E2 Buiding Code.

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Download the E2/AS3 External Moisture infomation sheet [PDF 260 KB, 3 pages]

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Published in October 2011

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NewExternal Moisture Acceptable Solution E2/AS3 - changes 1 August 2011

This information sheet covers:

The Building Code clause for External Moisture (E2) requires that buildings must be built to resist leaks, damp or the accumulation of external moisture in concealed spaces. 

E2/AS3 is a supporting document to the Building Code clause for External Moisture. E2/AS3 is a new solution for weathertight concrete and concrete masonry construction. This solution provides one way of complying with the building Code clause for External Moisture.

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Acceptable Solution E2/AS3 is effective 1 August 2011

E2/AS3 introduced on 1 August 2011.E2/AS3 is effective now. It is included in Amendment 5 of the E2 External Moisture Compliance Document.

E2/AS3 references the new Code of Practice for Weathertight Concrete and Concrete Masonry Construction published by the Cement and Concrete Association of New Zealand, which can be downloaded free or purchased as hard copy from www.ccanz.org.nz.

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 What does the new solution cover?

E2/AS3 can be used for houses and small non-residential buildings, up to three storeys and less than 1000 m2 floor area. Outbuildings, retaining walls and basement walls are not covered.

Weathertight systems are provided for:

  • Concrete slabs-on-ground and footings
  • Concrete and concrete masonry walls
  • Concrete flat roofs and decks
  • Window and door openings
  • Junctions between walls, roofs and floors
  • Junctions between concrete and timber construction.

E2/AS3 makes compliance simpler for weathertight concrete and concrete masonry design, allowing a greater range of building materials.

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Weathertight Systems:

Slab-on-ground and footings

  • Damp proof membranes (DPM) comprising bituminous sheet or polythene can be used. DPM requirements are based on NZS 4229, section 7.


  • Three types of wall construction are covered - in situ concrete, precast concrete and concrete masonry.
  • Five weathertightness systems are covered as indicated in the table below.
  • Weathertight details for control joints, windows, doors, pipe penetrations, meter boxes, junctions with timber walls and junctions with timber roofs are provided.

Wall Weathertightness Options.

Insulation in walls and Roofs

Flat roofs and decks

  • EPDM or butyl rubber membranes or bituminous membranes can be used.
  • Acceptable EPDM and butyl rubber membranes are similar to E2/AS1.
  • Acceptable bituminous membranes are based on the Code of Practice for Torch-on Membrane Systems for Roofs and Decks – http://metalroofing.org.nz/frontend/index.cfm.
  • Weathertightness details are given for parapets, roof penetrations and door thresholds to decks.

What is an Acceptable Solution (AS)?

An Acceptable Solution details one way to comply with the relevant part of the Building Code. If you follow the solution described, your building work will meet that part of the Building Code.

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