Todays designers can choose from a wide variety of timber cladding products that includes solid timber boards in a range of profiles and species, timber shingles or shakes, various types of plywood and exterior grade hardboard in plain or surface textured sheets or planks.

When choosing the type to use there are a number of points which must be considered:

• The appearance required by architectural style

• Availability and cost

• Ease of installation and maintenance

• Prevailing climate and thermal performance required for a building

• The importance of additional strength given to the structure by some types of cladding

• Local government regulations or statutory requirements

Design for Cladding

As with any building material, obtaining the best performance from timber cladding depends on good design, proper construction practice and correct installation. Cladding should be considered an integral part of the overall building design as it can contribute to aesthetics, comfort and structural adequacy.

The design requirements for timber clad buildings are generally the same regardless of the actual cladding material used. Any special design requirements are detailed in the appropriate section of this data file.

To obtain the best possible performance from timber cladding, designers should give preference to building styles where cladding is sheltered by wide eaves and verandahs. This will give weather protection to the walls and, where verandahs are used, provide extra utility and increased comfort for the occupants.

Care should be taken with details at corners, and where cladding meets doors, windows and other walls. Such details must be designed and constructed to ensure that no water leaks into the structure. Provision must be made for the fixing of adequate flashing and sarking in accordance with good building practice.

Timber cladding on walls should finish at least 150mm above ground level. If this is not done moisture uptake may occur and may eventually cause deterioration of the cladding near the ground.

If timber cladding comes close to the ground (but not closer than 150mm) adjacent earth or pavement should be sloped away from the wall. During installation the bottom edge of the cladding should be cut to slope inwards and upwards from the face at an angle of 15 so that water will be readily shed from the cladding. Refer Figure 1.

Buildings clad with timber have many natural advantages on sites subject to high winds, extreme climate, highly reactive soils, subsidence or earth tremors. Unlike masonry and other rigid materials, the natural resilience and high strength to weight ratio of timber enables it to withstand far greater stresses and movement.

Where difficult site conditions are encountered designers should consult their local Timber Advisory Service for assistance and specialised design information.

When exposed non-vertical walls are to be clad with timber, special consideration may need to be given to detailing. Weathering may be accelerated and additional protection may need to be provided, particularly on north facing walls. When individual board cladding is used, sarking is essential and board overlap should be increased to ensure adequate protection from water entering the structure.