Fig 1 Traditional verandah

Design for Durability - Shielding

Timber exposed on the outside of a building can be protected by any means that reduces extremes of sunlight, temperature, wind and moisture, and encourages regular ventilation. These include natural vegetation and physical shields such as a roof or flashing.

Vegetation, such as trees and shrubs, can protect the timber as it reduces the exposure to sun, wind and driving rain. However, care should be taken to ensure that sufficient ventilation is available between the vegetation and the structure. Insufficient ventilation can lead to an excessive build up of moisture and cause the timber to decay.

Physical shielding systems include:

• Overhangs and verandahs
• Pergolas, screens and fences
• Capping and flashing
• Fascias and barges

Care should be taken in the design of all these systems to ensure that:

• Moisture is not trapped against the timber by flashing or finishes
• Leakages do not channel moisture into joints or enclosed parts of the structure.

Reference: Timber Datafile P4 – Timber – Design for Durability of the NAFI Timber Manual.

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Timber Research Unit
Department of Architecture
University of Tasmania