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Ventilation

All fully supported metal roofs must have provision for ventilation of the timber substrate to allow dissipation of condensation.
Copper is not corroded by retained moisture, but most other metals can suffer degradation from continued exposure to moisture. Zinc is particularly prone to corrosion, but zinc coil is available with a high-build lacquer or specially treated underside to avoid the effects of retained moisture. Where the design is likely to cause continued moisture or cannot provide sufficient ventilation, enhanced underside treatments should be considered for zinc.

The best provision is always to provide sufficient ventilation at the eaves and ridge, and the minimum of a half an air change per hour to ensure that any condensation is not retained. Proprietary vents made from aluminium or polyethylene can also be used at one per 50m2. These should be placed over a purpose made hole or at the intersections of the 3mm gap between the plywood sheets. See Ventilation.

Clause: 
015_004_006_000_000_000_000_000_000
Clause Number: 
15.4.6
/cop/other-products/standing-seam-cladding#ventilation
Revision Category: 
0 - Clause Removed
Revision Detail: 

Clause removed during a comprehensive revision of Standing Seam Cladding. The subject is now discussed in Standing Seam Ventilation.

Draft Clause: 
014_004_006_000_000_000_000_000_000