National Construction Code

Allowable encroachments - how close is too close?

02/12/2020
Homes in residential suburb

Did you know that NCC Volume Two contains requirements relevant to plumbers, gas-fitters and air-conditioning installers?

An aim of Performance Requirement P2.3.1 is to protect Class 1 buildings from fire spread via another building on the same site (other than an associated building) or via a neighbouring property. Deemed-to-Satisfy (DTS) Provisions in Part 3.7 satisfy P2.3.1 by requiring fire-resisting external walls or separation. When construction exists between an external wall and either the property boundary or another building, that construction is an encroachment and must meet certain parameters so it won't compromise the prevention of fire spread.

Common encroachments include building service units, such as water heaters and air-conditioning units, and building elements such as gutters and downpipes. In order to maintain compliance with P2.3.1, 3.7.2.7 contains controls, subject to the various risk of fire spread presented by different types of encroachments.

3.7.2.7(c) and (d) divide the encroachment space into two zones:

  • Zone 1 (3.7.2.7(c)): within 900 mm of the boundary, or 1.8 m of a non-associated building, with only listed encroachments permitted in this zone.
  • Zone 2 (3.7.2.7(d)), up to, but not closer than, 450 mm from the boundary, or 900 mm from a non-associated building, with listed encroachments permitted in this zone.

Encroachments that present less risk, such as non-combustible downpipes, are permitted in Zone 1. Encroachments that present more risk, such as air-conditioning units and water heaters, must be located in Zone 2.

Diagram showing what is not an encroachment

To clarify, 3.7.2.7 is not applicable to subterranean pipes (such as drainage pipes) because, being below ground, they are not located between the wall and the boundary. A garden tap is also not an encroachment because it is not construction to which 3.7.2.7(a) refers.

It’s important to remember that construction between an external wall and the property boundary, or a non-associated building, may present a level of risk, and if you are a plumber, gas-fitter or air-conditioning installer, the requirements of 3.7.2.7 may apply to your work.

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