Moisture Meters: Take the Guesswork out of Drying

Moisture Meters: Take the Guesswork out of Drying

  • finishing
  • moisture content
  • moisture meters
  • staining

One of the most common questions that comes with selling Red Cedar decking is “how long should I wait before I stain?”. This is a tough question. Despite what a lot of people think, there isn’t a correct period of time that cedar should dry for before taking stain. There is however, a tool to determine when the time is right to slap on that first coat of finish. That tool is a moisture meter, and in this article, we’ll look at what a moisture meter does, how to use it, and where you can pick one up.

If you haven’t already, I highly suggest you read my article on Wood and Water before diving into this one

So what is a moisture meter, anyways? As the name suggests, it’s a tool we can use to determine how much water is trapped inside a material, as a percentage of the material’s dry weight. There are two types of moisture meter, and they both work off a similar concept. The first, and most common, has two pins that get stuck into the material. The device contains a battery, and when the pins are in the material it attempts to create a circuit. By measuring the resistance in that circuit, provided by the material, the meter determines the moisture content. The limitations of these meters is obvious, as it does leave a small imprint in the board, and they can only measure a single point at a time. The other type of moisture meter is what’s known as a capacitance, or pin-less meter. Capacitance meters are a bit more complex, but they work of a similar idea. The meter arcs an electromagnetic field through the material, and bases its measurement off properties of that field. The advantage of capacitance meters is that they don’t leave any marks in the material, and they can quickly and easily take measurements from the whole length of a board.

moisture meter 2

High-end pin-less meter (top),  resistance moisture meter (bottom).

moisture meter

A moisture meter can be extremely valuable when finishing your deck, siding or any other outdoor structure. We want to use a moisture meter to ensure we’re within the moisture content guidelines for the stain that we’re using. The vast majority of stain failures are caused by poor preparation, and checking the moisture content is a huge part of that. So how do you do that? It’s easy. First of all, you should check to make sure your moisture meter is adjustable for different species. If it has a specific Red Cedar setting, use that. If it doesn’t, look for a softwood setting or better yet a density setting. The density of Western Red Cedar is about 380 kg/m³ or 23 lb/ft³. For a 2-pin meter, insert the pins roughly a third of the thickness of the board deep. Keep the pins running parallel to the grain, and do this for every quarter of the board, i.e. on a 12’ board you would measure at 3’, 6’ and 9’. For a pin-less meter, simply slide the meter the full length of the board. If the majority of the board is within the moisture guidelines set out by the stain, you’re good to go.

So where can you get a moisture meter? Unfortunately, at this time we do not sell any, but Home Depot has a great selection. I recommend the General Tools Moisture Meter for a two-pin meter, or the Ryobi Pinless Meter. These can both be found at Home Depot for between $50 and $60. For a higher end model, the Extech Pinless Moisture Meter is another great model, though it’s $200.

With the right knowledge and a little extra time, you can avoid the headache of having to strip a peeling deck two weeks after its first stain. By using a moisture meter, you can take the guess work out of staining, and ensure your stain lasts as long as possible.