How Deep Should Pins Be Driven into Wood? (And Other Tips)

When you use a pin moisture meter, the way you insert the pins makes all the difference.

Let’s say you’re planning to make a wooden chair. And let’s say you use a pin meter to check the wood’s moisture content, but the pins aren’t pushed in very deep.

Your meter displays a reading that seems to be within acceptable levels, so you go ahead and craft the chair. Later on, you notice signs of moisture damage on your chair—shrinking in the chair legs and warping on the seat.

What happened?

Since the pins didn’t go far enough into the wood, the meter couldn’t measure the moisture hidden below that point.

Failing to measure deep enough or driving in pins incorrectly can cause you to get inaccurate moisture readings, leading to costly moisture damage and ruined woodworking projects.

So let’s break down the correct procedure for using a pin moisture meter to get accurate results—starting with how deep you need to drive the pins into your wood.

We’ll cover:

• How do pin moisture meters work?
• How deep should you drive pins into your wood?
• Bonus tips on using pin moisture meters
• Pin vs. pinless meters

Let’s first talk about how pin-style wood moisture meters work so we can better understand how to use them.

How do pin moisture meters work?

Pin moisture meters measure wood moisture content by measuring the flow of electricity between two metal pins.

Because moisture conducts electricity, wood moisture levels can be determined by how well electricity passes through a piece of wood.

When you use a pin meter, its pins must be in the wood to properly detect moisture. Once the pins are pushed in deeply and a reading is taken, electricity flows between these pins through the board. If the electric current flows easily through the wood, the board contains more moisture. If there’s more resistance, the board contains lower moisture levels.

Sounds simple enough, but incorrectly inserting the pins can lead to inaccurate moisture readings.

To properly insert moisture meter pins, you need to make sure you’re putting them in the right way, and that you’re driving them in at an appropriate depth.

How deep should you drive pins into wood?

The United States Department of Agriculture recommends driving pins down to ¼ to ⅕ of your wood’s thickness.¹

Many pins are about 5/16” long, which will suit much of the wood you work with.²

However, if you’re working with overly thick pieces of wood, you might need a different length pin to get a deeper measurement.³

Fortunately, many pin meters allow you to switch out pins or hook up pin attachments that allow you to measure at different depths.⁴

You’ll want to use shorter pins for thinner pieces of wood. Otherwise, the pins could push through the wood, accidentally measuring the materials behind it instead, which can throw off your readings.

For thicker wood, you’ll want longer pins. Shorter pins won’t measure deep enough and you might miss out on moisture pockets deep within the wood. Measuring Only near the surface won’t give you a complete picture of your wood’s moisture levels.

Without knowing the true moisture level, you could end up using wood with high moisture levels, leading to costly moisture damage in the DIY projects you worked so hard to create.

This is why it’s important to consider the thickness of your wood before deciding which length pin to use.

But depth isn’t the only thing you need to consider. You’ll also need to think about how you prep the meter and where you insert the pins.

Bonus tips on using pin moisture meters

Keep these tips in mind to help ensure more accurate readings!

When using a pin moisture meter, you’ll want to:

• Correct for wood species: Different species of wood have different chemical compositions that can affect conductivity. So if you don’t change the species settings when measuring different types of wood, you’ll likely get inaccurate readings. Fortunately, many meters allow you to input the species before you take readings, or they’ll come with species correction guides.

• Correct for temperature: Wood temperature can also impact moisture readings if it’s quite a bit higher or lower than room temperature. You can account for this by using a temperature correction chart.

• Confirm meter calibration: If you’ve had your meter for a long, long time, or it’s suffered bumps and drops and a lot of wear and tear, it’s possible for its calibration to be off. If you have any reason to suspect your meter’s calibration is off, check it with a calibration reference tool.

• Measure in multiple areas: Pin meters can only measure in one area at a time. That’s why it’s important to measure in multiple areas across a piece of wood to ensure you’re getting the full picture of that wood’s moisture content. Otherwise, you could miss moisture pockets that could later lead to moisture damage.

• Use appropriate pressure: To drive your pins into wood takes adequate force. For harder wood, this may require you to apply even more pressure and may prove difficult. Just be careful not to push so hard that you break the pins.

• Keep extra pins on hand: Always keep extra pins with you. This way, if your current ones break you won’t have to wait until you can order new ones to finish your job.

Now that we’ve talked about the do’s, let’s cover the don’ts.

Things to avoid to prevent inaccurate readings

Depth and temperature aren’t the only things that interfere with accurate moisture readings. Wood abnormalities—even surface moisture—can all mess up your moisture measurements.

In short, you’ll want to avoid:

• Testing on wood with surface moisture: If you’re using uninsulated pins, surface moisture can interfere with the conductivity in the wood, which can result in inaccurate moisture readings. Insulated pins, however, are not affected by surface moisture, so you may want to have some on hand.

• Testing over wood abnormalities: Wood abnormalities like wood knots or unusual grain patterns interfere with the meter’s ability to take measurements, which leads to inaccurate readings. This doesn’t mean you have to measure on flat surfaces, but you’ll want to avoid measuring over substantial wood blemishes or abnormalities.

• Testing only at the ends of your boards: Naturally, the ends of the boards dry more quickly than the middle. So a test at the ends of a board could register as dry even though its center is still wet. You’ll want to take several measurements throughout the length of the wood.

Once you get your moisture reading, you’ll want to confirm whether your wood has reached the proper moisture content.

How to interpret moisture readings

Let’s say you measured everything correctly. You corrected the meter for species and temperature, and you measured in the right places. And when you finished your moisture meter displayed a high moisture reading.

Now what?

It’s time to determine whether your wood has reached the target moisture content.

The moisture level you want to reach is largely dependent on the wood’s final destination. Will the finished project be indoors or outdoors? In a humid or dry climate?

This is a crucial question to answer because wood responds to the moisture conditions of its environment.

If the air is dry, the wood will release moisture to match it. If the air is humid, the wood will absorb moisture until it matches the moisture levels in the air. The moisture level at which wood has fully adjusted, or acclimated, to its environment is called equilibrium moisture content (EMC). The wood may experience swelling or shrinkage as it goes through these changes. It will stabilize when it reaches its EMC.

For this reason, the moisture content you want your wood to reach depends on the moisture conditions of your wood’s geographic location.

In other words, your moisture content should be close to your area’s EMC. (If you’re looking for the specific EMC of your area, you can consult this page.)

Your ideal moisture content readings will also depend on whether your project will be indoors or outdoors. Typically, the inside of a house is drier than the outside.

In general, your ideal moisture levels will be:

• 6-9% for indoor projects (like wood flooring—although you’ll ultimately want to follow manufacturer guidelines)
• 9-14% for outdoor projects
• 19% max for construction projects

Once it’s reached the right moisture content, your wood is safe to use. You won’t have to worry about it warping and ruining the project you’ve put so much time and work into.

Pin vs. Pinless meters

Now you’ve got pin meter measurements down, but did you know that pin-type moisture meters aren’t your only option?

If driving multiple prongs into a hard piece of wood over and over again doesn’t sound like something you want to bother with, a pinless meter might be the right meter for you.

As the name suggests, pinless wood moisture meters don’t have pins. They only have a flat sensor pad you place against the wood to get a moisture reading. The sensor pad emits electromagnetic waves, which are used to measure the moisture content of wood.

The fact that pinless meters don’t have any pins means that you won’t have to worry about the time, money, and effort of:

• Struggling to drive pins through hardwood
• Breaking and buying replacement pins
• Damaging your wood by leaving behind pin holes.

On top of that, pinless meter readings are virtually unaffected by temperature. They also measure deeper into the wood to get more accurate measurements.

Want to learn more about pinless meters?

Head on over to “Pinless Moisture Meters: A Beginner’s Guide” to learn more about the accuracy and convenience of pinless options.