What’s the Right Moisture Content for Wood Framing?

Wood framing in construction isn’t as precise and detailed as woodworking projects are. After all, you’re not carving scrolls and fine curves into it like you would for furniture or instruments. Most of the time, you don’t even see it in a finished building.

But moisture content is still important. It can affect how the building settles—and even the air you’re breathing in it. Excess moisture can cause plenty of problems down the road.

In this post, we’ll look at everything you need to know about moisture content in framing:

• The right moisture content for wood framing
• How dry framing should be before installing drywall
• When mold begins to grow on framing

Let’s start with the big question: What are acceptable moisture levels for framing?

The right moisture content for wood framing

Because framing lumber isn’t as critical of a material as wood for other woodworking projects, you’ll be fine installing it as long as the wood has a moisture content below 19%. Once it’s at the jobsite, use a wood moisture meter to check that it has reached this number.

Nineteen percent is a threshold that, if passed, can cause dampness problems and mold growth (more on that later).

However, this might be confusing if you know that wood flooring and subfloors must be acclimated to the proper equilibrium moisture content (EMC) before installation. Why doesn’t wood framing have to reach the EMC? Here’s the difference.

The difference between framing and wood flooring

Framing and hardwood floors function in two completely different roles in a building. Framing is the skeleton—the bones—of the building. Like bones in a person, you don’t usually see the framing in the finished structure. It’s there to provide support for walls, floors, and ceilings, and that’s about all.

Wood flooring, on the other hand, is more like a person’s skin. It’s the outermost layer of the floor (and all the wood framing beneath). It serves as a smooth surface to walk on and place furniture and appliances on, but also lends aesthetic virtue to the house or building.

But because of their different functions, they have different requirements. Framing materials are slightly more exposed to the elements.

They’re tough, they’re rough, and they’re not an aesthetic element in the slightest.

This gives them quite a bit of leeway. They may shrink slightly or bow just a bit as they acclimate inside the wall, but for the most part, that isn’t a problem (that’s how houses settle).

Wood flooring, though, is different. It has a function, but it’s held to much higher standards than framing. It must be fine, smooth, without cracks or—heaven forbid!—bowing or cupping. You don’t want to get a splinter walking in your house, nor do you want unsightly unevenness in your floors. You also don’t want gaps between the floorboards where they shrank!

This is why framing only needs to be below 19% moisture content, while wood flooring must be acclimated to the environment’s EMC before being installed. They serve different purposes and, as such, have different requirements.

But back to framing lumber. Does it need to have a different moisture content when you’re ready to install drywall over top? That’s up next.

How dry framing should be before installing drywall

Some framers intentionally work with wetter wood because it’s easier to nail in place. Also, wood that hasn’t been kiln dried is much cheaper—a big incentive for people to purchase it. However, they often pay a very heavy price in the long term. Excess moisture can cause shrinkage and cracking in the wood later.

Then, because the wood changes dimensions, the builders have to fix the new problems created. Wood that’s too wet can also cause mold growth, leading to other harmful problems, both for the builder and the occupants.

This is why the moisture content is important both before installation and after—when you’re ready to put drywall over top.

If the wood has too much moisture, the moisture will become trapped and cause many problems down the road.

So, whether the wood is being used inside or outside, the moisture content should be 19% or lower. This number is a general ballpark, but some wood may need some drying time before it can get to those numbers.

As we talked about earlier, mold has the potential to grow if the wood is not at the proper moisture content. Let’s explore that more.

When mold begins to grow on framing

Mold will start to grow on framing right around the 19% moisture content mark.¹At that point, the wood is holding too much moisture and can cause humid, damp conditions. If these conditions are prolonged, and the wood has not been given a chance to dry to 19%, mold spores will form.

These mold spores could spread to the interior of the building. Not only does that present the possibility of mold growth inside, but it could cause respiratory issues for the people in the building.

If the moisture issue is severe enough, it could also cause the drywall to become too wet and begin to crumble as well. You certainly don’t want that happening in a brand-new building.

Protect your structure

Framing is the skeleton of a building. If the framing isn’t functioning properly, the whole building could suffer.

That’s why it’s so important to check that the moisture content of the wood is 19% or lower before nailing it together as a frame.

Want to know more about moisture in the building process?

1. “Don’t Drywall Until You Know the Framing Moisture Content,” Först Consulting Group, LLC, August 5, 2022. (↑)