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External timber cladding; size does matter

The Timber Decking & Cladding Association (TDCA) is an independent, not-for-profit advisory organisation – established to influence and promote good industry practice. This year, our focus is around highlighting the key information that those buying, selling and using external timber cladding should be aware of.

A specific subject is the size of cladding profiles, specifically tongue and groove (T&G) which is an interlocking system where size matters most. According to BS8605 – External Timber Cladding Part 1: Method of Specifying, for medium movement timbers such as Siberian larch, the profile width for a T&G board is restricted to a maximum of 125mm.

Further guidance on tongue dimensions and movement gaps is provided with bigger gaps and tongues being required for wider boards; at 125mm wide board the standard states a minimum movement gap (mg) of 4mm, tongue width (tw) at least 15mm and thickness (tt) at least 7.5mm.

For those looking for added assurances of quality, the TDCA operates the CladMark quality accreditation schemes which cover products, suppliers and installers. They provide audited verification of compliance with good manufacturing practices and sound installation techniques trusted by the TDCA and the wider industry.

The Timber Cladding Handbook is available as a free pdf download with a printed version available for £12 (inc p&p), go to: www.tdca.org.uk/publications