Pay attention to cladding ventilation and drainage

Timber cladding provides a form of weather protection – but not all wind driven rain will be deflected. Timber cladding on buildings in the UK, should be installed as a 'rainscreen'.

This means the cladding should be fitted over a drained and ventilated CAVITY, to allow air flow and moisture to escape and give it the longest possible service life.

• Ventilation provision is allowed for at the top and bottom of the cladding, while the batten layer or layers – one or two depending on the orientation of the cladding – creates a continuous drainage plane.

• A waterproof breather membrane (such as those provided by TDCA member Rothoblass) is then situated behind the support battens, which separates the external wet zone from the internal dry zone of the building.

When this guidance is not observed problems can obviously occur. The good news is that these problems are easily avoided by following good practice guidance available from the TDCA.

CAVITIES

By using a series of timber battens, a cavity between the cladding and the backing wall structure can be created.

– Whilst cavity ventilation only needs a minimum gap of 6mm, the depth will be dictated by the thickness and arrangement of the battens.

– Fit insect mesh to all openings to prevent access by small mammals and large insects into the cavity (you cannot effectively exclude very small insects).

– Metal vermin mesh is needed at the base of all cavities near the ground.

For more detailed information, you can also refer to BS 8605 External Timber Cladding Part 1 - Method of specifying, which is designed to help manufacturers and specifiers. (Contact us if you are interested in purchasing this standard as we can offer 15% discount on BSI price)