DOES YOUR EXTERNAL TIMBER CLADDING MEASURE UP?
ROOFING & CLADDING
The Timber Decking and Cladding Association offers advice on how to ensure you specify compliant timber cladding.
Enquiries received by the Timber Decking and Cladding Association (TDCA) highlight an ongoing issue: cladding profiles that don’t conform to established best practice. Getting the specification right at the design stage is critical to the performance and longevity of any external timber cladding, with board dimensions playing a major role.
One recent enquiry was seeking a 22x219mm European larch shiplap cladding – a board with a width-to-thickness ratio of 10:1. This is outside the limits set by BS8605-1:2014, which recommends ratios between 4:1 and 6:1, and limits board width to 150mm (except timbers such as Accoya, which can extend to 195mm due to its ‘very small movement’ classification). Unless designers, specifiers, and suppliers all understand and apply the correct standard, problems are likely to surface later down the line. A width-to-thickness ratio of less than 4:1 can also be used providing the increased material and installation costs (relative to wider boards) are acceptable. For standard species, exceeding those limits increases the risk of performance issues.