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Acoustic design in New Zealand

This section provides information on New Zealand Building Code requirements.

New Zealand Building Code requirements

Clause G6 (Airborne and Impact Sound) of the Building Code aims to safeguard people from illness or loss of amenity as a result of undue noise being transmitted between abutting occupancies.

The clause requires building elements that are common between occupancies to be constructed so that they prevent undue noise transmission from other occupancies or common spaces to habitable spaces of household units.

Clause G6 (1992) requires separating wall, floor and ceiling elements to have a sound transmission class (STC) of not less than 55 dB. In addition, floors must have an impact insulation class (IIC) rating of no less than 55.

Verification Method G6/VM1 in the Building Code states that the performance for airborne sound may be verified in accordance with ASTM E 336 (measurement) and ASTM E 413 (rating).

The performance for impact sound insulation may be verified using the International Organization for Standardization ISO 140: Part VII (measurement) and ASTM E 989 (rating).

Verification Method G6/VM1 states that field (F) test results shall be within 5 dB of the performance requirements, and the general market interpretation of this is that onsite measurements of field sound transmission class (FSTC) 50 and FIIC 50 satisfy the requirements of the Building Code.

The scope of the 1992 requirements is limited to habitable spaces within apartments intended for permanent living.

No requirements apply to other applications, such as non-habitable spaces within apartments (for example, bathroom-to-bathroom), temporary accommodation (hotels, motels, boarding houses), retirement centres, care facilities and offices.

In addition, the 1992 requirements do not apply to external (or environmental) sound, which often causes complaints by apartment dwellers. Another area of common complaint is plumbing noise, and this is not dealt with adequately in the 1992 Building Code provisions.

The provisions for noise control in applications outside the scope of the Building Code are entirely discretionary and often overlooked. The following steps are recommended:

  • define legal requirements (Building Code and district plan requirements)
  • identify noise sources, loudness and direction, including external, plant rooms, services
  • decide the level of acoustic comfort required
  • determine building element performance in terms of SCT and IIC ratings
  • select appropriate construction types and systems
  • consider flanking paths (window-to-window, ceiling plenum, across floor, services)
  • implement quality assurance and compliance plans (check lists, expert inspection, site testing).

Table 1 provides indicative minimum levels of noise control for different applications.

Acoustic consultancy practices are often involved in determining minimum levels of acoustic comfort depending on building use and occupancy, setting design criteria, and providing assistance with building design and performance or compliance testing.

The involvement of acoustic experts at an early concept stage of a project is recommended and sometimes essential for ensuring satisfactory outcomes.

Decisions regarding noise control can greatly affect the choice of building materials and construction details, location, size and type of external openings, doors and services.

Building services can be a significant noise nuisance and once a building has been completed it is often too late or too expensive to address noise concerns.

It is essential to consider the location and isolation of plumbing and heating, and ventilation and air conditioning services at the building design stage.

 

Minimum levels of noise control for different applications - Printable PDF

Source: Timber Design Guide 2007.