COP v3.0:external-moisture; acceptable-solution-nzbc-e2as1

6.2 Acceptable Solution NZBC E2/AS1 


This Acceptable Solution covers the weathertightness of the building envelope.

Construction Included

All New Zealand buildings within the scope of NZS3604.

Construction Excluded

Outbuildings such as garages and other unlined structures are excluded from the scope of NZS 3604.

6.2.1 Compliance 

The provisions of E2/AS1 are designed to be adequate to protect lined, primarily residential structures, where water ingress can cause expensive damage to structure and contents and cause ill health to the inhabitants.

Outbuildings are outside the scope of E2/AS1, as the acceptable degree of weathertightness of outbuildings is often less than that of a dwelling. Awnings and covered ways are excluded because they are outside the building element and designed to be exposed to the weather.

“Other unlined structures” are also excluded. In many cases, a less robust criterion can be applied to unlined structures because:

  • leaks are more readily identified and can be rectified before they cause lasting damage,
  • the value or vulnerability of the contents may be less than that of a dwelling,
  • the buildings are generally better ventilated,
  • the building itself may be only sporadically populated,
  • the structure is accessible for inspection and maintenance.

Often the solutions contained in E2/AS1 are applied equally stringently across all non-residential unlined buildings. In many cases, this is an overly strict requirement and a more pragmatic approach more logical. Designers and compliance officers should consider the building’s vulnerability to damage from water ingress, allowing for factors such as accessibility for maintenance and intended end use when considering compliance requirements.