originally Posted by Ted Menelly

Just to make sure it is working and registering moisture I do push it against the heal of my hand. You don't have to draw blood to get the needle to move pretty far up.

I could get the needle to go full scale on my pin type by pressing the pins against my hand, my sensing types would read quite high but not full scale. None of those 'tests' would indicate calibration, just that it was 'working'.

Yes that sort of test method would not hold up in court.