Direct fixed cladding capillary breaks are required

Issue 51 – July 2013

A cladding system is defined by E2/AS1 as: 'The outside or exterior weather-resistant surface of a building; including roof cladding and roof underlays, wall cladding and wall underlays, and cavity components, rooflights, windows, doors and all penetrations, flashings, seals, joints, and junctions'.

E2/AS1 clause 9.1.3.3 states: 'At concrete slab level, the base of the cladding system shall be as shown in Table 18, and: ... c) Be offset horizontally by a minimum of 6 mm for direct fixed claddings to prevent capillary action'.

For direct-fixed cladding installations where a suspended timber-framed floor is specified, E2/AS1 clause 9.1.3.5 states: 'At ground floor level, the base of the cladding system shall: b) For walls with direct fixed claddings, be offset horizontally from a concrete foundation wall by a minimum of 6 mm'.

E2/AS1 gives no base of wall cladding details that show how the offset detailed above is to be achieved and prevent water being drawn up between the back of the cladding and the foundation. NZS 3604 Timber-framed buildings Figure 7.11 (A) shows the bottom plate projected 6 mm past the edge of the slab to provide this capillary gap.

Summarised from BRANZ Guideline, June 2013.

Published in building.

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