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)
An FRL is three numbers in minutes: structural adequacy, integrity and insulation, in that order, from the AS 1530.4 furnace test. Which FRL a wall, column, floor or roof needs comes from the building's class, its rise in storeys (which sets Type A, B or C construction) and, for external walls, its distance from a boundary or another building. This guide explains each step with the clause, and the finder below reads the Specification 5 tables for your element.
Every drawing set for a commercial or apartment building carries a string of numbers like 90/60/30 against the walls. 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. First, what an FRL measures. Next, how the building's class and rise in storeys set its Type of construction. Last, 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. 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. For an external wall, the distance to a boundary or another building picks the column. In Type A, structural adequacy is fixed per class (90, 120, 180 or 240). Integrity and insulation fall with distance.
1. What an FRL is
A fire-resistance level, FRL, is a set of grading periods in minutes for three criteria: structural adequacy, integrity and insulation, expressed in that order. The periods are determined in accordance with Specifications 1 and 2 of Volume One (NCC glossary). They come from the Standard Fire Test in AS 1530.4. In that test a full-size prototype of the wall, floor, column or beam is loaded and sealed against a furnace. It is then 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/–/–. That is 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. It is 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. The element can earn it in any of these ways (S1C2):
It is identical to a prototype tested to AS 1530.4 and reported by an Accredited Testing Laboratory.
It differs from that prototype only in a minor degree, with a report confirming the rating.
It is designed to the fire sections of the structural standards: AS 3600 for concrete, AS 4100 and AS/NZS 2327 for steel and composite, AS/NZS 1720.4 for timber, AS 3700 for masonry.
It is one of the tabulated masonry, concrete, gypsum and protected steel constructions in Specification 1 (Tables S1C2a to S1C2n), built to the rules in Specification 2.
One more rule is worth knowing. A non-loadbearing element used where the tables ask for structural adequacy need not meet that criterion (S1C6). That 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.
How a building is classified, including a mixed building part by part, is set out in our guide to NCC building classes 1 to 10.
| 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. Volume One's Part C does not cover them. Their fire separation is in Part 9 of the Housing Provisions, and its main 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. In Type A it is 90 minutes for residential and hotel classes, 120 for offices, carparks and Class 9, 180 for shops and 240 for warehouses and factories, wherever structural adequacy is required. Type B keeps that pattern, except that some Class 2 and 3 internal walls and columns drop to 60. Type C uses 90 or 60 whatever the class.
3. Rise in storeys sets the Type of construction
Volume One grades fire-resisting construction as Type A, B or C. Type A is the most fire-resisting. The minimum Type is determined from Table C2D2 (C2D2(1)). The table has only two inputs: the rise in storeys and the class of building.
How the rise in storeys is counted on a sloping site, with basements, plant rooms and mezzanines, is worked through in Type A, B and C construction and rise in storeys explained, which has its own calculator.
Rise in storeys is not simply the number of floors. It is 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 (C2D3). On a sloping site the count is taken where it is highest. These rules adjust the count:
A storey is not counted if it sits at the top and contains only plant, lift equipment or water tanks.
A storey is not counted 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. That average is taken 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.
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.
More than one classification. Take the classification of the top storey and apply it to every storey, then read the most fire-resisting result from the table (C2D4). A Class 4 caretaker's flat on the top storey is disregarded. The next storey down, or the adjacent part, is used instead.
Two storeys. A two-storey Class 2 or 3 building may be Type C rather than B (C2D6). The condition is that every sole-occupancy unit has access to at least two exits or its own direct access to a road or open space. A two-storey sprinklered Class 9c building may do the same within the Table C3D3 compartment size.
Mixed Types. A building may be of mixed Types where a fire wall to C3D8 separates the parts (C2D5). That 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
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. It cannot arrive 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. A part is exposed if any horizontal line from it to the feature, or to the feature's vertical projection, is not blocked. The line counts as blocked only 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. Neither is a part below finished ground at the boundary.
Where a wall runs at an angle to the boundary, you may either rate the whole wall for its closest point or rate each part for its own distance (S5C2(3)). That 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, every building element goes to Specification 5 (C2D2(2)). 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. Types A and B follow the same order:
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
everything else (other loadbearing walls and columns, floors and roofs).
Type C has five tables: external walls, external columns, common walls and fire walls, internal walls, and the roof.
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
forms a service shaft.
A few patterns hold across the sets:
The external wall FRL falls as the distance grows. 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. In Type C that is 90/90/90.
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. They bite mainly on Class 2 and 3 buildings, where a floor between storeys needs 30/30/30 or a fire-protective covering, or in Type B a ceiling with a 60-minute resistance to the incipient spread of fire (S5C21(1)(f) and S5C24(1)(e)).
Roofs are rated only in Type A, and most of those are relieved (S5C15).
A beam or column built into a wall takes the wall's FRL, not its own row. The clauses all say the element "and any beam or column incorporated in it" must meet the listed value (S5C11(1)(a), S5C21(1)(a) and S5C24(1)(a)).
6. Find the FRL for your element
Choose the class, the rise in storeys and the element. The section shows the Type of construction and highlights the element. It reads the element's 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. 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 needs no FRL. Nor does a floor inside a Class 2, 3 or 4 unit, or an open-access floor over a rated floor. Nor does a floor over a space that is not a storey and holds no cars, storage or work.
Roofs, S5C15. A Type A roof with a non-combustible covering needs no FRL if the building is sprinklered or has a rise of three or less. The same applies if the building 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. Once it is sprinklered, the FRL criteria for its loadbearing walls (and, in Type A, its floors) may drop to 60. An external wall keeps 90 from the outside.
An apartment building's own carpark, S5C9. In a building of only Class 2 and Class 7 parts and no more than four storeys, a single Class 7 part that sits wholly within one storey and serves the building, such as its carpark, may take the Class 2 FRLs. The same applies with Class 3 in a building of no more than three storeys.
Carparks, S5C19, S5C22 and S5C25. A carpark may use its own shorter list of FRLs instead of the tables: S5C19 in Type A, S5C22 in Type B and S5C25 in Type C. It qualifies if it is sprinklered to Specification 17 or is an open-deck carpark. In Type A and B, an open-deck carpark qualifies only as a separate building; one that is part of a larger building must be sprinklered and meet the separation conditions in the clause.
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. 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 (S5C3). So a 120-minute wall cannot sit on a 60-minute beam. And loadbearing internal walls and fire walls in Type A and B are restricted to concrete, masonry, fire-protected timber or, in Type A, fire-protected steel (S5C11(1)(c) and S5C21(1)(d)). Each comes with height and sprinkler conditions.
9. Three things an FRL is not
It is not the same as non-combustible. In Type A and B construction, these must be non-combustible regardless of their FRL (C2D10):
external walls and common walls (framing, insulation and facade included)
non-loadbearing internal walls that are required to be fire-resisting
most service shafts.
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 describe how a surface burns, not how long an element holds back a fire. So do the smoke and flame indices in C2D11 and Specification 7.
It is not a fire compartment size. The FRL tells you how a wall performs. How big a fire compartment may be is a separate question (C3D3 and Table C3D3). So is when a wall must be a fire wall in the first place (C3D8 and C3D9). A drawing needs both.
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. AEC Assistant answers them from the full text of NCC 2025, 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, S5C9, S5C11, S5C12, S5C15, S5C19 to S5C25 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 NCC 2025 text on 16 September 2026 and checked again on 28 September 2026. This article is general guidance; the building surveyor or certifier for your project determines compliance.
Questions this guide answers
What does FRL mean in the NCC?
Fire-resistance level: the grading periods in minutes, determined under Specifications 1 and 2 of NCC Volume One, for structural adequacy, integrity and insulation, written in that order. A dash means there is no requirement for that criterion, so 90/–/– requires 90 minutes of structural adequacy only, and –/–/– requires no FRL at all.
What do the three numbers in an FRL like 120/90/60 mean?
Structural adequacy is the ability to stay standing and carry its load under the AS 1530.4 fire test; integrity is the ability to keep flames and hot gases from passing through; insulation is the ability to keep the unexposed face below the temperature limits in AS 1530.4. So 120/90/60 means 120 minutes of stability, 90 of integrity and 60 of insulation.
What is Type A, B and C construction?
The three levels of fire-resisting construction in NCC Volume One, Type A the most fire-resisting. Table C2D2 assigns the Type from the rise in storeys and the building class: four or more storeys is always Type A; three storeys is Type A for Class 2, 3 and 9 and Type B for Class 5 to 8; two storeys is Type B for Class 2, 3 and 9 and Type C for Class 5 to 8; one storey is Type C for every class.
What FRL does an external wall need?
It depends on the Type of construction, the class of building, whether the wall is loadbearing and its distance from a fire-source feature. In Type A a loadbearing external wall less than 1.5 m from the feature needs 90/90/90 for Class 2 or 3, 120/120/120 for Class 5, 7a or 9, 180/180/180 for Class 6 and 240/240/240 for Class 7b or 8 (Table S5C11a); in Type C the same wall needs 90/90/90 within 1.5 m, 60/60/60 (or nothing for Class 2 and 3) from 1.5 to 3 m and nothing beyond 3 m (Table S5C24a).
What is a fire-source feature?
The far boundary of a road, river, lake or the like adjoining the allotment; a side or rear boundary of the allotment; an external wall of another building on the allotment that is not a Class 10 building; or the construction edge or perimeter of another building on the allotment that is not a Class 10 building and has a use that constitutes a fire load. Distances in the external wall tables are measured to the nearest of these.
