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NCC Volume Two Allowable Encroachments

What is an ‘Encroachment’?

An encroachment relates to the fire safety provisions in National Construction Code (NCC) Volume Two and is any construction between the external wall of the building and the allotment boundary, other than a boundary adjoining a road or other public space.

It can also be the external walls of two buildings on the same allotment or the external wall of the building and the vertical projection of an adjoining building on the same allotment.

The general aim of the fire safety provisions is to protect a Class 1 building from spread of fire via another building on the same site or via a neighbouring property. 

The Deemed-to-Satisfy (DTS) Provisions in NCC Part 3.7 Fire Safety satisfy this requirement by requiring fire-resisting external walls or separation. 


When an item of construction exists in the setback zone 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 eaves, gutters and downpipes. 

NCC Volume Two Clause contains controls to manage the risk of fire spread presented by different types of encroachments.

Clause and (d) divide the encroachment space into two ‘zones’:

  • Encroachments within 900 mm of the boundary, or 1.8 m of a non-associated building. These include:
    • non-combustible fascia’s, gutters and downpipes
    • light fittings, electricity or gas meters, aerials or antennas
    • pergolas, sun blinds or water tanks
    • unroofed terraces, landings, steps and ramps, not more than 1 m in height.
  • Encroachments up to, but not closer than, 450 mm from the boundary, or 900 mm from a non-associated building. These include:
    • eaves with non-combustible roof cladding and non-combustible lining
    • flues, chimneys, pipes, domestic fuel tanks, cooling or heating appliances or other services. (refer to figures 1 & 2 regarding allowable eave encroachments)


Figure 1


Figure 2

If you have an external wall of a building and the vertical projection of an adjoining building on the same allotment the allowable encroachments are non-combustible fascia’s, gutters and downpipes. (see figure 3).


Figure 3

Gable eave overhangs

It is sometimes not clear that when you have a wall within 900mm of a boundary that needs to be fire resistant, and whether it is permissible for the eave overhang at a gable end encroach within 450mm of the boundary?

It is somewhat unclear due to the NCC provisions stating that an encroachment is any construction between the external wall of the building and the allotment boundary etc.:

An encroachment is any construction between—

(i)the external wall of the building and the allotment boundary other than a boundary adjoining a road or other public space;

Though in this situation there is no need for the eave encroachment to comply as the eave section facing the boundary shown is not between a wall and a boundary and the front and the sides of the eave would generally be more than 450mm from a boundary or facing a road.

The following diagram shows this situation in a plan view.


Figure 4

It is good to note that the encroachment provisions are 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 refers. 

It’s also important to consider any State or Territory requirements for siting of buildings in relation to setbacks as these will also need to be complied with as well as the NCC allowable encroachment provisions.


To find out more, contact HIA's Workplace Services team

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