NCC 2022 Volume One - Building Code of Australia Class 2 to 9 buildings


Part G2 Boilers, pressure vessels, heating appliances, fireplaces, chimneys and flues

Part G2 Boilers, pressure vessels, heating appliances, fireplaces, chimneys and flues

Introduction to this Part

This Part is intended to reduce the risk to building occupants from the operation, malfunction or failure of boilers, pressure vessels and combustion appliances including components such as fireplaces, chimneys, flues, chutes, hoppers and the like.

Explanatory information

Part G2 does not contain requirements for gas heaters, gas appliances and associated flues.


The Objective of this Part is to—

  1. safeguard occupants from illness or injury caused by—
    1. fire from combustion appliances installed within a building; and
    2. malfunction of a boiler or pressure vessel installed within a building; and
  2. protect a building from damage caused by the malfunction of a boiler or pressure vessel installed within.

Functional Statements

Combustion appliances using controlled combustion located in a building are to be installed in a way which reduces the likelihood of fire spreading beyond the appliance.

Boilers and pressure vessels located in a building are to be installed in a manner which will provide adequate safety for occupants.

Performance Requirements

Where provided in a building, a combustion appliance and its associated components, including an open fire-place, chimney, flue, chute, hopper or the like, must be installed—

  1. to withstand the temperatures likely to be generated by the appliance; and
  2. so that it does not raise the temperature of any building element to a level that would adversely affect the element’s physical or mechanical properties or function; and
  3. so that hot products of combustion will not—
    1. escape through the walls of the associated components; and
    2. discharge in a position that will cause fire to spread to nearby combustible materials or allow smoke to penetrate through nearby windows, ventilation inlets, or the like.

When located in a building, boilers and pressure vessels must be installed to avoid, during reasonably foreseeable conditions, the likelihood of—

  1. leakage from the vessel which could cause damage to the building; and
  2. rupture or other mechanical damage of the vessel which could cause damage to the building or injury to occupants.

Verification Methods

Compliance with G2P1(a) and G2P1(b) is verified when—

  1. components used within an appliance and its installation are constructed from—
    1. heat-resistant materials for maximum operating temperatures not less than 600℃, where the material complies with (c); or
    2. heat-tolerant materials for maximum operating temperatures more than 150℃ and less than 600℃, where the material complies with (c); and
  2. the building elements surrounding the appliance maintain their designed function and material properties inclusive of a full range of thermal movements when exposed to the heat effects of the appliance; and
  3. a sample of the material is tested to the maximum operating temperature, specified in (a)(i) or (a)(ii) for a minimum of 96 hours; and
  4. the tested sample, when allowed to cool, is free from—
    1. visible cracks and fractures; and
    2. visible indication of de-lamination; and
    3. linear distortion in excess of the equivalent of 10 mm per metre, and
    4. deterioration of the appearance of any surface finish, when compared to an unheated sample.

Deemed-to-Satisfy Provisions

(1) Where a Deemed-to-Satisfy Solution is proposed, Performance Requirements G2P1 and G2P2 are satisfied by complying with G2D2 to G2D4.

(2) Where a Performance Solution is proposed, the relevant Performance Requirements must be determined in accordance with A2G2(3) and A2G4(3) as applicable.

The installation of a stove, heater or similar appliance in a building must comply with:

  1. Domestic solid-fuel burning appliances — installation: AS/NZS 2918.
  2. For boilers and pressure vessels: Specification 30.

An open fireplace, or solid-fuel burning appliance in which the fuel-burning compartment is not enclosed, must have—

  1. a hearth constructed of stone, concrete, masonry or similar non-combustible material so that—
    1. it extends not less than 300 mm beyond the front of the fireplace opening and not less than 150 mm beyond each side of that opening; and
    2. it extends beyond the limits of the fireplace or appliance not less than 300 mm if the fireplace or appliance is free-standing from any wall of the room; and
    3. its upper surface does not slope away from the grate or appliance; and
    4. combustible material situated below or around the external edge of the hearth, but not below that part required to extend beyond the fireplace opening or the limits of the fireplace, is not less than 150 mm from the upper surface of the hearth; and
  2. walls forming the sides and back of the fireplace up to not less than 300 mm above the underside of the arch or lintel which—
    1. are constructed in 2 separate leaves of solid masonry with a total combined thickness not less than 180 mm, excluding any cavity; and
    2. do not consist of concrete block masonry in the construction of the inner leaf; and
  3. walls of the chimney above the level referred to in (b)—
    1. constructed of masonry units with a net volume, excluding cored and similar holes, not less than 75% of their gross volume, measured on the overall rectangular shape of the units, and with an actual thickness of not less than 100 mm; and
    2. lined internally to a thickness of not less than 12 mm with rendering consisting of 1 part cement, 3 parts lime, and 10 parts sand by volume, or other suitable material; and
  4. suitable damp-proof courses or flashings to maintain weatherproofing.

(1) If an incinerator is installed in a building, any hopper giving access to a charging chute must be—

  1. non-combustible; and
  2. gas-tight when closed; and
  3. designed to return to the closed position after use; and
  4. not attached to a chute that connects directly to a flue unless the hopper is located in the open air; and
  5. not located in a required exit.

(2) A room containing an incinerator must be separated from other parts of the building by construction with an FRL of not less than 60/60/60.