NCC Fire Resistance Levels (FRL) Explained: What 90/60/30 Means, Type A, B and C Construction, and the FRL Your Wall Needs (2025 Guide)

Every drawing set for a commercial or apartment building carries a string of numbers like 90/60/30 against the walls, and every certifier checks them. This guide explains what those numbers are, where they come from, and how to read the right one off the NCC's tables for the element in front of you. It follows the Code's own order: what an FRL measures, how the building's class and rise in storeys set its Type of construction, and how the Type, the class and the distance to a boundary fix the FRL. The figures are from NCC 2025 Volume One, checked against the published text, and the finder in section 6 reads the Specification 5 tables for you.

In one minute

• An FRL is three numbers in minutes: structural adequacy / integrity / insulation, from the AS 1530.4 furnace test. 90/60/30 means 90 minutes standing, 60 keeping flame out, 30 keeping the far face cool. A dash is no requirement.

• The building's class and rise in storeys set its Type of construction (A, B or C) from Table C2D2. Four or more storeys is always Type A; a single storey is always Type C.

• The Type, the class and the element pick the row in Specification 5, and for an external wall the distance to a boundary or another building picks the column. Structural adequacy is fixed per class (90, 120, 180 or 240); integrity and insulation fall with distance.

• The figures are the same in NCC 2022 and NCC 2025. Only the clause numbers changed, in 2022.

1. What an FRL is

The NCC glossary defines a fire-resistance level, FRL, as the grading periods in minutes, determined in accordance with Specifications 1 and 2 of Volume One, for three criteria: structural adequacy, integrity and insulation, expressed in that order. The three periods come from the Standard Fire Test in AS 1530.4, in which a full-size prototype of the wall, floor, column or beam is loaded, sealed against a furnace and heated on a fixed time and temperature curve while the test watches for three failures.

• Structural adequacy is the ability to maintain stability and adequate loadbearing capacity. A wall that buckles or a floor that collapses at 95 minutes has a structural adequacy of 90.

• Integrity is the ability to resist the passage of flames and hot gases. A crack that lets a cotton pad ignite on the cool side ends the integrity period.

• Insulation is the ability to keep the surface not exposed to the furnace below the temperature limits in AS 1530.4. Once the cool face is hot enough to ignite whatever is stacked against it, the insulation period is over.

A dash means there is no requirement for that criterion. The glossary's own example is 90/–/–: an element that must stay standing for 90 minutes but is not asked to stop fire passing, which is what a column needs. A –/60/60 is the opposite: a non-loadbearing partition that must stop fire and heat for an hour but carries nothing, so its structural adequacy is not tested. And –/–/– means no FRL at all.

How an element earns its FRL is Specification 1. Under S1C2 it can be identical to a prototype tested to AS 1530.4 and reported by an Accredited Testing Laboratory, differ from that prototype only in a minor degree with a report confirming the rating, be designed to the fire sections of the structural standards (AS 3600 for concrete, AS 4100 and AS/NZS 2327 for steel and composite, AS 1720.4 for timber, AS 3700 for masonry), or be one of the tabulated masonry, plaster and concrete constructions in Specification 2. S1C6 adds a rule worth knowing: a non-loadbearing element used where the tables ask for structural adequacy need not meet that criterion, which is why the non-loadbearing tables lead with a dash.

2. The building classes the tables use

Every FRL table in Specification 5 has the same four columns, grouped by fire load and the risk to the people inside. If you can place a building in the right column, half the work is done.

Table column	Classes	What they are (Part A6)
Class 2, 3 or 4 part	2, 3, 4	Apartment buildings (Class 2); hotels, motels, boarding houses, backpackers, workers' quarters and the accommodation part of aged care or a school (Class 3); a single dwelling inside a commercial building, such as a caretaker's flat (Class 4 part)
Class 5, 7a or 9	5, 7a, 9a, 9b, 9c	Offices (Class 5); carparks (Class 7a); hospitals and health-care buildings (9a), assembly buildings such as schools, churches, theatres, sports halls and transport terminals (9b), and residential care buildings (9c)
Class 6	6	Shops, restaurants, cafes, bars, hairdressers, showrooms and other places for the sale of goods or services direct to the public
Class 7b or 8	7b, 8	Warehouses and wholesale storage (7b); factories, laboratories and other buildings where goods are produced, repaired or processed (8)

Houses, townhouses and their sheds are Class 1 and Class 10, which Volume One's Part C does not cover. Their fire separation is in Part 9 of the Housing Provisions, and its one FRL is 60/60/60; our guide to fire-rated walls for houses covers it. The structural adequacy column is the easiest pattern to remember: 90 minutes for residential and hotel classes, 120 for offices, carparks and Class 9, 180 for shops, 240 for warehouses and factories, and that figure stays the same in every Type of construction wherever structural adequacy is required.

3. Rise in storeys sets the Type of construction

Volume One grades fire-resisting construction as Type A, B or C, with Type A the most fire-resisting. C2D2(1) says the minimum Type is determined from Table C2D2, which has only two inputs: the rise in storeys and the class of building.

Rise in storeys is not simply the number of floors. C2D3 defines it as the greatest number of storeys at any part of the external walls, counted above the finished ground next to that part, plus any storeys within the roof space. On a sloping site the count is taken where it is highest. A storey is not counted if it sits at the top and contains only plant, lift equipment or water tanks, or if it is partly below ground and the underside of its ceiling is not more than 1 m above the average finished ground at the external wall (averaged over the lowest 12 m where the wall is longer than that). A mezzanine counts as a storey once it exceeds 200 m² or a third of the room it sits in, whichever is less; and in a Class 7 or 8 building a storey with an average internal height of more than 6 m counts as two, unless it is the only storey above ground.

Three more rules shape the answer. In a building of more than one classification, C2D4 takes the classification of the top storey and applies it to every storey, then reads the most fire-resisting result from the table; a Class 4 caretaker's flat on the top storey is disregarded and the next storey down, or the adjacent part, is used instead. C2D6 lets a two-storey Class 2 or 3 building be Type C rather than B if every sole-occupancy unit has access to at least two exits or its own direct access to a road or open space, and a two-storey sprinklered Class 9c building may do the same within the Table C3D3 compartment size. And C2D5 allows a building to be of mixed Types where a fire wall to C3D8 separates the parts, which is how a Type A tower can stand beside a Type C podium.

4. Fire-source features and distance

For external walls and external columns the tables add a third input: distance from a fire-source feature. The glossary lists them: the far boundary of a road, river, lake or the like adjoining the allotment; a side or rear boundary of the allotment; and an external wall (or the construction edge, where the use is a fire load) of another building on the allotment that is not a Class 10 building. The logic is that a fire can arrive across a side boundary from a neighbour's future building, or from another building on the same site, but not from across a road, so the road's far edge is the datum.

S5C2 decides whether a part of a wall is exposed at all: it is exposed if any horizontal line from it to the feature, or to the feature's vertical projection, is not blocked by another part of the building with an FRL of at least 30/–/– that is neither transparent nor translucent. A part more than 15 m above the top of a neighbouring building's wall is not exposed to it, and neither is a part below finished ground at the boundary. Where a wall runs at an angle to the boundary, S5C2(3) lets you either rate the whole wall for its closest point or rate each part for its own distance, which is why a long wall on a splayed site is often drawn with two FRLs.

5. How the tables are laid out

Once the Type is known, C2D2(2) sends every building element to Specification 5, where each Type has its own set of tables: S5C11a to S5C11g for Type A, S5C21a to S5C21g for Type B and S5C24a to S5C24e for Type C. Within each set the order is the same: loadbearing external walls, non-loadbearing external walls, external columns not in a wall, common walls and fire walls, loadbearing internal walls, non-loadbearing internal walls, and everything else (other loadbearing walls and columns, floors and roofs). The internal wall tables are indexed by what the wall does: bounds a fire-isolated lift or stair shaft, bounds a public corridor or lobby, separates sole-occupancy units, or forms a service shaft.

A few patterns hold across the sets. The external wall FRL falls as the distance grows, and in Type B the loadbearing external wall has five distance bands out to 18 m, where the requirement ends. A fire wall or common wall always carries the full three-criterion FRL of its class in every Type, 90/90/90 in Type C. Floors are 90/90/90 to 240/240/240 in Type A but are not tabulated in Type B or C at all; there the floor rules live in the body of S5C21 and S5C24 and bite mainly on Class 2 and 3 buildings, where a floor between storeys needs 30/30/30, a 60-minute incipient-spread ceiling or a fire-protective covering. Roofs are rated only in Type A, and S5C15 relieves most of those. And a beam or column built into a wall takes the wall's FRL, not its own row, because S5C11(1)(a), S5C21(1)(a) and S5C24(1)(a) all say the element "and any beam or column incorporated in it" must meet the listed value.

6. Find the FRL for your element

Choose the class, the rise in storeys and the element. The section shows the Type of construction, highlights the element and reads its FRL from the right table, with the concessions that commonly apply.

7. Worked examples

Four buildings read through the same three steps. The finder above reproduces each one.

Building	Element	Type	FRL	Where
Three-storey office (Class 5)	Loadbearing external wall 1 m from the side boundary	B	120/120/120	Table S5C21a, less than 1.5 m. At 10 m it drops to 120/30/–; at 18 m to nothing
Four-storey apartments (Class 2)	Wall between two units	A	90/90/90 loadbearing; –/60/60 non-loadbearing	Tables S5C11e and S5C11f. Must run to the floor above or a rated ceiling (S5C11(1)(b))
Single-storey warehouse (Class 7b)	External wall 2 m from the rear boundary	C	60/60/60, tested from the outside	Table S5C24a, 1.5 to 3 m. At 3 m: nothing. Its steel columns need no FRL (S5C6(1))
Two-storey shop with a caretaker's flat above (Class 6 + Class 4 part)	Wall between the flat and the shop's corridor	C	60/60/60	The flat is disregarded for the Type (C2D4(2)) and takes the Class 2 column (C2D7); Table S5C24d

8. Concessions that change the answer

Specification 5 is full of reliefs, and a certifier will expect the drawing to name the one being used. The ones that come up most:

• Steel and timber columns, S5C6(1) and (2). A steel column outside a fire wall needs no FRL in a single-storey building, or in a mostly single-storey building whose two-storey parts are small. A timber column in a single-storey building needs only 30/–/– where the tables ask for an FRL.

• Floors, S5C12. In Type A, a floor laid on the ground, a floor inside a Class 2, 3 or 4 unit, an open-access floor over a rated floor, and a floor over a space that is not a storey and holds no cars, storage or work need no FRL.

• Roofs, S5C15. A Type A roof with a non-combustible covering needs no FRL if the building is sprinklered, has a rise of three or less, is Class 2 or 3, or is under 25 m with a 60-minute ceiling below the roof.

• Timber-framed apartments, S5C20 and S5C23. A Class 2 or 3 building of up to three storeys in Type A, or two in Type B, may be timber framed for its external, common and non-loadbearing fire-resisting walls, and once sprinklered the FRL criteria for its loadbearing walls (and, in Type A, its floors) may drop to 60, with an external wall keeping 90 from the outside.

• Carparks, S5C22 and S5C25. Open-deck and sprinklered carparks in Type B and Type C construction have their own reduced tables.

• Curtain walls, S5C6(4). A non-combustible curtain or panel wall protected throughout by external wall-wetting sprinklers is relieved of the external wall FRL.

Two rules run the other way. S5C3 says that where a rated part depends on another part for support, the supporting part must have at least the structural adequacy of the part it holds up, so a 120-minute wall cannot sit on a 60-minute beam. And S5C11(1)(c) and S5C21(1)(d) restrict loadbearing internal walls and fire walls in Type A and B to concrete, masonry, fire-protected timber or, in Type A, fire-protected steel, each with height and sprinkler conditions.

9. Three things an FRL is not

It is not the same as non-combustible. C2D10 requires external walls and common walls (framing, insulation and facade included), non-loadbearing internal walls that are required to be fire-resisting, and most service shafts in Type A and B construction to be non-combustible regardless of their FRL. A plasterboard external wall can hold 90/90/90 and still fail C2D10 if its framing is timber and no concession applies; a steel column can be non-combustible and have no FRL.

It is not a fire hazard property. Group numbers for wall and ceiling linings, and the smoke and flame indices in C2D11 and Specification 7, describe how a surface burns, not how long an element holds back a fire.

It is not a fire compartment size. The FRL tells you how a wall performs; C3D3 and Table C3D3 tell you how big a fire compartment may be, and C3D8 and C3D9 decide when a wall must be a fire wall in the first place. A drawing needs both.

10. Does NCC 2025 change anything?

No. Table C2D2, the rise-in-storeys rules and every Specification 5 table carry the same values in NCC 2025 as in NCC 2022. The clause numbers changed in 2022, when Specification C1.1 became Specification 5 and its Tables 3, 4 and 5 became the S5C11, S5C21 and S5C24 series, so an older drawing that cites "Spec C1.1 Table 3" is pointing at today's Table S5C11. NCC 2025 applies in Victoria, Tasmania, Western Australia and the ACT from 1 May 2026; New South Wales, Queensland and South Australia stay on NCC 2022 until 1 May 2027; the state adoption guide tracks the dates. Cite the edition in force, and the numbers will be the same.

Check it against the source

The finder above reads the tables; it does not read your site. Whether a wall is exposed to a fire-source feature, whether a mezzanine counts as a storey and whether a concession applies are questions about your building, and AEC Assistant answers them from the full text of NCC 2025 and NCC 2022 for the state you are working in, with the clause cited alongside. Ask it about your project. No credit card.

Sources: NCC 2025 Volume One C2D2 to C2D8, C2D10, C2D11, C3D3, C3D8, C3D9 and Tables C2D2 and C3D3; Specification 1 S1C2, S1C3 and S1C6; Specification 5 S5C2, S5C3, S5C6, S5C11, S5C12, S5C15, S5C20, S5C21, S5C23 and S5C24 and Tables S5C11a to S5C11g, S5C21a to S5C21g and S5C24a to S5C24e; NCC 2025 Glossary (fire-resistance level, structural adequacy, integrity, insulation, fire-source feature, fire wall, common wall, loadbearing, rise in storeys); Part A6 building classifications. Figures verified against the ABCB's published text on 16 September 2026. This article is general guidance; the building surveyor or certifier for your project determines compliance.