Wood Species: A Distinct Society
Wood species fall into two main categories: hardwoods and softwoods. From there, it gets complicated. To install wood flooring successfully, builders need to check the wood’s moisture content (MC).
But before using a wood moisture meter, they need to set it to the correct specific gravity or species setting for the wood they’re measuring. That way, the reading reflects the moisture content of that particular species.
Wood Moisture Content Variables
The MC of green (freshly cut) wood can vary a lot. A tree’s heartwood, the inner core, often has a very different MC than its sapwood, the outer wood just under the bark. According to the USDA Forest Service Wood Handbook, coast Douglas-fir, a common softwood, averages 37% MC in the heartwood and 115% in the sapwood when green. Among hardwoods, sweetgum averages 79% in the heartwood and 137% in the sapwood. White ash, by contrast, is nearly the same in both: 46% in the heartwood and 44% in the sapwood.
A wood’s MC in use also depends on where it ends up. Wood moves toward a balance with the humidity of its surroundings, so the same species can settle at a different MC in a humid coastal home than in a dry inland one. That’s especially important for wood imported from around the world.
If you’re using wood for quality floors, you need to know the general properties of each species, because they also affect the wood’s equilibrium moisture content in the finished floor.
Moisture in Wood Cells
All wood holds some moisture in its cells. Bound water is held in the cell walls, and free water is liquid water in the cell cavities (lumens). Because different species hold different amounts of moisture, they behave differently as moisture changes. Water has a big effect on wood’s properties, which is one reason different species suit different building applications.
Moisture Content
Builders need to make sure the wood’s MC suits both the flooring application and the species. Wood reaches its equilibrium moisture content (EMC) when its MC is in balance with its surroundings. Changes in relative humidity (RH) cause the wood’s MC to change, from the forest to the newly installed floor in your home.
Free Download – Is a Pin or Pinless Moisture Meter Best For You?
To measure MC accurately, installers need to set their moisture meters to the correct species. Wagner Meters makes meters for general wood applications as well as for building inspection. With the right meter, installers and homeowners can accurately measure and monitor MC for each species. Measuring accurately matters, because reaching the right EMC is part of what keeps wood products beautiful and strong for years.
As Sales Manager for Wagner Meters, Ron has more than 35 years of experience with instrumentation and measurement systems in different industries. In previous positions, he has served as Regional Sales Manager, Product and Projects Manager, and Sales Manager for manufacturers involved in measurement instrumentation.
Last updated on October 12th, 2026
800-634-9961
