Class 10a Buildings: NCC Rules for Sheds, Garages and Carports, and Fire Separation from the Boundary (2025 Guide)
What Class 10a, 10b and 10c mean in the NCC, which parts of the Code apply to a shed, garage or carport, and when a Class 10a near a boundary or another building needs a fire-rated wall under Housing Provisions 9.2.4 to 9.2.8. Every protection method the Code accepts, the open-carport test, garages under dwellings and the South Australian variations, with a checker that draws your site.
A garage, carport or shed is a Class 10a building under the National Construction Code (NCC). Many of the Code's rules for houses do not reach it, and the fire rules that do are mostly about protecting the house beside it. Put a garage within 900 mm of a side fence, between the house and the boundary, and a fire could travel from the boundary to the house through the garage. Housing Provisions 9.2.4 to 9.2.7 close that path.
This guide sets out what Class 10a, 10b and 10c are and which parts of the NCC apply to them. It then lists every protection method the Housing Provisions accept, with the open-carport exemption, garages under dwellings and the South Australian variations. The checker in section 10 draws your site and the wall to rate. For the house's own walls near a boundary, see our guide to the 900 mm boundary rule.
In one minute
Class 10 is non-habitable. 10a is a building such as a private garage, carport or shed; 10b a structure such as a fence, mast, retaining wall or swimming pool; 10c a private bushfire shelter (A6G11).
A Class 10a near a boundary or another building calls up a list of methods. Near a side or rear boundary: 9.2.5. Near another building on the allotment: 9.2.6. Garages of two houses between them: 9.2.7 (9.2.4(1)). A road boundary is left out.
Distance can settle it. Nothing is needed when the Class 10a is 900 mm or more from the boundary, or the house is 900 mm or more from it (9.2.5(1)(a), (d)). For another building the figure is 1.8 m (9.2.6(1)(a), (d)).
Otherwise a wall (in some methods, two) is built to 9.2.3: FRL 60/60/60 tested from the outside, or 90 mm masonry or masonry veneer. It may be the garage's boundary wall, its wall facing the house, or the house's wall facing it (9.2.5(1)(b) to (i)).
An open carport is exempt when it meets all of 9.2.8, including two or more open sides. A side is open only where the roof is 500 mm or more from the boundary or another building.
1. What Class 10 covers
NCC 2025 sorts every building into a class. Class 10 is the one people do not live in: "A Class 10 building or structure is non-habitable" (A6G11(1)). It has three sub-classifications (A6G11(2)):
Class 10a "is a non-habitable building including a private garage, carport, shed or the like."
Class 10b "is a structure that is a fence, mast, antenna, retaining wall or free-standing wall or swimming pool or the like."
Class 10c "is a private bushfire shelter."
The glossary defines a private garage, for Volume Two, as "any garage associated with a Class 1 building", or a separate single-storey garage of up to 3 vehicle spaces associated with another building. A private bushfire shelter is "associated with, but not attached to, or part of a Class 1a dwelling". A swimming pool includes "a bathing or wading pool, or spa". There is no glossary definition of a carport: the Code tests one by its sides, in 9.2.8 (section 7).
The explanatory note to A6G11 settles the edge cases. A habitable outbuilding, such as a sleepout or a detached entertainment room, is part of the house. A small hobby toolshed is Class 10, and a Class 10 building can stand alone, like a toilet block in a park. Some states and territories exempt small Class 10 buildings from needing a building permit.
2. Which parts of the NCC apply to a Class 10 building
Volume Two holds the requirements for Class 1 and 10a buildings, certain Class 10b structures and Class 10c shelters (A1G2). Access for people with a disability in Class 10a buildings and Class 10b pools is in Volume One (A1G1). A Class 10 building picks up the clauses that name it.
| Topic | What the Code asks of a Class 10 building | Clause |
|---|---|---|
| Structure | Built to Housing Provisions Section 2, or Volume Two H1D3 to H1D12. The explanatory note to 2.2.3 puts an isolated minor Class 10a or 10b at Importance Level 1, and one associated with a house at Importance Level 2. | Vol Two H1D2; 2.2.3 |
| Masonry garage or shed | A single-storey Class 10a may have single-leaf masonry walls not less than 90 mm thick: up to 9 m in the direction of the roof span and 2.7 m high, with engaged piers, no spreading thrust from the roof, in wind class N2 or lower. | 5.4.2(2) |
| Termites | Applies where a Class 1 or 10 building is in an area of known subterranean termite risk and a primary building element is susceptible. | 3.4.1(1) |
| Slab vapour barrier | Under a Class 10 slab only where it is continuous with the slab of the house. | 4.2.8(1) |
| Weatherproofing | Not applied to a Class 10 building, except where its construction contributes to the weatherproofing of the house. | Vol Two H2P1(2), H2P2(a), H2D4(1)(b) |
| Fire separation | Protects the house where a Class 10a is near a boundary or another building, or belongs to another dwelling. | 9.2.4 to 9.2.8; 9.3.1; Part 9.4 |
| Smoke alarms | A Class 10a private garage above or below the house counts as part of it. Where a smoke alarm there would give spurious alarms, another suitable alarm may be used, with smoke alarms elsewhere in the house. | Vol Two H3D6(2); 9.5.1(b) |
| Energy efficiency | An attached Class 10a either has fabric meeting the house's thermal performance or is separated from the house by construction that does. Lighting in an associated Class 10a is limited to 3 W/m². | 13.2.7(1); 13.7.6(1)(c) |
| Bushfire | A Class 10a associated with a house in a designated bushfire prone area is designed for bushfire too. Building it to AS 3959:2018, or to the NASH Standard for steel-framed construction in bushfire areas, satisfies the Performance Requirement. | Vol Two H7P5; H7D4(2) |
| Class 10b and 10c | A swimming pool with more than 300 mm of water needs a barrier; Queensland and the Northern Territory regulate pool barriers under their own laws. A private bushfire shelter has a Performance Requirement and no Deemed-to-Satisfy Provisions. | Vol Two H7P1, H7D2(1); H7P6 |
| Access | A Class 10a in an accessible area used by the public, with a sanitary facility, change room or shelter, needs access to and within them. | Vol One D4D2(10)(a) |
NCC 2025 Volume Two and the ABCB Housing Provisions, paraphrased; Housing Provisions clauses unless marked. The termite rules are in our termite protection guide and the bushfire levels in our BAL guide.
One structural rule matters for the fire rules. A single-leaf 90 mm masonry wall is allowed for a single-storey Class 10a within the limits of 5.4.2(2), and 90 mm masonry is one of the three constructions 9.2.3(2) accepts as fire-resisting. A single-skin brick garage wall on the boundary can do both jobs.
3. Why a garage near the boundary matters (9.2.4)
Clause 9.2.1 rates a house wall less than 900 mm from a side or rear boundary, or less than 1.8 m from another building on the allotment. That test leaves out "a Class 10 building associated with the Class 1 building" (9.2.1(1)(b)). So the wall between a house and its own garage carries no rating for its own sake.
The gap is the path through the garage. Clause 9.2.4(1) requires the house to be protected by a method in:
9.2.5, where a Class 10a is "between or adjacent to" the house and a boundary that is not a road or other public space;
9.2.6, where a Class 10a is between or adjacent to the house it is associated with and another building on the same allotment;
9.2.7, where two or more Class 10a buildings on the same allotment are between and associated with different houses.
The explanatory note gives the intent: to stop fire spreading from the allotment boundary, the fire-source feature, to the house via a Class 10a. A Class 10a not directly and wholly between the two can still carry fire, which is why the clause says "or adjacent to".
Roads, parklands, lakes and rivers are left out because buildings are unlikely there, so a street frontage needs no rating. Separately, a Class 10a must not significantly increase the risk of fire spread between Class 2 to 9 buildings (9.2.4(2)).
4. A Class 10a near a boundary or another building (9.2.5 and 9.2.6)
Clause 9.2.5 lists nine methods, (a) to (i). Clause 9.2.6 lists eight, (a) to (h), for the same layouts with another building in place of the boundary. Every 9.2.5 distance is 900 mm and every 9.2.6 distance is 1.8 m. One method is enough.
| Method | 9.2.5: side or rear boundary | 9.2.6: another building |
|---|---|---|
| Keep the Class 10a clear of the boundary or other building | (a): 900 mm or more | (a): 1.8 m or more |
| Keep the house clear of the Class 10a | (d): 900 mm or more | (d): 1.8 m or more |
| Rate the Class 10a's wall facing the boundary or other building | (b); (f) when beside the house | (b); (f) when beside the house |
| Rate the Class 10a's wall facing the house | (c); (g) when beside the house | (c); (g) when beside the house |
| Rate the house's wall facing the Class 10a | (e); (h) when beside the house | (e) |
| Rate both the house's and the Class 10a's walls inside the distance | (i) | (h) |
Housing Provisions 9.2.5(1) and 9.2.6(1), paraphrased. Each wall that is rated is built to 9.2.3. "Beside" follows the figures: Figures 9.2.5b to 9.2.5e draw the Class 10a directly between the house and the boundary, and Figures 9.2.5f to 9.2.5i draw it set to one side.
Methods (a) and (d) are the quiet ones. A garage within 900 mm of the boundary needs nothing when the house is 900 mm or more from it. A detached garage on the rear fence with a 1 m path to the house needs no rated wall.
When neither distance works, choose the wall. For an attached garage near a side boundary it is usually the garage's boundary wall, the layout of Figures 9.2.5a and 9.2.5b. For a detached garage close to both, the house wall facing it can be simpler. Where the house wall is itself within 900 mm of the boundary, 9.2.1 rates it anyway, and method (i) pairs it with the garage's boundary wall.
In 9.2.6 the Code's figures label the other building "other class of building on allotment". The house wall facing it keeps its own 1.8 m test under 9.2.1(1)(b).
5. Two garages between two houses (9.2.7)
Where two or more Class 10a buildings on one allotment sit between different houses, as with two dwellings on one title, 9.2.7 applies. Its eight methods come down to five:
The garages are at least 1.8 m apart (9.2.7(1)(a)).
Each garage is at least 900 mm from each house (9.2.7(1)(c)).
The garages' facing walls are built to 9.2.3 (9.2.7(1)(b) and (f)).
Each garage's wall facing a house is built to 9.2.3 (9.2.7(1)(d) and (g)).
Joined garages are divided by a wall complying with 9.3.1 (9.2.7(1)(e) and (h)).
The 9.3.1 wall is the townhouse party wall: FRL 60/60/60 or 90 mm masonry, from the footings or slab to the underside of a non-combustible roof covering, or 450 mm above a combustible one (9.3.1(1)). Only roof battens of 75 × 50 mm or less and sarking may cross it (9.3.1(3)), and a service opening needs construction of –/60/60 (9.3.2(1)).
The same wall is required in its own right between a house and a Class 10a not associated with it, such as a neighbour's garage built against the house (9.3.1(1)).
6. How the fire-rated wall is built (9.2.3)
A wall required by 9.2.4 is built like a house wall required by 9.2.1, because 9.2.3 covers both. It has an FRL of not less than 60/60/60 tested from the outside, or is masonry veneer with a 90 mm outer leaf, or 90 mm masonry (9.2.3(2)). It runs from the footings or slab to the underside of a non-combustible roof covering or eaves lining (9.2.3(1)). Our FRL guide explains 60/60/60, and the 900 mm rule guide covers the details at the eaves.
Openings in the rated wall are non-openable fire windows or other construction of –/60/–, or self-closing solid-core doors at least 35 mm thick (9.2.3(3)). Distances are taken at right angles, and only the part of a wall within the distance needs to comply (9.2.2(1), (2)).
For a Class 10a building required to comply with 9.2.4, projecting construction is an encroachment under 9.2.9 (9.2.9(2)(a)). Non-combustible fascias, gutters and downpipes may come within 900 mm of the boundary. Combustible ones, and eaves with non-combustible roofing and lining, stop 450 mm short of it (9.2.9(3), (4)).
7. Open carports (9.2.8)
A Class 10a carport is exempt from 9.2.4(1) if it meets every one of these conditions (9.2.8(1)):
Two or more sides are open, and at least one third of its perimeter is open (a).
A side counts as open only if the roof covering next to it is at least 500 mm from another building on the allotment or from the boundary (b).
The roof covering is polycarbonate or non-combustible (c).
Any ceiling lining and wall cladding, gables included, is non-combustible (d).
It gives no direct vertical support to any part of the house (e).
Where it shares the house's roof and has no ceiling, the opening between the top of the house wall and the roof covering is infilled with non-combustible material, or construction clad with it on the carport side (f).
The explanatory note adds the rule that catches people: "A side of a carport enclosed by a vehicle access door is not considered to be an open side." Fit a tilt or roller door and that side no longer counts as open. An open carport that meets 9.2.8 is also an allowable encroachment within 900 mm of a boundary (9.2.9(3)(e)).
8. Garages under dwellings and other special cases
A house over its own garage. Part 9 sets no fire rating between them. For smoke alarms, a Class 10a private garage above or below a Class 1 building counts as part of it (Volume Two H3D6(2)), and the explanatory note says a storey of only car parking still gets an alarm. Where a smoke alarm there would give spurious alarms, another suitable alarm may be used, with smoke alarms elsewhere in the house (9.5.1(b)).
A dwelling over someone else's garage. Part 9.4 applies. The wall between the dwelling and that garage, and between the dwelling's own garage and the other garage, is 60/60/60 tested from the other garage's side, or 90 mm masonry (9.4.1). The floor between has 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 on a combustible or metal floor (9.4.2(1)).
New South Wales writes its own Part 9.4 for garage top dwellings. Its wall needs 30/30/30 tested from the non-associated garage side, or 90 mm masonry, and need not comply with 9.3.1 (NSW 9.4.3). NSW also requires a heat alarm in the non-associated garage, interconnected with the dwelling's smoke alarms (NSW 9.5.1(2)).
9. South Australia and Western Australia
South Australia varies the Class 10a clauses directly:
A carport or verandah may have timber posts and timber roof support beams regardless of their distance from the boundary (SA 9.2.4(3)).
A Class 10b brush fence must not be built within 3 m of a house unless the part of the house within 3 m complies with 9.2.1, 9.2.2, 9.2.3 and 9.2.9 (SA 9.2.4(4); SA 9.2.1(1)(c)). Brush fence distances are measured in any direction (SA 9.2.2(4)).
SA 9.2.8 replaces the open-carport clause. It extends the exemption to verandahs and gives a second route: house walls within 2 m of the boundary, or within 4 m of another house, made fire-resisting to the underside of a non-combustible roof covering or ceiling lining (SA 9.2.8(1)(a)(ii)).
Western Australia's Part 9.6 for roofed outdoor areas, such as alfresco areas, ties into the same clauses. A side within 900 mm of a Class 10 building is protected in accordance with 9.2.5. A side within 1.8 m of a Class 10a building is protected in accordance with 9.2.6 (WA 9.6.2(1)).
10. Check your garage, carport or shed
Choose where the Class 10a sits, then set the distances. Choose the wall you would rather rate, and tick the boxes for an open carport or a site in South Australia. The plan redraws with the wall to rate in the key colour and the other accepted walls dashed. The headline gives the answer, the verdict names the clause and method, and the cards give each option with its figure.
Worked examples
A double garage attached to the house, 450 mm from the side boundary. Under 900 mm from the boundary, (a) fails; attached, (d) fails. One wall goes to 9.2.3, usually the garage's boundary wall in 90 mm masonry or 60/60/60 construction (9.2.5(1)(b), Figure 9.2.5b). A window in it is a non-openable –/60/– fire window (9.2.3(3)). A gutter on that side is closer than 450 mm to the boundary, so it must be non-combustible (9.2.9(3), (4)).
The same garage moved to 1 m from the boundary. Method (a) is met (9.2.5(1)(a)) and no wall needs rating.
A detached garage on the rear fence, 1.2 m from the house. The garage is on the boundary, but the house is more than 900 mm from it, so method (d) is met (9.2.5(1)(d)). Narrow the path to 600 mm and one wall must be rated: the garage's rear wall, its wall facing the house, or the house's wall facing it (9.2.5(1)(b), (c), (e)).
Two dwellings on one title with joined garages between them. The garages are under 1.8 m apart and attached to their houses, so 9.2.7 applies. Either a 9.3.1 separating wall goes between the garages (9.2.7(1)(e)), or each garage's wall facing its house is rated (9.2.7(1)(d)). Set the garages 1.8 m apart and neither is needed (9.2.7(1)(a)).
A 3.2 m by 6 m carport against the house, 300 mm from the boundary. The house side and the boundary side (under 500 mm) are closed. The front and back are open: 3.2 + 3.2 = 6.4 m of an 18.4 m perimeter, 35%, at least a third. With a polycarbonate roof, non-combustible cladding and no support to the house, and with the other conditions of 9.2.8(1) met, it is exempt. Add a tilt door and only one side is open, so 9.2.5 applies.
A garden shed on the back fence, 8 m from the house. Nothing is needed: the house is well over 900 mm away (9.2.5(1)(d)), and its own shed is left out of its 1.8 m test (9.2.1(1)(b)).
Common mistakes
Rating the wall between the house and its own garage by default. Part 9 asks nothing of it unless the garage is near a side or rear boundary or another building, and even then it is one option (9.2.5(1)(c), (e)).
Forgetting the house-to-garage test. A garage within 900 mm of the boundary needs nothing when the house is 900 mm or more from it (9.2.5(1)(d)).
Counting a side with a door, or a roof near the fence, as open. A vehicle door closes a side, and a side is open only where the roof covering is 500 mm or more from the boundary or another building (9.2.8(1)(b) and its note).
Leaving openings in the rated garage wall unprotected. A window or door in a wall required by 9.2.4 is protected under 9.2.3(3), as in a house wall.
Treating the street frontage as a boundary. 9.2.4 leaves out a boundary with a road or other public space, so a garage built to the front boundary needs no rating for it.
Where to read the source
NCC 2025 is free to read on the NCC website. The class definitions are in Volume Two A6G11 and the scope of Volume Two in A1G2, with the glossary in Schedule 1. The fire separation clauses are Housing Provisions 9.2.1 to 9.2.9 with their figures, 9.3.1, 9.3.2, Part 9.4 and 9.5.1, with the state variations printed beside them. AS 3959:2018 is purchased from Standards Australia.
Inside AEC Assistant the Code text is searchable by clause, and on a paid plan the Standards are too. Ask which wall a garage 300 mm from the side boundary needs to rate, and the answer comes back with the clause it was read from. This article is general guidance. The building surveyor or certifier for your project determines compliance.
Questions this guide answers
What is a Class 10a building?
A non-habitable building such as a private garage, carport or shed (NCC A6G11(2)(a)). Class 10b covers structures such as fences, masts, antennas, retaining or free-standing walls and swimming pools, and Class 10c is a private bushfire shelter. A habitable outbuilding such as a sleepout is part of the house, not Class 10.
Does a garage on the boundary need a fire-rated wall?
When it is between or beside the house and a side or rear boundary and less than 900 mm from that boundary, Housing Provisions 9.2.5 needs a protection method unless the house is at least 900 mm from the garage. The usual method is to build the garage's boundary wall to 9.2.3: an FRL of 60/60/60 tested from the outside, or 90 mm masonry or masonry veneer. A boundary to a road or public space is excluded.
Does a shed near the boundary need to be fire rated?
Not on its own. Part 9.2 protects the house, so a shed needs a rated wall only when it sits between or beside the house and a side or rear boundary or another building. It needs nothing when it is 900 mm or more from the boundary, or the house is 900 mm or more from it (9.2.5(1)(a) and (d)); for another building both distances are 1.8 m (9.2.6(1)(a) and (d)).
Does a carport need a fire wall on the boundary?
Not if it is an open carport under 9.2.8: two or more sides open and at least one third of its perimeter open, a polycarbonate or non-combustible roof, non-combustible linings and cladding, no vertical support to the house, and infill above the house wall where it shares the roof without a ceiling. A side counts as open only where the roof covering is at least 500 mm from the boundary or another building, and a side closed by a vehicle door is not open.
Does the wall between a house and its attached garage need to be fire rated?
Not for its own sake. A Class 10 building associated with the house is left out of the 1.8 m test in 9.2.1, and the separating wall rules of 9.3.1 apply only to a Class 10a that is not associated with the house. That wall becomes one option among several when the garage sits within 900 mm of a side or rear boundary (9.2.5).
