Fire-Rated Walls for Houses: NCC 900 mm Boundary Rule, FRL 60/60/60 and Party Walls (2025 Guide)
When a house wall must be fire-rated under the NCC: the 900 mm boundary and 1.8 m building-to-building rules in Housing Provisions 9.2.1, what FRL 60/60/60 means, openings and eaves near the boundary, separating walls to 9.3.1, service penetrations, garage exemptions, and the SA, NSW and WA variations.
When does a house wall need to be fire-rated under the NCC? For a Class 1 house the answer sits in Part 9 of the ABCB Housing Provisions, and it turns on two distances: 900 mm to an allotment boundary, and 1.8 m to another building on the same allotment. Inside those distances the external wall, and every opening in it, must be built to clause 9.2.3. A wall shared by two attached dwellings, the townhouse party wall, is governed by 9.3.1 instead, with its own rules about how far the wall climbs through the roof. This guide covers each rule, what FRL 60/60/60 means, the concessions near a boundary, service penetrations, the garage exemptions and the state variations.
The short answer
Under Housing Provisions clause 9.2.1, an external wall of a Class 1 building must comply with 9.2.3 if it is less than 900 mm from an allotment boundary (other than a boundary adjoining a road or other public space), or less than 1.8 m from another building on the same allotment (other than a Class 10 building associated with the house, or a detached part of the same house). Clause 9.2.3 then requires an FRL of not less than 60/60/60 tested from the outside, or masonry veneer with a 90 mm outer leaf, or 90 mm masonry, running from the footings to the underside of a non-combustible roof covering or eaves lining.
A separating wall between attached Class 1 dwellings needs the same 60/60/60 or 90 mm masonry under 9.3.1, must start at the footings or ground slab, and must extend to the underside of a non-combustible roof covering or, under a combustible roof covering, to at least 450 mm above it. A wall between a house and its own Class 10a garage is neither a separating wall nor caught by 9.2.1, so Part 9 asks nothing of it. These numbers are unchanged from NCC 2022, which matters because NSW, Queensland and South Australia stay on NCC 2022 until 1 May 2027.
1. What FRL 60/60/60 means
The NCC glossary defines a fire-resistance level (FRL) as the grading periods in minutes, determined under Specifications 1 and 2, for three criteria in a fixed order: structural adequacy, integrity and insulation. Each is tied to the AS 1530.4 furnace test. Structural adequacy is the ability to maintain stability and adequate load-bearing capacity. Integrity is the ability to resist the passage of flames and hot gases. Insulation is the ability to keep the unexposed face below the temperature limits in AS 1530.4. So 60/60/60 means the element stays standing, keeps flame and hot gas out, and keeps its cool side cool, for 60 minutes each. A dash means no requirement for that criterion; the glossary's example is 90/–/–. Part 9 uses the dash twice: a fire window in a boundary wall needs –/60/–, and a service opening in a separating wall needs –/60/60.
Non-combustible means not deemed combustible under AS 1530.1; NCC 2025 adds that the determination is by an Accredited Testing Laboratory, with a note that until the next NCC edition it need not be. Lightweight construction, which includes sheet and board materials and masonry less than 70 mm wide, must be tested to Specification 6 when used as a separating wall.
2. When an external wall must be fire-rated: 900 mm and 1.8 m
Clause 9.2.1(1) sets the two triggers. An external wall of a Class 1 building, and any openings in it, must comply with 9.2.3 if the wall is less than:
900 mm from an allotment boundary, other than the boundary adjoining a road alignment or other public space (9.2.1(1)(a)). The note to 9.2.4 explains why: roads, parklands, lakes and rivers are places where a building is unlikely to be built.
1.8 m from another building on the same allotment, other than a Class 10 building associated with the Class 1 building or a detached part of the same Class 1 building (9.2.1(1)(b)). Two houses on one title count; the owner's own garage or shed does not.
Clause 9.2.2(1) measures the distance from any point on the wall along a line at right angles from the boundary or the other building's wall, unobstructed by a wall that already complies with 9.2.3. Clause 9.2.2(2) is the concession designers rely on: where only part of a wall falls within the distance, only that part, with its openings, needs to be built to 9.2.3.
3. How the fire-rated external wall is built (9.2.3)
Clause 9.2.3(2) offers three deemed-to-satisfy constructions: an FRL of not less than 60/60/60 when tested from the outside; masonry-veneer construction with an external masonry veneer not less than 90 mm thick; or masonry construction not less than 90 mm thick.
Under 9.2.3(1) the wall must commence at the footings or ground slab (unless it starts above a separating wall complying with 9.3.1) and extend to the underside of a non-combustible roof covering or a non-combustible eaves lining. It may stop up to 200 mm short of the roof covering where the gap is sealed with a non-combustible fascia, gutter or flashing. A wall that cannot start at the footings needs a Performance Solution.
Openings must be protected by non-openable fire windows or other construction with an FRL of not less than –/60/–, or by self-closing solid-core doors not less than 35 mm thick (9.2.3(3)). Clause 9.2.3(4) allows an unprotected window in a non-habitable room at least 600 mm from the boundary or 1.2 m from another building on the allotment: up to 1.2 m² in a bathroom, laundry or toilet, or up to 0.54 m² elsewhere if it is a fixed steel-framed window in wired glass or is filled with translucent hollow glass blocks. Subfloor vents, roof vents, weepholes, control and construction joints, and pipe and conduit penetrations are exempt (9.2.3(5)).
4. Eaves, gutters and other encroachments near the boundary (9.2.9)
Within 900 mm of a boundary, or 1.8 m of another building on the same allotment, 9.2.9(3) permits non-combustible fascias, gutters and downpipes; light fittings, meters, aerials and antennas; pergolas, sun blinds and water tanks; unroofed terraces, landings, steps and ramps not more than 1 m high; and open carports complying with 9.2.8. A second group may come no closer than 450 mm to a boundary, or 900 mm to another building (9.2.9(4)): combustible fascias, gutters and downpipes; eaves with non-combustible roof cladding and non-combustible lining; and flues, chimneys, pipes, fuel tanks, cooling or heating appliances and other services. A deck is not an unroofed terrace and is never an allowable encroachment.
5. Separating walls between attached dwellings (9.3.1)
The glossary defines a separating wall as a wall common to adjoining Class 1 buildings. Clause 9.3.1(1) applies the same rules to a wall between a Class 1 building and a Class 10a building not associated with it, such as a neighbour's garage built against the house. The wall must:
Have an FRL of not less than 60/60/60, or be masonry not less than 90 mm thick (9.3.1(1)(a)). Unlike 9.2.3, the FRL is not qualified as "from the outside" and the masonry-veneer option is absent.
Commence at the footings or ground slab (9.3.1(1)(b)).
Extend to the underside of a non-combustible roof covering, or where the roof covering is combustible, to not less than 450 mm above it (9.3.1(1)(c)).
Be tested to Specification 6 if of lightweight construction (9.3.1(2)).
Where the wall stops under a non-combustible roof, 9.3.1(3) forbids timber or other combustible elements crossing it, except roof battens of 75 × 50 mm or less and roof sarking, and the gap between the wall head and the roof covering must be packed with mineral fibre or another suitable fire-resisting material. In a masonry-veneer house, 9.3.1(4) limits the gap between the separating wall and the veneer to 50 mm, packed. Eaves and verandahs open to the roof space and common to more than one dwelling need a non-combustible vertical lining (9.3.1(5)), and 9.3.4 fire-protects any horizontal projection within 1.8 m of the wall. Part 10.7 (sound insulation) applies to the same wall as well.
6. Services in a separating wall (9.3.2)
Any service opening not covered by the specific rules must have construction with an FRL of not less than –/60/60 (9.3.2(1)). A cable penetration (9.3.2(2)) must either match a prototype assembly tested to AS 4072.1 and AS 1530.4 at –/60/60, or be installed with a neatly formed opening no closer than 50 mm to any other service, no larger than 2,000 mm² for a single cable with a gap of no more than 15 mm, or 500 mm² otherwise, with the gap packed with mineral fibre. A switch, outlet or socket (9.3.2(3)) needs a tested system, or must not sit opposite any opening within 300 mm horizontally or 600 mm vertically on the other side, or must not extend beyond half the wall's thickness. In a hollow wall, 9.3.2(4) requires the cavity behind an outlet to be framed and packed unless a tested system is used. Back-to-back power points across a party wall are the classic non-compliance.
7. Garages, carports and the "same allotment" exemptions
A Class 10a garage or shed associated with the house is excluded from the 1.8 m test, and 9.3.1 applies only to a Class 10a building that is not associated with the house. The wall between a house and its own attached garage therefore carries no FRL requirement in Part 9. The rules bite when a garage sits between the house and something else. Clause 9.2.4(1) sends a garage between the house and a side or rear boundary to 9.2.5, a garage between the house and another building on the allotment to 9.2.6, and two garages belonging to different houses to 9.2.7. Each lists acceptable methods: keep the garage 900 mm from the boundary (or 1.8 m from the other building), keep the house 900 mm from the garage, or build the wall inside the distance to 9.2.3.
A carport is exempt under 9.2.8 if it has two or more sides open and at least one third of its perimeter open (a side is open if the adjacent roof covering is at least 500 mm from a building or boundary), a polycarbonate or non-combustible roof, non-combustible ceiling and wall cladding, no direct vertical support to the house, and non-combustible infill above the house wall where it shares the roof structure. Where a dwelling sits above someone else's garage, 9.4.1 requires the wall between them to be 60/60/60 tested from the other garage's side or 90 mm masonry, and 9.4.2 requires the floor to have a ceiling with a 60-minute resistance to the incipient spread of fire, an FRL of 30/30/30 from the underside, or a fire-protective covering such as 13 mm fire-protective grade plasterboard.
8. State variations: SA, NSW and WA
South Australia adds a third trigger to 9.2.1: a wall less than 3 m from a brush fence must comply with 9.2.3, measured in any direction (9.2.2(4)). SA 9.2.4 allows timber posts and roof beams on a carport or verandah at any distance from the boundary, and SA 9.2.8 extends the open-carport exemption to verandahs.
New South Wales replaces Part 9.4 for garage top dwellings. The NSW wall (NSW 9.4.3) needs only 30/30/30 tested from the non-associated garage side, or 90 mm masonry, and need not comply with 9.3.1; NSW 9.5.1 adds a heat alarm to AS 1603.3 in that garage.
Western Australia adds Part 9.6 for roofed outdoor areas (verandahs, alfresco areas and balconies). Unless it has a 9.2.3 wall, a side of the area must be at least 900 mm from a boundary or a Class 10 building, or 1.8 m from another building on the allotment. WA 9.6.2(3) allows 500 mm to a boundary or 1 m to another building for an open-sided area built of non-combustible materials and screened by a solid non-combustible fence at least 1,500 mm high with no more than 100 mm clearance underneath. Part 9.6 has no counterpart in the NCC 2022 Section 9 files.
9. What changed from NCC 2022, and which edition applies
Very little. Clauses 9.2.1, 9.2.3, 9.2.4, 9.2.9, 9.2.10, 9.3.1 to 9.3.4, 9.4.1 and 9.4.2, the SA variations to 9.2.1 and 9.2.4, and NSW 9.4.1 and 9.4.3 carry the same distances, FRLs and conditions in the NCC 2022 XML as in NCC 2025 v1.2. The visible 2025 changes are the Accredited Testing Laboratory wording in the non-combustible definition and WA's new Part 9.6.
Which edition applies depends on the state and the lodgement date. Victoria, Tasmania, Western Australia and the ACT apply NCC 2025 from 1 May 2026; New South Wales, Queensland and South Australia stay on NCC 2022 until 1 May 2027; the Northern Territory remains on NCC 2022. For the fire separation rules the outcome is the same either way, but the clause cited must match the edition in force; the state-by-state adoption guide tracks the dates. For the rest of the drawing set, see the stair requirements guide, the climate zones guide and the free NCC calculators.
Checklist
Every external wall within 900 mm of a side or rear boundary, or 1.8 m of another building on the allotment, marked on the site plan and measured at right angles (9.2.2).
Each affected wall specified as 60/60/60 from the outside, 90 mm masonry veneer or 90 mm masonry, footings to the underside of a non-combustible roof or eaves lining (9.2.3).
Openings shown as –/60/– fixed fire windows or 35 mm self-closing solid-core doors, or justified under the 9.2.3(4) concession.
Separating walls detailed to 9.3.1, with only 75 × 50 mm battens and sarking crossing and mineral fibre at the head; outlets offset and cavities packed to 9.3.2.
Every garage or shed checked for a position between the house and a boundary or another building, with a 9.2.5, 9.2.6 or 9.2.7 method nominated.
SA brush fence distances, NSW garage top dwelling rules, WA roofed outdoor area setbacks and the edition in force confirmed.
Check it against the source
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Sources: ABCB Housing Provisions 2025 (v1.2) clauses 9.1.1, 9.1.2, 9.2.1 to 9.2.10, 9.3.1 to 9.3.4, 9.4.1 and 9.4.2, the SA variations to 9.2.1, 9.2.2, 9.2.4, 9.2.8 and 9.2.9, NSW 9.4.1 to 9.4.3 and NSW 9.5.1, and WA 9.6.1 and 9.6.2; NCC 2025 Glossary (fire-resistance level, structural adequacy, integrity, insulation, non-combustible, lightweight construction, separating wall, allotment, fire-protective covering, resistance to the incipient spread of fire); NCC 2022 Housing Provisions Section 9 for the edition comparison; ABCB "NCC 2025 state and territory adoption information". Figures verified against the ABCB's published text on 4 September 2026. Diagram by AEC Assistant. This article is general guidance; the building surveyor or certifier for your project determines compliance.
