How To Use A Moisture Meter On Drywall & Wood? (6 Step Guide)

#4. Select Either The Pin Or Pinless Sensor

Many of the best drywall moisture meters have to moisture sensors that you can use. The pin sensor consists of two metal pins that you can insert into softer materials such as carpet.

As a home inspector, I frequently find that the corners of basements have water problems (usually due to poor exterior grading). Well, having a pin sensor is great because I can probe the corner carpet to see how wet the floor is. A pad sensor will not give me an accurate reading.

However, if you want to test a hard or flat surface such as drywall or wood paneling, the you definitely want to use the pad (flat) sensor. You don't want do damage the wall or ceiling material.

With the flat pad sensor, you can sweep large areas very quickly checking for moisture.

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#5. Beware Of False Signals

Now it's time to actually use the moisture meter. But before you do, it's important to realize that there are some limitations and false signals with moisture meters.

Metal Corner Beads

In my experience as a home inspector, one of the most common false signals with these meters are with metal. Especially with drywall or gypsum walls, there are almost always metal strips at the corners of walls and windows where a metal "corner bead" was installed.  Sometimes instead of metal, drywall installers use vinyl corner beads, but I think it is pretty rare.

Frequently when I am checking a basement window, I am very conscious that the metal strips will cause a false reading, and the moisture meter will usually go to 100%.

If at anytime you are in a drywall corner area or within a few inches, and you get a reading of 100%, there is a good chance that it is a false signal.

Significant Moisture Readings

Besides the metal corner beads, it's also important to realize that not all moisture readings are equal. In my experience, if the moisture meter signals 5% to 10% moisture, this barely even registers to my brain.

I am always looking for more substantial readings, more like in the 60% to 90% range.

Concrete Or Masonry Block

Many moisture detectors have a "masonry" mode to detect moisture in concrete or block, but in my experience as a home inspector, I have found that it isn't reliable whatsoever.

Concrete and cinder blocks naturally "breath" and are not water tight. Moisture is constantly going in and out of concrete because it is a porous material. I have never put a moisture meter on a foundation wall and not received a very high moisture reading. If I found this significant, then I would be worried about every foundation I ever inspected. I do not take these readings seriously.

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#6. Where Can I Use A Drywall Moisture Meter?

As an inspector, the absolute most common areas I use my sheetrock moisture meter on gypsum walls, drywall ceilings, and wood paneling --- that's pretty much it.

Stains And Drywall Patches

I walk through the house with a high powered flashlight, and any time I see what looks like a moisture stain, I pull out my moisture tester and check to see if the stain is active. If the moisture meter has a reading of 20% or more than the surrounding area, then I know there is still some kind of leak (or condensation problem) going on at this spot.

In addition to moisture stains, I also always check drywall patches. There is a reason that someone did a repair, and quite often it has to do with a plumbing leak, especially if it is the ceiling.

Construction Materials

Before installing framing, wood floors, or other materials, it can be a good idea to check their moisture content especially if they have been outside or in the rain. 

You may want to wait until the material dries out and drops below a certain moisture level before the installation.

If the moisture content of wood material is excessive prior to installation, it can cause the wood to warp and bow after it has been installed.

Be careful with wood however because the readings may vary with wood species, temperature, and chemical treatments.

Basements

Home inspectors frequently find water problems in basements, it's almost a cliche. The usual reason that basements have water issues is that the exterior grading is very poor. The ground should slope away from the home, but frequently it is flat or even sloping towards the home.

Related to exterior grading, I frequently inspect homes that have missing downspout extensions or even missing elbows. The roof discharges large amounts of water during rainstorms, and if your downspouts are spewing water by the corner of the home, water can easily intrude into the basement (especially the corners).

Many times when I am doing a home inspection, even I don't suspect water issues, I still quickly take a few moisture readings of the corners and a few other areas below grade.

Behind Decks

Many times I find water problems in the basement or ground level of a home where a deck is connected.

The deck is connected to a home by using lag bolts that are screwed into a piece of wood called a ledger board.

Before the deck is connected, the contractor is supposed to install metal or plastic flashing to prevent water intruding in the home during rain storms. In my experience as a home inspector, I find that 90% are not properly flashed.

This is why I always check underneath the deck (inside the home) at the interior wall. If I am getting moisture readings inside the home under the deck, then I know that the deck is not properly flashed and is leading to water problems --- and may lead to mold problems.

Conclusion

There are many benefits of using a moisture detector as a homeowner or a professional. It can be very difficult to determine leaks in a home that aren't visible to the naked eye. 

Even though I can sometimes smell water issues in a basement --- it is very distinctive --- it is still important to confirm this suspicion and also to determine where the water is coming from.

Using a moisture meter is pretty simple, just make sure it is in the correct mode, avoid false signals, and know where to use it.

I hope you enjoyed my guide on how to use a meter. If you have a question or would like to share an experience with drywall moisture meters, then leave a comment below.