Wet Areas
Designing and detailing to ensure water remains within the wet area and to deal with the effects of humidity and moisture.
Statutory requirements
The design and installation of wet areas must comply with NZBC clause E3 Internal moisture.
Its objectives are that wet areas must:
- safeguard against illness, injury and loss of amenity from the accumulation of moisture
- protect adjacent household units from water damage.
The objectives require that:
- spaces have adequate thermal resistance, ventilation and space temperature
- any overflow must be disposed of appropriately
- surfaces are impervious and easy to clean.
The compliance document E3/AS1 provides a means of meeting clause E3 Internal moisture requirements.
Currently, E3/AS1 contains minimal information, is outdated and is limited as a compliance document. Therefore means of compliance with E3 Internal moisture will generally be Alternative Solutions.
Other Building Code clauses that may be applicable to wet areas are summarised in the following table (see www.dbh.govt.nz/building-code-compliance-documents).
| Clause | VM/AS | Relevance to wet areas |
| B1 Structure | B1/AS1 | Cites NZS 42233 Part 3 Glazing in buildings as a means of sizing glazing to carry loads from wind and human impact (see also F2 Hazardous building materials). |
| B2 Durability | B2/VM1 | Cites evaluation of durability by taking into account: • in-service history • laboratory testing • performance of similar materials. |
| B2/AS1 | Specifies the durability requirements of building elements based on the difficulty to detect or access problems, or replace them. | |
| C Fire safety | C/AS1 | Part 7 D Spread of fire. |
| F2 Hazardous building materials | F2/AS1 | Cites NZS 4223 Part 3 Human impact safety requirements with modifications. Applies to glazed panels and glazing in windows and doors. |
| G1 Personal hygiene | G1/AS1 | Sets the numbers of sanitary fixtures to be provided for residential and non-residential buildings. Specifies: • methods of sanitary towel disposal • fixture construction and installation • location of sanitary fixtures • sanitary fixture requirements for people with disabilities. |
| G2 Laundering | G2/AS1 | Specifies laundry requirements for various defined uses. |
| G4 Ventilation | G4/VM1 | Specifies methods of: • measuring ventilation rates • demonstrating air purity. |
| G4/AS1 | Sets rules for and limitations on natural ventilation using opening windows.G5 Interior environment | |
| G5 Interior environment | G5/AS1 | Specifies methods of providing the heating requirements for habitable spaces, bathrooms and recreation rooms of retirement homes and early childhood centres. |
| G6 Airborne and impact sound | G6/VM1 | Specifies the performance requirements for airborne and impact sound transmission between abutting occupancies. |
| G6/AS1 | Specifies acceptable building element assemblies for minimising sound transmission. |
|
| G7 Natural light | G7/VM1 | Cites NZS 6703 Code of practice for interior lighting design, Appendix A as a method of assessing illumination. |
| G7/AS1 | Specifies rules for obtaining a satisfactory illuminance level in habitable rooms, but excludes bathroom, laundries and so on, for which there are no special requirements. | |
| G8 Artificial light | G8/AS1 | To provide a minimum illuminance of 20 lux per square metre of floor area to enable safe movement. |
| G9 Electricity | G9/AS1 | Cites NZECP 51 as an acceptable solution for dwellings. Cites NZECP 54 as a method of verifying performance for the installation of recessed luminaires. Sets rules for switches for use by people with disabilities. |
| G12 Water supplies | G12/VM1 | Cites AS/NZS 3500.1 and AS/NZS 3500.4 as a means of compliance. |
| G12/AS1 | Specifies rules for piped water supply systems. | |
| G13 Foul water | G3/VM1 | Cites BS 5572 as a means of compliance. |
| G13/AS1 | Sets out rules for sanitary plumbing for buildings up to three levels. Cites AS/NZS 3500.2 as a further Acceptable Solution. |
|
| H1 Energy efficiency | H1/VM1 | Specifies methods of determining the insulation requirements using: • NZS 4218 Energy efficiency - Housing and small building envelopes, section 3.3 • building performance index for housing • NZS 4243 Energy efficiency - Large buildings. |
| H1/AS1 |
Specifies a method for determining the required minimum R-values for all building envelope components including glazing. |
While not cited in Building Code compliance documents, AS 3740 Waterproofing of wet areas within residential buildings is a reference standard for the waterproofing of wet areas.