How To Test For Moisture In Wood Before Painting or Staining
Is It Safe to Stain?
Have you ever wondered if a wood surface is dry enough to paint after a rainy couple of days? It may be dry to the touch but a wood substrate (or surface) needs to be technically dry before applying a coating ----or it will eventually fail! Don't rush to paint until you test it or give it at least 3-4 days after rainfall. In high humidity areas of the country, that time period can be even longer.
Here is the Science Behind It
Eco Star Painting uses what is called a "Moisture Meter" to make that determination. General Tools has a Pin type device that gives accurate Moisture Content Readings in seconds.
To do a moisture Test, all you do is stick the two metal probes into the wood and wait for the digital LED reading to appear. It's that simple!
For wood surfaces, it's best to apply paint when it has a moisture content of 15% WME {Wood Moisture Equivalent} or less. The General MME1E Model has two testing choices; Low or High.
How to Test For Moisture Content
The tester we use operates on a 9-volt battery.
1) Remove the top cap exposing the two metal probes and stick into the wood. Test at the low setting first. You'll find the switch at the back of the unit. If it falls between 7-15% WME you are safe. If nothing is showing, switch to the High setting and start the test over again. The high setting will show a reading of between 16-35% WME
2) We recommend testing the deck floor or whatever you are about to paint in several locations. Some areas might be wetter than others, such as in the shade or near a gutter downspout.
The tester we described above can be purchased for under $25 so it is a wise investment that will last for decades. A moisture tester also has other uses. You can also test drywall or other materials for moisture. Drywall that has been exposed to excessive moisture can be susceptible to mold growth. This particular Moisture Meter Tester isn't sensitive enough to determine levels of moisture below 7% and drywall is considered compromised at a level of 1% or less. The more expensive moisture meter testers will test for these lower levels.
