Wood moisture
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Wood moisture | What is wood moisture?Wood behaves hygroscopically, i.e. it absorbs water from the surrounding air and releases it again. The water content in wood is referred to as wood moisture and is expressed as a percentage of the dry weight. This value has a considerable influence on the usability, durability and workability of wood.
Methods for Measuring Wood MoistureThere are two common methods for determining wood moisture: Oven-dry method (drying in an oven): This method is considered the reference procedure for accurately determining wood moisture. A wood sample is first weighed and then dried in an oven at a constant temperature of approximately 103°C until the weight no longer decreases. The moisture content is calculated from the difference between the initial weight and the dry weight. While this method is highly accurate, it requires more time and may destroy the tested material. Electrical devices: These devices offer a quick and non-destructive way to measure wood moisture. There are two main types:
Different Types of Moisture in WoodWater exists in wood in different forms:
Impact of Wood Moisture on the MaterialExcess moistureA high moisture content (above 20-25%) can lead to several issues: Fungal infestation and rot: Wood becomes vulnerable to wood-destroying fungi that require a minimum moisture level to develop. These fungi can decompose the wood and compromise its structural stability. Deformation: Wood swells when it absorbs moisture, leading to uncontrolled deformation, especially when moisture distribution is uneven. Reduced mechanical strength: Excess moisture decreases the strength and stiffness of the wood, which can affect its load-bearing capacity.
Too little moistureExcessive drying of wood (below 6-8%) can also be problematic: Cracking: As the cell walls shrink due to moisture loss, tensions arise that can cause the wood to crack. This is especially significant in large wooden components. Increased brittleness: Very dry wood loses elasticity and becomes brittle, reducing its resistance to mechanical stress. Difficult processing: Dry wood tends to splinter when worked, and surface treatments like varnishes or paints may be absorbed unevenly.
Impact of Moisture on Wooden StructuresDimensional stabilityWood components that absorb or release moisture change their dimensions, which can cause issues with fitting, such as with doors, windows, or flooring.
Durability of wooden structuresThe lifespan of wooden constructions depends heavily on proper moisture control. Moisture-related damage, such as rot, mold growth, or pest infestation, can significantly impair the structure of a building.
Controlling Wood MoistureMonitoring moistureContinuous monitoring of wood moisture is a crucial part of quality assurance in timber construction. Modern electronic devices allow for quick and easy moisture checks before and during processing as well as in the finished structure.
Regulating moistureDrying: Wood is dried and stabilized in special drying chambers to reach the desired moisture content and minimize future moisture changes. Constructive wood protection: Using measures such as sufficient roof overhangs, ventilated facades, and water-repellent materials helps protect the wood from moisture over the long term. Surface treatments: Coatings, stains, or impregnations help reduce water penetration into the wood and control moisture absorption.
Wood Moisture Explained SimplyWood behaves somewhat like a sponge: it can absorb and release water from the air. This property of wood, to store and release water, affects how it behaves, how it can be processed, and how long it lasts. A high moisture content can cause wood to rot, warp, or even weaken structurally. Conversely, too low a moisture content can make the wood brittle, cause cracks, and make it harder to work with. To measure wood moisture, special devices or the drying method can be used. These methods help determine the exact moisture content in the wood and provide the ability to regulate it to ensure the stability and longevity of the wood. Understanding and controlling wood moisture is therefore essential for the successful use of wood in construction projects and the manufacturing of wood products.
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