Wood Species: Same Difference in Moisture Content
Every flooring professional knows that wood isn’t just wood. From density and grain pattern to moisture retention and shrinkage, every wood species behaves differently. That’s why understanding moisture content (MC) is essential to preventing costly flooring failures.
The relationship between wood moisture content and ambient conditions is a delicate balance. Get it right, and your flooring stays stable, durable, and beautiful. Get it wrong, and you could be dealing with cupping, buckling, gapping, or warping, all of which lead to expensive repairs and unhappy clients.
In this article, we’ll cover:
- Why different wood species hold moisture differently
- How environmental factors affect moisture levels in wood flooring
- The importance of measuring MC on the job site
- How to choose the right moisture meter for different wood species
A Primer in Wood Moisture Content
All wood contains some moisture. Bound water is held in the cell walls, and free water is liquid water in the cell cavities (lumens). Even after a tree is cut down, these cells have the capacity to release and absorb moisture in relation to the relative humidity of the air around them.
Think of drinking straws packed together. No matter how tightly they’re packed, water can still move in and out of each straw. This capacity is what makes wood a hygroscopic material.
Densely packed cells (typically a characteristic of hardwood and some exotic varieties) may have a reduced capacity for free water because the inside of each “straw” is smaller, but that capacity still exists and is related to each wood’s capacity for swelling or shrinkage along with other characteristics.
In the wood flooring and construction industries, we talk about each species’ specific gravity (SG), a measure of the wood’s density: its oven-dry weight compared with the weight of an equal volume of water, based on the wood’s volume at a stated MC.
Moisture Content and Location
Since wood is a product of its environment, where a tree grows affects its wood. In the United States, wood production is often grouped into three broad regions: Western, Northern and Appalachian, and Southern.
Each region may have a predominant wood species or may produce similar species that vary from region to region based on average rainfall, the length of the growing season, or even the soil composition.
The distinct traits of different wood species are multiplied for wood which is imported from around the world. Each species is a biological structure containing different chemistry and cell types.
Even within the same region, the MC of green wood can vary a lot. A tree’s heartwood, its 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, coastal Douglas-fir, a common softwood, averages 37% MC in its green heartwood and a whopping 115% in its sapwood.
On the hardwood side, sweetgum averages 137% MC in its sapwood and 79% in its heartwood. By contrast, white ash has almost identical green MCs in its heartwood (46%) and sapwood (44%).
These variations are why lumber mills invest heavily in drying green lumber to a standard MC before it’s made into flooring or other wood products.
That’s all great in theory, but what difference does it make when you’re installing a wood floor?
Accounting for differences in region, climate, and species can make or break a flooring job. As more species are used for flooring, it takes more knowledge of these MC differences to make sure each floor lives up to its potential.
For any flooring professional, this basic fact stands: The relationship between wood’s MC and the relative humidity of its environment is highly interactive. It can be a hard lesson if you forget that, but it’s smooth sailing once you’ve mastered it.
Moisture Content on the Job Site
Changes in ambient relative humidity cause fluctuations in any wood’s MC, from the forest floor to the newly-installed wood floor on the job site. No matter the species, if the fluctuations are too great, your floor will suffer:
- Crowning
- Cupping
- Buckling
- Gaps and more
Wood of any species reaches its equilibrium moisture content (EMC) when it’s in balance with the surrounding air and stops gaining or losing moisture.
That’s why it’s so important to let the flooring acclimate on site before installation, especially when it’s moved from one climate or environment to another, even if that’s just from a local storage facility to the job site.
Free Download – Is a Pin or Pinless Moisture Meter Best For You?
It’s also why an accurate wood moisture meter is an essential tool for installing any species of flooring. Because each species will react slightly differently, having the settings right on your wood moisture meter is critical.
The same is true of engineered flooring and bamboo flooring, which can need very different SG settings from one manufacturer to another.
The Bottom Line
If your wood moisture meter has a limited range of species settings or correction tables, measuring MC accurately becomes a costly gamble. You need the right settings for each species to measure its MC precisely.
A pinless wood moisture meter like the Wagner Meters Orion® 930 has settings for a wide range of specific gravities, so you can measure many species accurately without marring finished surfaces.
When working with any species of wood flooring, the principles of moisture measurement remain the same. Be sure your moisture meter will provide the information you need because only then can you accurately measure and monitor the wood’s MC readings for each distinct wood species, and be sure your customers’ floors will provide the long-lasting beauty and strength they expect.
Learn how long it takes to acclimate wood flooring in our guide.
Tony Morgan is a senior technician for Wagner Meters, where he serves on a team for product testing, development, and also customer service and training for moisture measurement products. Along with 19 years field experience for a number of electronics companies, Tony holds a B.A. in Management and his AAS in Electronics Technology.
Last updated on October 9th, 2026
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