Understanding External Timber Cladding

What merchants need to know

Timber cladding has become a popular choice for both residential and commercial projects, making it essential that merchants are equipped to guide customers toward the most suitable options. While often selected for its visual appeal, timber cladding also serves a vital role as a rainscreen, helping shield building from the often harsh and wet British climate. However, if not installed to the appropriate standards it can lead to performance issues, including inadequate drainage and ventilation.

To ensure longevity, timber cladding should always be installed over a drained and ventilated cavity. This allows the timber to dry effectively, maintaining its integrity over time. Proper airflow must be maintained at both the top and bottom of the installation, while the supporting battens should form a consistent drainage plane.

Behind these battens sits a waterproof breather membrane. This crucial component acts as a barrier, separating the moisture-heavy external environment from the dry interior of the structure. Selecting the right fixings is equally important, to prevent staining or even compromising the cladding’s structural attachment.

Timber is a natural material that reacts to humidity by expanding and contracting across the grain. This movement is manageable as long as the building design accounts for it. British Standard BS8605 Part 1 offers useful guidance on choosing the correct board widths and thicknesses to accommodate timber movement in exterior applications.

Durability Considerations

External cladding needs to be significantly more durable than interior woodwork due to its constant exposure to moisture and changing weather. A wide range of hardwoods and selected softwoods provide natural durability, with a variety of textures and tones available to suit different design aesthetics. For species with lower natural durability, options are available that can enhance performance. These include factory-applied wood preservatives or the use of modified timber products that have been engineered for exterior use.

To support best practice across the industry, TDUK – working in collaboration with the Timber Decking & Cladding Association (TDCA) – has created the Timber Cladding Handbook, a valuable resource available at www.timberdevelopment.uk. The TDCA is also on hand to offer guidance throughout the supply chain, ensuring everyone from suppliers to installers is well-informed.