Learning how to use a wood moisture meter is more important than you may think. A lot depends on making sure the wood is below a certain moisture content before any paint or finish can be applied.
Using a moisture meter to proactively make sure wood stays below certain levels can also help prevent rot which needS high wood moisture to grow.
There are a wide variety of moisture meters and two main categories that we’ll discuss so you can make sure you are getting an accurate reading each and every time.
Pinless Moisture Meter
Pinless moisture meters sit on the surface of the wood and use an electromagnetic sensor pad to detect differences in the density of the wood caused by differing moisture content.
These are a particularly good choice if you’re looking to test fine woodwork, furniture, or wood floors that you don’t want to be poking holes into.
The pinless design means that you’ll need to calibrate the moisture meter each time you use a different species of wood or you may not get accurate readings.
TheY can usually handle moisture measurements on woods 1/4” to 3/4” thick, but they cannot detect much beyond that.
Pin-Type Moisture Meters
Pin-type moisture meters work by inserting two pins into the wood surface and then measuring the electrical resistance between the two points. Water is an excellent electrical conductor and so wetter wood means better electrical conductivity and that translates to a higher moisture reading.
Pin-type moisture meters seem to be more accurate in my experience especially when checking thicker wood like framing lumber or anything else more than 3/4” thick.
While they do mar the surface with two tiny pin holes, I find that using these in hidden areas often is the best option. The pinholes are largely invisible except on white painted surfaces.
The moisture meter I prefer to use is the General NMD4E and I find it works great for anything I may need at a very fair price.
Why Moisture Content Matters
Checking the moisture content of wood is important for a lot of reasons. Knowing where you stand can help you resolve issues and better plan your finishing schedule. Here are a few of the ways using a moisture meter can help you.
PaintIn wood with a high moisture content is a bad idea. It traps moisture inside and can lead to quick paint failure as the moisture pushes the paint right off the wood surface no matter what type of paint or finish you use.
I have been too anxious to paint at times and started priming without checking moisture content of the wood. No matter how dry the wood surface feels you shouldn’t prime or paint any wood that is more than 13-15%. Anything above that and you are asking for trouble.
Rot requires at least 35% moisture to flourish. So, keeping any wood on your house below that threshold will prevent rot from happening. That seems easy, right? It really is.
If you notice areas of the house that get constant splash back from clogged gutters or from deck surfaces you can use your moisture meter to test them and make sure they are safely below the rot zone.
If not then you can take preventative action to stop the rot before it starts by making adjustments to your landscaping, gutters, or anything else that is causing too much splashing water on your wood siding.
We’v been talking about moisture meters for wood, but many also can work in plaster or drywall and can help you find small potential leaks before they turn into big problems.
Pick up a moisture meter with functionality for masonry, drywall, or plaster and test water stains on ceilings to see if they are new leaks or previously repaired leaks. Also check other suspect areas around plumbing to help determine if there really is an active leak.
Founder & Senior Editor
I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.