How and Why We Measure the Moisture in Wood

Wood, a natural and versatile material, has the unique ability to absorb and release water, striving to maintain balance with the relative humidity of the air. This dynamic relationship with moisture significantly influences the quality and usability of the wood, making it crucial to measure and control its moisture content. But why is this so important?

The Importance of Measuring Moisture Content in Wood

Knowing the moisture content of wood is essential because it affects the wood's stability and integrity. Wood that is not properly dried can contract, expand, and crack, leading to structural issues and a compromised final product. Moreover, the moisture level impacts the wood’s density and strength, which are critical factors for ensuring a high-quality raw material.

What is Moisture Content in Wood?

Moisture content in wood is the amount of water present, expressed as a percentage of the wood's dry weight. This percentage can vary widely based on the wood species, its origin, and the environmental conditions it has encountered.

Effects of Moisture Changes

• Contraction: Wood contracts and decreases in size as it dries. When moisture content drops to around 28%, the wood's internal structure adjusts, filling voids left by evaporating water molecules.
• Expansion: Conversely, wood expands when it absorbs moisture from the environment. This swelling can lead to deformations, and in some cases, can attract fungi or pests.

Different States of Wood Moisture Content

• Green Wood: Recently cut wood with a high moisture percentage, often exceeding 30%.
• Dry Wood: Wood that has been dried naturally or through artificial processes to achieve a moisture content typically between 6% and 20%. At Las Catalinas, we require wood with a moisture content below 20% to ensure quality.

Importance of Proper Storage

Proper storage of wood is essential for maintaining its moisture content. Wood should be stored in a controlled environment to ensure it dries correctly, which is crucial for its longevity and performance in any project.

Methods for Measuring Moisture Content

• Oven Drying Method: This involves weighing a wood sample, drying it completely in an oven, and weighing it again. While highly accurate, this method requires special equipment and is not practical for on-site quality control.
• Electrical Resistance Moisture Meters: These meters determine moisture content by measuring the electrical resistance between two pins inserted into the wood. They are quick, easy to use, and provide measurements with a +/-2% accuracy. This is the preferred method for our site supervisors.

Ensuring Quality at Las Catalinas

A few weeks ago, we visited the woodshop of one of our approved builders and used a moisture meter to verify the moisture content of their wood. This quality control step ensures that we use only the highest quality materials, whether for structural purposes or decoration in our projects. As the pictures below illustrate, the wood was initially too wet and was not approved for installation on site. We required the wood to dry for an additional two weeks (longer if it rained) before remeasuring.

By diligently monitoring and controlling the moisture content in wood, we can ensure that our projects are built with materials that offer superior performance and longevity. This attention to detail underscores our commitment to quality and excellence in every aspect of our work.