How wide should the ventilation cavity be behind timber cladding?

The minimum ventilation cavity depth is 25 mm for standard applications, with 38–50 mm recommended for optimal performance. The cavity must be open at top and bottom to allow air circulation driven by the stack effect (warm air rises, drawing cool air in at the base).

The minimum ventilation cavity depth is 25 mm for standard applications, with 38–50 mm recommended for optimal performance. The cavity must be open at top and bottom to allow air circulation driven by the stack effect (warm air rises, drawing cool air in at the base). Cavity openings should be protected with insect mesh (minimum 3 mm aperture) to prevent pest ingress. For buildings above 4 storeys, cavity barriers are required at each floor level, with open-state barriers that allow ventilation but close in fire conditions.

Why this matters

This question relates to Timber Facade Design: Weathering, Maintenance & Detailing, which covers the broader topic in detail. Understanding this specific aspect helps architects, builders, and timber dealers make informed specification decisions.

For full context and additional technical detail, see our comprehensive guide:

→ Timber Facade Design: Weathering, Maintenance & Detailing

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About this answer

This answer is part of the PuurModulair Knowledge Base — comprehensive timber specification guidance for architects, builders, and dealers across the UK, EU, and Scandinavia.