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 contributes to aesthetics, comfort and structural performance. The design requirements for timber clad buildings are generally the same regardless of the actual cladding material used.
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.
Care must be taken with details at corners and where cladding meets doors, windows and other walls. 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 performs best when it is sheltered by wide eaves.
Timber cladding on walls should finish at least 150 mm above ground level. If it extends below this level, moisture uptake may occur and eventually cause deterioration of the cladding near the ground.
Where timber cladding comes close to the ground (but not closer than 150 mm), adjacent earth or pavement should be sloped away from the wall. Prior to installation, the bottom edge of the cladding should be cut to slope inwards and upwards from the outer face at an angle of 15 degrees to horizontal, so that water will be readily shed from the cladding Refer Figure 1.
Cladding of exposed non-vertical walls with timber requires that special consideration be given to detailing. Weathering may be accelerated and additional protection may be necessary, 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.
Reference: NAFI timber manual - Timber Datafile FP1 - Timber External Cladding
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