C/AS1 Protection from Fire

No classified use set in the project. Set it once and this page knows whether the building is risk group SH, which is all C/AS1 covers.

Building type

Other uses

C/AS2 exclusions

Sprinkler system

All three extend travel distances and remove the external wall FRR. Only NZS 4515 / 4541 unlock the exemptions for roofs, cladding, external safe paths and the fire appliance hard-standing.

1. Sprinklers

   Not selected

   C/AS1 never mandates sprinklers. Installing them raises DEOP/TOP to 40/100 m and removes the external wall FRR; NZS 4515/4541 also remove the roof, cladding, external safe path and hard-standing distance requirements.

   3.3.1.1, 5.1.1.1

2. Firecell floor area

   No limit

   2.1.1.1

Measured distances

Start within 1.0 m of the most remote point; measure orthogonally 1.0 m from walls if furniture positions are unknown; stairs count as plan length plus landings; ladders count as vertical height (3.3.2.1).

Once outside the building

Room occupant load

1. Dead end open path

   12000 mm (12 m) ≤ 35000 mm (35 m)

   Column used: Household unit + Type 1. A single escape route is permitted (3.1.2.1).

   Table 3.3.1.1

2. Total open path

   18000 mm (18 m) ≤ 75000 mm (75 m)

   Table 3.3.1.1

3. External safe path

   Not required

   There is more than one direction of escape once outside, so no external safe path is needed.

   3.3.5.1

Ancillary spaces

Wall or ceiling systems

1. Within the unit

   Not required

   A single household unit is one firecell; its internal floors and partitions need no FRR.

   Appendix B

2. Interior surface finishes

   No requirement

   Without foamed plastics or combustible insulation there are no surface finish requirements in SH.

   4.2.1.1

What is on the other side

If the other property is a road, railway or public open space, the relevant boundary is the far side of it (Appendix B).

Eaves

Other situations

1. External wall

   FRR 30/30/30 required, both directions

   Less than 1 m from the relevant boundary. The wall must resist fire from both directions; any unrated window or door is an unprotected area (Appendix B), so openings within 1 m must be rated or removed.

   5.1.1.2(a)

2. Eaves

   FRR 30/30/30 required

   Where the external wall needs an FRR, the eaves projection must be 30/30/30 or the wall extended to the roof underside.

   5.2.1.1

3. Cladding materials

   Non-combustible, limited combustible or Type A

   Less than 1 m from the relevant boundary, regardless of height.

   Table 5.3.1.1, BPS 8.4.1

Site conditions

1. Fire appliance access

   N/A

   Part 6 applies to multi-unit buildings only.

   6.1.1.1

Appliances

1. Heating appliances

   Not selected

   Without a fireplace or combustion appliance, Part 7 reduces to 7.2: electrical installations to G9.

   7.2.1.1

1. Smoke alarms Type 1 required

   2.2.1.2, C.2.1, NZS 4514:2021

2. Where the smoke alarms go Per NZS 4514:2021 §2.2, show them on the plans

   • Every bedroom and every living space, and each hallway and landing (2.2.1 b)
   • At least one on every level of a multi-level household unit (2.2.1 d)
   • Where doors close the kitchen off from the hallways and living spaces: an alarm in the kitchen that its manufacturer says suits a kitchen, and a heat alarm will do (2.2.1 c)
   • Where more than one is needed: all interconnected, so one activating sounds them all (2.2.1 e)
   • No wall further than 5 m from an alarm, and alarms within 10 m of each other in any direction (2.2.2)
   • On or near the ceiling; at least 200 mm from the wall on a flat ceiling or one sloping less than 1 in 10 (2.2.3 a)
   • On a ceiling steeper than 1 in 10: on the high side, 200–500 mm from the apex (2.2.3 b)
   • Wall-mounted only where a ceiling mount is not possible: top 100–300 mm from the ceiling (2.2.3 c)
   • With exposed beams, rafters, purlins or joists: at least 200 mm clear of the member, and Table 1 decides between the member’s underside and the ceiling by its depth and spacing (2.2.5)

   2.2.1.2, NZS 4514:2021 §2.2

3. Default FRR 30 / 30

   2.3.1.1, 2.3.1.2, BPS 8.2

1. Escape route dimensions D1/AS1 plus the following

   • Door openings at least 1955 mm (1.955 m) clear height (3.2.1.1(b))
   • Widths: 700 mm horizontal, 850 mm vertical, 1000 mm (1 m) for an external safe path (3.2.2.1)
   • Doors at least 600 mm clear opening, no leaf under 500 mm in multi-leaf doors, opening at least 90°, and the swing must not obstruct the required width (3.2.4.1)
   • Handrails and door assemblies may project no more than 100 mm (3.2.3.1)
   • Locks: no key operation in the direction of escape; a key one side and a turn knob the other is acceptable (3.2.4.2)

   3.2

1. Default FRR Unless stated otherwise, life and property ratings are both 30 minutes (2.3.1.1); FRRs are determined per Building Product Specifications Section 8.2 (2.3.1.2). Cladding must be specified to BPS 8.4.1 regardless of distance (5.3.1.1(a)).

   2.3.1.1

2. Windows in a wall that needs the FRR More than 1000 mm (1 m) from the boundary: not fire rated

   5.1.1.2

Risk group SHC/AS1 Table 1.1.1.1

Detached household units; low-rise multi-unit dwellings where every unit has its own escape route (side-by-side townhouses, or two stacked units with the upper floor at an escape height under 4.0 m); boarding houses, homestays and B&Bs with fewer than 6 paying guests; outbuildings. Apartments, three or more stacked units and buildings with shared stairs are SM and go to C/AS2.

Risk group SM and SIC/AS2 Table 1.1.1.1

The two groups a design lands in once it leaves C/AS1. SM is sleeping use where the occupants can be expected to evacuate themselves: apartments, three or more stacked units, hotels, motels, backpackers, serviced apartments. SI is care and detention: hospitals, aged care, hospices, sedated day treatment, detention. The split is not nominal: E.2.2.1 gives each group its own unprotected area table (SM reads E.2.2.1A, SI reads E.2.2.1B), and the largest single opening and fire resisting glazing tables have their own columns too. The C/AS2 tool reads each group's own tables.

Household unitC/AS1 Appendix B

A building or part of a building used as the home of a single household. Hostels, boarding houses and other specialised accommodation are excluded.

Relevant boundaryC/AS1 & C/AS2 Appendix B

The boundary between your allotment and other property from which external wall distances are measured. Where the other property is a road, railway or public open space, it is the far side of that space.

Notional boundaryC/AS1 5.1.2.1 · C/AS2 5.2.1.8

A boundary assumed for fire purposes between two buildings on the same property under a single land title, used in place of the relevant boundary. It may not sit closer than 1.0 m to any unprotected area in the external wall receiving the radiation, and only where the walls are at less than 90°. C/AS1 uses it between two household units under one owner (5.1.2.1); C/AS2 puts it more widely: between the external walls of firecells in the same building, or of separate buildings on the same property (5.2.1.8), which is the case when two units of one apartment building face each other.

Firecell and fire separationC/AS1 & C/AS2 Appendix B

A firecell is any space, or group of contiguous spaces on the same or different levels, enclosed by any combination of fire separations, external walls, roofs and floors. A fire separation is the building element that separates one firecell from another, or a firecell from a safe path, and carries a specified FRR. Under C/AS1: two storeys of one unit are a single firecell and the floor between them is not rated, while a floor between different units is a fire separation and needs 30/30/30.

Unprotected areaC/AS1 & C/AS2 Appendix B

Any part of an external wall that is not fire rated or has less than the required FRR, plus any part with combustible material more than 1.0 mm thick attached or applied to its outer face, whether as cladding or for any other purpose. Non-fire-rated windows, doors and openings all count, and C/AS2 spells out that non-fire-rated external wall construction does too. The two documents define it identically.

FRR 30/30/30C/AS1 & C/AS2 Appendix B

The three numbers are the minutes achieved for structural adequacy, integrity and insulation, always in that order. Under C/AS1, unless it says otherwise, both the life rating and the property rating are 30 minutes. C/AS2 reads Table 2.3.1.1 instead, by risk group and by whether the firecell is sprinklered: risk group SM is 60 minutes unsprinklered and 30 sprinklered.

Life rating and property ratingC/AS2 Table 2.3.1.1

The two columns of Table 2.3.1.1. The property rating is the FRR applied to construction so that it protects other property; the life rating is the other column, and protects people. Which one applies is named by the paragraph: 4.1.1.1 picks by ownership (life where firecells are under common ownership, property where they are not or a property boundary runs between them), 5.2.2.2 names the property rating, 5.2.2.4 names the life rating. For risk group SM the two columns hold the same minutes (60 unsprinklered, 30 sprinklered), so nothing separates them in a building that is SM throughout. They do part for CA, WB and WS, and 4.1.1.2 separates adjoining firecells by the higher of the two.

Escape heightC/AS1 & C/AS2 Appendix B

The vertical distance between the floor level of the firecell being considered and the floor level of the final exit, taking the greatest value. Within a multi-storey unit it is measured from the floor furthest from the exit. For stacked units it is how far the upper unit's floor sits above the ground-level exit.

Building heightC/AS1 & C/AS2 Appendix B

The vertical distance between the floor level of the lowest occupied space above the ground and the top of the highest occupied floor, excluding rooftop stair, lift and plant enclosures. A single-level building's is therefore zero, which is why the multi-level in 5.5.1.4 and 5.5.2 is not a second condition but a consequence of the definition. C/AS1 uses it only in cladding Table 5.3.1.1. C/AS2 uses it for cladding (5.5.1.4 at 10 m or more, 5.5.2 at 25 m or more) and in 2.3.2.7 (b) at more than 10 m, which is a different threshold from 5.5.1.4's, not the same one.

Non-combustible, limited combustible, Type A, Type BBPS 8.1.1 & 8.4.1

The four grades of external cladding material, all defined in the BPS and only referred to by C/AS2. Non-combustible and limited combustible are settled by the combustibility methods in BPS 8.1.1. Type A and Type B come from a cone calorimeter test (ISO 5660-1 or AS/NZS 3837) measuring peak heat release and total heat against BPS Table 8.4.1.2, with Type A the stricter of the two. Strictest first: non-combustible, limited combustible, Type A, Type B. Type B is reachable only by risk group SI (5.5.1.3), so no SM wall gets there. BPS 8.4.2 is a different thing again: the whole cladding system rather than a material, which is the route a building of 25 m or more takes.

Group NumberBPS 8.5

The fire performance classification of wall and ceiling lining materials, determined under BPS Section 8.5. C/AS1 only requires a completed system of 3 or less where foamed plastics or combustible insulation are used.

Open path, dead end, safe path, final exitC/AS1 & C/AS2 Appendix B

An exitway is all of an escape route protected by fire or smoke separations, or by distance when exposed to open air, terminating at a final exit. An open path is the part within a firecell where occupants may be exposed to fire or smoke; a dead end is an open path with only one direction of travel; a safe path is the part of an exitway protected by fire separations, external walls, or by distance in open air; the final exit is the point of entry to a safe place, which may be beyond the building's exit door. C/AS2 adds one thing: 5.2.2.2 lets a safe path's external wall be 100% unprotected, at the price of the property rating on the walls between the safe path and the adjacent firecells.

External safe pathC/AS1 3.5.3

The outdoor section between the building exit and the final exit that must be protected when there is only one direction of escape. Minimum width 1.0 m, protected by distance, fire rated construction or sprinklers in the adjacent firecells.

Type 1 smoke alarm systemC/AS1 2.2.1.2 · NZS 4514:2021

Interconnected domestic smoke alarms to NZS 4514:2021, required in every household unit. No connection to a remote receiving centre is needed.

Building Product Specifications (BPS)MBIE, Building Act 2004 s 25B

A separate MBIE document, issued under section 25B of the Building Act 2004, holding the standards, test methods and specifications for building products. Its First Edition was published on the same day as C/AS1 Second Edition Amendment 1, 28 July 2025, which is what let C/AS1 move its Appendix E fire test methods across, drop its direct references to NZS/BS 476, AS/NZS 3837 and the rest, and refer out instead at Paragraphs 2.3.1.2, 4.2.2.1 and 5.3.1.1. It is amended on its own schedule after that: Amendment 1, effective 2 April 2026, added specifications for wall bracing elements and for fire doors and fire resisting glazing. So its edition has to be confirmed separately from C/AS1's; and C/AS1 1.2.5.2 says it cannot be used in isolation to demonstrate compliance.

Smoke alarms2.2.1.2, C.2.1, NZS 4514:2021

Every household unit needs at least an interconnected smoke alarm system to NZS 4514:2021. Connection to a remote receiving centre is not required.

Where the smoke alarms go2.2.1.2, NZS 4514:2021 §2.2

C/AS1 asks only for a Type 1 system per household unit; where the alarms go is NZS 4514’s. That is deliberate rather than an omission: F7/AS1 Fifth Edition records that the domestic smoke alarm requirements were removed from it because C/AS1 and C/AS2 now reference the standard, so no MBIE document carries them. What §2.2 requires is below in our own words; read the standard itself for the detail.

Where not to put a smoke alarmNZS 4514:2021 §2.2.6

Advised against by NZS 4514:2021 §2.2.6 (“should not”) 2.2.6 is written as “should not” rather than “shall”, so this is advice and not a requirement. It is worth following anyway: what it avoids is nuisance alarms and dead detection, and both end with the occupant taking the alarm down.

• Dead air spaces
• Within 300 mm of a light fitting
• Within 400 mm of any air-supply opening, air-conditioning or forced-air supply, or outside the circumference of a ceiling fan’s blades
• Within 1 m of a cooktop, and keep 3 m where the room allows it
• Attics, roof spaces, and anywhere with extremes of temperature, dust or high airflow
• A surface that runs much hotter or colder than the room around it: a ceiling under an unfinished roof space, say, or an outside wall with no insulation

Default FRR2.3.1.1, 2.3.1.2, BPS 8.2

Unless stated otherwise, the life rating is 30 minutes and the property rating 30 minutes, determined per BPS Section 8.2.

Windows in a wall that needs the FRR5.1.1.2

A wall needing 30/30/30 does not make every window in it need one. 5.1.1.2 adds, after a) and b), that windows more than 1 m from the relevant boundary in a household unit wall requiring the FRR do not need to be fire rated. The wall still does, and the exemption is only usable if the drawings dimension where the windows are.

Cladding finished face to the boundaryAppendix B, 5.1.1.2, 5.2.1.2

Show this dimension on the drawings C/AS1 measures to the external wall, and Appendix B defines that as any exterior face of the building: once built, the finished face of the cladding, not the framing and not the structural grid. Every threshold in Part 5 is read from that face: 1000 mm (1 m) for a household unit, 5000 mm (5 m) for stacked units, 650 mm from the eaves edge. Showing the dimension is a drawing convention rather than a paragraph of C/AS1, but nothing in Part 5 can be checked without it.

Which line is the boundaryAppendix B

For a road, railway line or public open space, measure to the far side of it Appendix B makes the relevant boundary the nearest boundary of the other property, except that where the other property is a road, railway line or public open space, the relevant boundary is the one on the far side of it. A street elevation measured to the kerb is measured to the wrong line, and measured short, so the tool will ask for an FRR the design does not need. The definition sets out similar exceptions for cross-lease, company lease, licence and unit-plan common open space; read it rather than this summary.

Where a roof becomes a wallH1/AS1 Definitions, roof; E2/AS1 Definitions, roof and external wall; E2/AS1 1.1.1.1 c); C/AS1 and C/AS2 Definitions, external wall

H1/AS1 and E2/AS1 define a roof the same way: a surface at 60° or less to the horizontal. C/AS1 and C/AS2 come at the same line from the other side, defining an external wall as any exterior face within 30° of vertical, and say that this includes a roof. Both definitions take in 60° itself, so a face pitched at exactly 60° is a roof for energy efficiency and weathertightness and an external wall for fire. Steeper than 60°, it is not a roof to H1/AS1, and C treats it as an external wall. E2/AS1 goes further than a definition: its scope is limited to buildings whose external walls are vertical and whose roofs are 60° or less (1.1.1.1 c)), so a building with any face between 60° and vertical, a mansard for one, is outside E2/AS1 altogether, and its weathertightness has to be shown some other way, such as an alternative solution.