You can pick the finest timber and still watch it fail if the moisture isn't right. Timber behaves like a living thing, it breathes, expands, and contracts with the air around it. Get the moisture wrong and a perfect roofline warps, a neat floor gaps, and once-solid joints start to creak.

Every cut, joist, and board carries a memory of where it was stored and how it dried, and that memory shows up fast once the wood becomes part of a building. For builders and DIYers, understanding moisture isn't optional, it's the difference between a job that lasts and a job that disappoints.

BUCO stocks moisture-controlled, SABS approved timber and the tools to check and protect your wood, but first you need to know what to look for, how to test it, and how to keep moisture from turning a good build into a costly repair. Read on to learn the signs, the tests, and the practical steps that keep timber stable and structures sound.

Timber moisture content refers to the amount of water present in wood, expressed as a percentage of its dry weight. Naturally harvested timber absorbs and releases water depending on environmental conditions such as humidity and temperature. Treated or kiln-dried timber has controlled moisture levels, making it more stable during installation. In South Africa, understanding the Equilibrium Moisture Content (EMC) is critical because our diverse climates - from humid coastal regions to dry inland areas - affect how timber expands or contracts on-site.

The amount of moisture in timber can impact construction in several ways. Structurally, wood that is too wet may have reduced load-bearing strength, putting the integrity of roofs, floors, and framing at risk. Dimensional stability is another concern; timber shrinks as it dries and swells in high humidity, which can cause misaligned walls, uneven floors, or warped doors. Over time, high moisture can also lead to decay, mould growth, and insect infestation, which further compromise long-term durability. Ensuring proper moisture levels helps maintain the safety, appearance, and functionality of timber throughout its lifespan.

Incorrect timber moisture can result in significant issues that affect both aesthetics and safety. Warping, bending, or twisting of boards is common when timber dries unevenly or absorbs too much water. Cracking and splitting can appear along the grain, weakening boards and making joints unreliable. Loose fittings, misaligned panels, and uneven flooring are further consequences of poorly controlled moisture. In worst-case scenarios, untreated or improperly stored timber can develop rot, leading to costly repairs and potential structural failure.

Testing timber before installation is a crucial step to avoid moisture-related problems. The most accurate way to measure moisture content is with a timber moisture meter, which provides real-time readings that indicate whether timber is safe to use. Visual inspections are also helpful—look for signs such as damp patches, staining, mould, or mildew. Ideally, testing should occur after timber has been transported or stored at the building site and immediately before installation. Moisture levels vary depending on the intended use: indoor flooring and furniture typically require 8–12%, structural framing 12–15%, and outdoor timber may need slightly higher levels depending on treatment and exposure.

South African building standards provide guidance on acceptable timber moisture levels to ensure safe and stable construction. Kiln-dried timber is typically manufactured to strict specifications, guaranteeing consistent moisture content suitable for indoor and structural applications. Air-dried timber, while less precise, can be used in certain outdoor or non-structural projects but requires careful acclimatisation. Timber that exceeds recommended moisture limits should be rejected or reconditioned before use. BUCO supplies timber that aligns with industry and SANS standards, giving builders and DIYers confidence in the material they choose.

Proper storage and handling play a critical role in maintaining timber quality. Timber should be stored off the ground, covered, and in a well-ventilated space to reduce exposure to moisture fluctuations. Before installation, timber must be acclimatised to the site environment to prevent later shrinkage or swelling. Protective measures such as sealing, applying treatments, and using membranes or underlays further enhance durability. Following correct curing and finishing practices ensures that timber retains its strength and stability over time.

BUCO provides SABS-approved, moisture-controlled timber, giving homeowners, DIYers, and professionals peace of mind. Key benefits include:

• High-quality timber suitable for both structural and decorative use
• Expert advice in-store and online for choosing the right timber and handling methods
• Reliable stock availability and convenient delivery options

With BUCO, you know your timber will perform as expected, whether for major construction or home improvement projects.

For indoor use, 8–12% is recommended. Structural applications such as framing and trusses generally require 12–15%, while outdoor timber may vary depending on treatment.

Using a timber moisture meter gives accurate readings, but visual inspections for dampness, mould, or staining are also important.

Yes. Excess moisture can weaken timber, leading to warping, cracking, rot, and compromised structural performance.

Moisture meters and hygrometers provide the most reliable results, while moisture-sensitive indicators can be used for quick checks.

Kiln-dried or treated timber is engineered to maintain consistent moisture, ensuring safer installation and long-term stability.