Fire walls and fire compartments in industrial warehouses
By Brenscot Builders | Last reviewed September 2026
Warehouse owners want open, uninterrupted floor space. The National Construction Code (NCC) limits how large an undivided space can be, so that a fire is contained to a size the fire brigade can deal with. Fire walls are how those two aims are reconciled. They are also one of the design decisions most often left too late.
This article explains what a fire compartment is, the size limits, what a fire wall has to do, and how to weigh fire walls against sprinklers.
This article refers to NCC 2022 Volume One, which applies in Queensland until NCC 2025 commences on 1 May 2027.
The short answer
A Type C warehouse (most single-storey warehouses) can have fire compartments of up to 2,000 m2 in floor area and 12,000 m3 in volume. A bigger building must be divided by fire walls into compartments within those limits, built to a higher type of construction, designed as a "large isolated building", or justified by a performance solution. In multi-unit buildings, the walls between units normally serve as the fire walls.
What is a fire compartment?
A fire compartment is either the whole building, or a part of it separated from the rest by walls and floors with the fire resistance required for a fire wall, with any openings protected. If there are no fire walls, the whole building is one compartment.
NCC Table C3D3 sets the maximum size of a compartment for Class 6, 7 and 8 buildings (shops, warehouses and factories):
| Type of construction | Maximum floor area | Maximum volume |
|---|---|---|
| Type A | 5,000 m2 | 30,000 m3 |
| Type B | 3,500 m2 | 21,000 m3 |
| Type C | 2,000 m2 | 12,000 m3 |
Both limits apply. In a tall warehouse, volume is reached first. At an average internal height of 9 m, a Type C compartment reaches 12,000 m3 at about 1,333 m2 of floor area (12,000 divided by 9). How the type of construction is determined is explained in construction Types A, B and C.
What a fire wall has to do
Under NCC clause C3D8 and Specification 5, a fire wall must:
- Achieve the required FRL. For Class 7b and 8 buildings this is 90/90/90 in Type C construction and 240/240/240 in Types A and B. The numbers are minutes of structural adequacy, integrity and insulation.
- Be continuous. It must extend to the underside of the roof covering. Building elements must not pass through or cross it unless the wall's fire resistance is maintained. Small roof battens and sarking are the exceptions.
- Have protected openings. Doorways in a fire wall must not total more than half the length of the wall (clause C4D6). Each doorway must be protected by self-closing or automatic-closing fire doors or fire shutters. A single door or shutter must have an FRL not less than that required for the wall, except that its insulation rating need only be 30 minutes (for example, -/90/30 in a 90/90/90 wall). The NCC also allows two doors or shutters, one each side, each with half the wall's FRL.
- Have sealed penetrations. Pipes, cables and ducts passing through must be sealed with tested fire-stopping systems.
In warehouses, fire walls are usually concrete tilt or precast panels, designed by the structural engineer for the required FRL. The steel roof structure is detailed so that it does not carry a fire across the top of the wall. See wall systems compared.
When fire walls come into a warehouse design
- The building is larger than one compartment allows. Floor area or volume exceeds the Table C3D3 limits for the type of construction.
- Multi-unit buildings. Walls between units are built as fire walls, so that each unit is a separate compartment within the limits. They usually sit on the future lot boundaries.
- Different uses in one building. Parts with different classifications may need to be fire-separated from each other.
- Keeping a compartment under a services threshold. Some fire services requirements depend on compartment size, so dividing a building can change what is required. This needs care. See the sprinkler section below.
A separate rule applies near boundaries. In Type C construction, external walls less than 3 m from a fire-source feature (a side or rear boundary, the far side of an adjoining road, or another building on the site) need an FRL under Specification 5, whatever the internal layout. Types A and B have stricter requirements.
The alternatives to fire walls
A higher type of construction
Building to Type B or Type A increases the compartment limits, but brings much higher fire-resistance requirements for walls, columns and other elements.
The large isolated building provisions
Under clause C3D4, a building can exceed the Table C3D3 limits as a single compartment if it meets these conditions:
| Building size | Conditions |
|---|---|
| Up to 18,000 m2 and 108,000 m3 | Class 7 or 8, no more than 2 storeys, with open space at least 18 m wide all around the building, which must include the perimeter vehicular access; OR sprinklers throughout and perimeter vehicular access |
| Over 18,000 m2 or 108,000 m3 | Sprinklers throughout and perimeter vehicular access |
Perimeter vehicular access (clause C3D5) means a continuous path that lets fire trucks travel forward from the public road around the whole building. It must be at least 6 m wide, with its far edge no more than 18 m from the building, and built to carry fire brigade vehicles. Where open space is relied on, it cannot be used to store or process materials, or be built on, apart from guard houses and service structures that don't unduly impede firefighting. Smoke hazard management measures under Part E2, such as smoke detection, smoke and heat vents or smoke exhaust, also apply to large isolated buildings. Where more than one building is on the site, buildings less than 6 m apart are treated as one.
This pathway suits large freestanding distribution buildings on large sites. The unsprinklered option rarely suits smaller lots, because an 18 m clear strip on every side takes too much land. The sprinklered option still needs a continuous 6 m wide fire truck path around the building.
A performance solution
A fire engineer can design a solution that meets the NCC performance requirements by other means. It is assessed by the building certifier, and a fire safety performance solution is referred to Queensland Fire and Rescue for advice.
Fire walls or sprinklers?
Some owners prefer to divide a building with fire walls to avoid sprinklers. Others need one large open floor and accept sprinklers to get it. Both are legitimate. The considerations are:
Capital cost and ongoing cost. A fire wall is a one-off construction cost with little maintenance. A sprinkler system has a capital cost (pipework, and usually tanks and pumps) and an ongoing statutory maintenance cost for the life of the building. In Queensland, the Building Fire Safety Regulation 2008 and Queensland Development Code MP 6.1 require prescribed fire safety installations to be maintained to AS 1851, with records kept and an occupier statement prepared each year. AS 1851 sets monthly, six-monthly, yearly and five-yearly service activities for sprinkler systems, plus longer-interval testing as the system ages.
Flexibility. Fire walls divide the floor and limit how racking and traffic are laid out. Sprinklers keep the floor open but constrain storage heights and layouts to what the system was designed for.
Tenant and insurer requirements. Some logistics tenants and insurers require sprinklers regardless of what the NCC requires.
Storage can trigger sprinklers anyway. This is the point most often missed. Under clause E1D13, sprinklers are required in an "occupancy of excessive hazard" where the fire compartment exceeds 2,000 m2 or 12,000 m3. Excessive hazard includes combustible goods with a total volume over 1,000 m3 stored higher than 4 m. The NCC's list of combustible goods is broad and includes cartons (whatever they contain), paper, textiles, timber, furniture, plastics and rubber. In a Type C building, keeping each compartment within 2,000 m2 and 12,000 m3 keeps it under this trigger, provided the measured area and volume (including any awning space that counts) stay within both limits. In a larger compartment, high racking of ordinary goods can require sprinklers no matter how many fire walls the building has elsewhere.
| Fire walls tend to suit | Sprinklers tend to suit |
|---|---|
| Multi-unit buildings where walls are needed between units anyway | Operations that need one large open floor |
| Owners wanting the lowest ongoing maintenance obligation | Large distribution buildings using the large isolated building provisions |
| Buildings where each compartment can stay within the Table C3D3 limits | High-racked storage of combustible goods in large compartments |
| Owner-occupiers who can work around a dividing wall | Tenants or insurers that require sprinklers |
What fire walls mean in practice
- Operations. Forklift routes and racking must work around the wall. Each opening is a fire door or shutter that must be kept clear to close.
- Future changes. If units might be combined later, plan the opening locations now. Cutting a new opening in a fire wall later means engineering, a new fire door and a building approval.
- Tenant fitouts. Any new penetration through a fire wall must be fire-stopped with a tested system. This is frequently missed in fitout work.
- Titles. In a multi-unit scheme the fire walls should line up with the lot boundaries. See community titles and plan sealing.
Frequently asked questions
What is the maximum fire compartment size for a warehouse?
For Type C construction, 2,000 m2 of floor area and 12,000 m3 of volume. For Type B, 3,500 m2 and 21,000 m3. For Type A, 5,000 m2 and 30,000 m3 (NCC 2022 Table C3D3).
Do multi-unit warehouses need fire walls between units?
In practice, yes. The walls between units are normally built as fire walls so that each unit is its own fire compartment and the building as a whole complies with the size limits.
What fire rating does a warehouse fire wall need?
FRL 90/90/90 in Type C construction and 240/240/240 in Type A or B construction, for Class 7b and 8 buildings.
Can I have a door in a fire wall?
Yes. Doorways can total up to half the length of the wall, and each must be fitted with a self-closing or automatic-closing fire door or shutter.
Do fire walls mean I don't need sprinklers?
Not always. Fire walls can keep a building within the compartment size limits, but storage of combustible goods above 4 m in a compartment larger than 2,000 m2 or 12,000 m3, a tenant requirement or an insurer can still require sprinklers.
What is a large isolated building?
It is a building permitted by NCC clause C3D4 to exceed the normal compartment limits because it has clear open space or sprinklers, and perimeter access for fire trucks.
Sources
- National Construction Code 2022, Volume One: clause C3D3 and Table C3D3; clauses C3D4 and C3D5; clause C3D8; clause C4D6; Specification 5; clause E1D13; Part E2, ncc.abcb.gov.au
- Building Fire Safety Regulation 2008 (Qld); Queensland Development Code MP 6.1, Commissioning and maintenance of fire safety installations
- AS 1851 Routine service of fire protection systems and equipment
- Planning Regulation 2017 (Qld), Schedule 9, Part 3, Division 3 (fire safety referrals)
General information only
This article is general information based on NCC 2022 Volume One, current as at September 2026. It is not design, certification or financial advice. Compartmentation and fire services for your building must be confirmed by your building certifier and, where relevant, a fire engineer.
Planning an industrial warehouse?
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