Protection from Fire

Frequently asked questions

Since publication on 10 April 2012, the Acceptable Solutions and the Verification Method for Protection from Fire (C/AS1-C/AS7 and C/VM2) have been subject to an ongoing process of continuing improvement. Many of the improvements have been and will be informed by feedback and requests for clarification.

The FAQs are split into the following sections:

If a building complies with an Acceptable Solution or Verification Method for Protection from Fire as adjusted by the interpretations listed on this site, it is also deemed to comply with the Building Code. It therefore does not need further specific engineering design.

The intent is that the interpretations produced here may be incorporated in the next amendment of the Acceptable Solutions, Verification Method, and commentaries as required.

If you can't find the answer to your question here, you can use our 'Ask a question' form.

1. Acceptable Solutions C/AS1 – C/AS7 interpretations

In this section

1.1 Are there any exceptions to the requirements of the Acceptable Solutions to extend an alarm or sprinkler system throughout a building?

The Acceptable Solutions for Protection from Fire require a fire alarm system and fire sprinkler system to be extended throughout a building, if a system is required in any part of the building.

However, the following exception applies where a single-storey building is separated at the ground floor into two or more unit titles, with fire separations (designed with the relevant property rating) between each unit.

Figure 7.1 Single Storey Commercial Building

Figure 7.1

Title 1 has a fire sprinkler system installed, Titles 2 and 3 may be unsprinklered (provided there is no other requirement to install a system in those titles). They are effectively treated as separate buildings.

This does not apply in a multi-storey building where the floors are unit title separations/boundaries.

Notes: C/AS7 also allows for sprinkler protection of the car park firecell to not be extended throughout a building when the criteria of C/AS7 2.2.3 have been met.

The Acceptable Solutions for Protection from Fire allow a heat detection system to be installed in certain areas in lieu of a smoke detection system .

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1.2 Why was the following consultation text in 3.11.1 not adopted?

“If an escape route enters a space exposed to the open air (e.g. an open stairway, a balcony, across a roof or a ground level path), it shall meet the requirements of a safe path between that point and the final exit unless the final exit can be reached within the dead end open path or total open path distance, whichever applies, including the travel distance along the external escape route".

It is recognised for many layouts, the above wording results in a safe building.

Example: In single fire cell buildings where the external escape route is subject only to radiation from that fire cell, and the travel distance to a place of safety is within the dead end open path travel distances for the building, occupants can escape safely.

However there were other configurations of external escape route that the consultation 3.11.1 text did not address, for example:

a) The risk in a row of shop units where each unit is a fire cell with an independent alarm. Here an external escape route that passes each unit would need protection even if it was within open path travel distance limitations.

b) The risk in an apartment building where there is a choice of external escape route but both pass different parts of another firecell containing the fire.

The original wording is retained, however we will continue to explore different layout permutations and further information will be provided as it is developed.

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1.3 Figure 5.2 is different in C/AS3 than the other acceptable solutions? Do adjoining fire cells still have to comply?

Yes, while the diagram in C/AS3 specifically reflects adjoining buildings, it is also applicable to adjoining fire cells (in the same way as the other C/ASs).

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1.4 What is meant by “open path lengths from any point on the floor to no fewer than 2 exits” in 3.4.2 d)

The total open path length shall be the maximum distance possible a point on the floor to the second nearest exit.  In other words; the open path length shall be determined based on the assumption that the nearest exit is blocked and be taken as the maximum length possible from a point on the floor to the next closest exit.  This can include a section of dead end open path as in Figure 3.8.

If there are fixed furnishings then the travel distance to the next closet exit shall be measured around the furnishings; if there are no fixed furnishings or their position is unknown then the travel distance shall be measured around the floor’s perimeter all as shown in Figures 3.7(a) and (b).

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1.5 Does Paragraph 5.3 of C/AS1 mean fire spread from a lower roof does not need to be considered, because the building is not attached even if the gap is small?

To be considered not attached for the purposes of this clause, the external wall must be at least 1m from an adjacent wall and 0.65m from an adjacent eave?

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1.6 Are unrated portions of façade smaller than 0.1m2 permissible in C/AS1 designs?

Yes, it is permissible to have unrated portions of façade smaller than 0.1m2 provided they comply with Figure 5.1 and paragraph 5.4 of acceptable solution C/AS2.

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1.7 What is meant by Capable Height of Storage?

The term capable of storage is included to capture possible future uses of warehousing to prevent future upgrades due to a change of use. A designer of storage buildings should consider the possible future uses and design for flexibility in use.

Capable height of storage is the maximum height to which storage is possible within a particular building accounting for all relevant factors including, but not limited to, the materials stored, clearances needed to move materials around and floor loadings. For maximum future versatility the capable height of storage can be 1m below the height to the apex.

However where the fire safety systems in the building are designed for a particular maximum storage height, and it is possible that height may be exceeded, signs shall be provided advising of the maximum storage height.  Those signs shall be provided in sufficient number, be clearly visible and readily understandable, and be maintained in good condition.

Note that outbuildings and do not need to be addressed for height of storage. An outbuilding is any building not intended for human habitation and accessory to the principal use of associated buildings. Outbuildings can include certain, essentially unoccupied, farm buildings such as hay barns, bunkers and machinery shelter.  Buildings that people work in or otherwise occupy for long periods during the day and which contain amenities and services cannot be considered as Risk Group SH.

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1.8 What is meant by “open path lengths from any point on the floor to no fewer than 2 exits” in 3.4.2 d)

The total open path length shall be the maximum distance possible a point on the floor to the second nearest exit.  In other words; the open path length shall be determined based on the assumption that the nearest exit is blocked and be taken as the maximum length possible from a point on the floor to the next closest exit.  This can include a section of dead end open path as in Figure 3.8.

If there are fixed furnishings then the travel distance to the next closet exit shall be measured around the furnishings; if there are no fixed furnishings or their position is unknown then the travel distance shall be measured around the floor’s perimeter all as shown in Figures 3.7(a) and (b).

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1.9 Where there are more than one risk group in a firecell what constitutes the primary risk group?

The primary risk group is the worse-case activity within the firecell. The activity however can have other supplementary activities in support of the primary risk group.  For an example a shop unit the primary risk group is the retail space (Risk Group CA) however there are other activities in support such as administration offices (Risk Group WB) and low level storage rooms (Risk Group WB). The primary purpose of the shop is a retail space and therefore the primary risk group is Risk Group CA with other risk groups are ancillary to the primary risk group. Ancillary risk groups must provide direct support and be integral to the main activity of the firecell.

An exemption is where the other activity includes high level storage (Risk Group WS), vehicle parking (Risk Group VP) or sleeping uses (Risk Group SH, SR) where these areas should be separate firecell otherwise the worse-case risk group governs the primary risk group.

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1.10 What is the intent of Paragraph 5.1.2 of C/AS1 Notional boundary – firecells on the same property?

Paragraph 5.1.2 requires boundary check between buildings of Risk Group SH that are on the same property title.

The intention of the requirement for fire separation in this paragraph is to protect buildings with a sleeping risk. For example should a fire occur in an unoccupied outbuilding that is close proximity to a house this could threaten the life safety of the sleeping occupants.

Paragraph 5.1.1 requires all walls within 1m of a boundary to be fire rated for 30/30/30 FR. For buildings on the same property a notional boundary would need to be 1m from both buildings i.e. 2m apart to not require fire rating.  In the situation where  external walls of two buildings are within 2m of each other, and at least one building has a sleeping use, at least one external walls that face each other is required to be fire rated.

This does not apply where the two buildings which are within 2m of each other are outbuilding and on the same property as there is no threat to sleeping risk or other property.

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1.11 Ask a question

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2. Verification Method C/VM2 interpretations

In this section:

2.1 Where a challenging fire is placed in the main entrance lobby of a building is it appropriate to consider the occupants evacuating through the balance of the exits for this ASET vs. RSET?

Yes, noting that for the other challenging fire scenarios in this building 50% of the occupants should be considered as evacuating via the main entrance for the ASET vs. RSET analysis.

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2.2 Why doesn’t Table 3.3 (Pre-travel activity times) in C/VM2 give a time for a voice alarm signal for spaces in which the occupants are sleeping and familiar with the building?

The table reflects the current requirements in NZS 4512 and acceptable solution F7/AS1 for alarm systems that alert occupants who are sleeping and familiar with the building. Voice alarms are not required in these spaces.

Should a voice warning sound be used in lieu of the tonal sound, then the pre-travel time should be as per the tonal time (this reflects that the critical factor in a residential setting pre-travel activity time is the time to awake.

For more information:

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2.3 Are the modifications to NZS 4541:2013 listed in Appendix B of the Acceptable Solutions applicable to Verification Method C/VM2 designs?

Yes, it is the intention that for compliance with the Building Code the parts of the sprinkler standard amended by Appendix B stand for all methods of compliance.

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2.4 When designing an apartment building can an engineer use the Property Rating specified in the Acceptable Solutions for Protection from Fire as a default inter-tenancy rating rather than calculate the burn out time of the spaces?

The Acceptable Solutions are intended to provide a conservative solution for the design of buildings. The fire resistance rating of inter-tenancy walls is dependent on the fire load, thermal properties, and ventilation of the fire compartment. Given the conservative basis of the Property Rating it would be expected that any calculated burn out time would, in most cases, be equal to or less than the rating required by the Acceptable Solution.

Therefore it is permitted to use the Property Rating of the Acceptable Solutions to determine the FRR of the inter-tenancy walls in an apartment building.

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2.5 What does the text “Where occupants in the rest of the building use escape routes protected from the effects of fire (such as exit-ways), the effect of sprinklers to control the fire (with constant HRR) shall be ignored for assessing the performance required of the construction protecting the escape route” in the CF Scenario mean?

It means do not use a sprinkler controlled heat release rate if you are doing modelling to demonstrate that the barrier will remain effective in protecting the escape route. The effect of sprinklers is already accounted for by halving the fire load energy density as described in Table 2.3. This also which equates to a 50% concession if applying equation 2.1 in section 2.4.4.

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2.6 Can any of the design inputs into C/VM2 be varied?

The Verification Method C/VM2 method is a complete design system with interrelated inputs and design parameters that result in an acceptable level of risk. Therefore it is not appropriate to vary the inputs and design parameters when using the C/VM2 method.

C/VM2 inputs cannot be replaced with elements from Acceptable Solutions C/ASx or specific design. Using other inputs can have significant effect on the outcome.

Should a designer wish to vary the design inputs other than listed in C/VM2 the design is an Alternative Solution and all design inputs must be justified.

However where the design input is not described in C/VM2 (eg. Boilers) the designer shall present a suitable input at the FEB stage and justify that it is appropriate for the project to be tested by the reviewer & NZFS. This is still within the framework of the Verification Method.

When using fire engineering design methodologies, designers are expected to exercise care and intelligent application of those design methodologies. The Verification Method is suitable for use by professional fire engineers who are proficient in the use of fire engineering modelling methods and who can apply appropriate judgement to the model inputs and results.

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2.7 What is intent of Block Exit (BE) Design Scenario?

The construct of this scenario has three requirements:

  1. Any escape route (open path) that serves more than 50 people requires a second exit.
  2. This scenario limits single escape stair to a maximum capacity of 150 people non-sprinklered or 250 people sprinkler protection. If there are more than one stair than this restriction does not apply. For buildings where one stair is a single means of escape from some floors but not others then stair shall be designed such that the maximum capacity is not exceeded.
  3. The travel distance shall be limited along the escape route to reach the stair (i.e. open path). There is no requirement within C/VM2 to design for fires within the vertical stair enclosures (i.e. safe path) or limit travel distance in protected enclosures.

There is no fire engineering analysis required for this design scenario.

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2.8 Which areas need visibility monitored for when the occupancy exceeds 1000 people in the firecell (C4.4)?

Clause C4.4 states that “Clause C4.3(b) and (c) do not apply where it is not possible to expose more than 1000 occupants in a firecell protected with an automatic fire sprinkler system.”

This clause is intended to provide an additional level of safety for buildings where a large occupancy can be exposed to the adverse effects of a fire environment. However when carrying out a fire analysis the area in the immediate vicinity of the fire does not need to be assessed for visibility or FEDthermal and only areas remote from the fire where over 1000 people will be affected will be required to be assessed for all tenability criterion.

For the purposes of identifying what areas are considered in the immediate vicinity or remote from the fire, the following would apply:

  • In an atrium, where sprinklers are provided, if the floor of fire origin has less than 1000 people then that floor does not need to be assessed for visibility and FEDthermal, however all other floors above or below require visibility, FEDco, and FEDthermal assessment.
  • In a large area of the same level such as a sprinkler protected shopping centre, ballroom, arena, or conference room for example, the region immediately surrounding the fire origin that has less than 1000 occupants (determined by the occupant density) does not need assessment for visibility and FEDthermal however areas outside of this area require assessment.
  • Other situations not described by the above should be discussed and agreed with FEB stakeholders during the FEB process.

This is what is meant by ‘it is not possible to expose more than 1000 occupants’.

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2.9 When does the additional robustness check of vertical escape routes apply?

Design Scenario RS only applies to buildings where the occupancy exceeds: 150 people, or 50 people in a sleeping occupancy where the occupants are neither detained or undergoing some treatment or care, or 20 people detained or undergoing treatment or care or children in early childhood centres. If these occupancies are not exceeded the whole design scenario does not apply.

The additional robustness check for sprinklered sleeping occupancies only applies when the above occupancies are exceeded. This is an additional check for visibility in the stairwell due to the higher risk of an occupancy exposed in a single escape route and vertical escape route served by more than 250 people.

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2.10 For Horizontal Fire Spread design can a radiant heat flux be used for storage occupancies?

Design Scenario for Horizontal Fire Spread provides Design Fire for various occupancies apart from storage use. For storage buildings the following emitted radiant heat flux can be used for sprinklered and non-sprinklered occupancies:

FLED Emitted Radiant Heat Flux From Unprotected Areas
  Without Sprinklers With Sprinklers

<400 MJ/m2

83 kW/m2

58 kW/m2

400 – 800 MJ/m2

103 kW/m2

72 kW/m2

>800 MJ/m2

144 kW/m2

101 kW/m2

Emissivity of fire gases shall be taken as 1.0.

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2.11 Ask a question

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3.0 Procedural issues

In this section:

3.1 Is there any guidance on assessing ‘means of escape from fire’ for alterations to existing buildings?

The Ministry of Business, Innovation and Employment (MBIE) has developed “Guidance: Requesting information about means of escape from fire for existing buildings - A guide for Building Consent Authorities and Territorial Authorities” to help Building Consent Authorities (BCAs) or Territorial Authorities (TAs) decide what information on means of escape from fire to request, as part of a building consent application, to alter an existing building.

Where an ANARP assessment of means of escape from fire is undertaken using the C/VM2 method, the FEB process is part of that method.

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3.2 When does the Fire Service Commission become involved in a building consent application?

New Buildings for Protection from Fire using the Acceptable Solutions (C/AS1 – C/AS7) or Verification Method (C/VM2) do not need to be sent to the Fire Service Commission at the consent stage.
Designs need to go the Fire Service Commission for advice if:

  • compliance with clauses C1-6, D1, F6, or F8 of the Building Code will be established by alternative solution – this would be the case, for example, for building types such as power generation plants, dairy factories, sub-surface buildings, or tunnels (the scope of the Acceptable Solutions or the Verification Method does not include these types of buildings).
  • the consent application involves a modification or waiver of clauses C1-6, D1, F6, or F8 of the Building Code under Section 67 of the Building Act 2004.
  • the consent application is for an alteration, or change of use to an existing building, except where the effect on fire safety systems is minor.
  • The above instances do not apply if the building is an exempt building. The following buildings are exempt:
    • single household unit
    • vertically separated household unit with independent egress
    • outbuilding or ancillary building
    • internal fit out-unless it relates to ‘change of use’
    • outbuildings or ancillary buildings
    • premises of diplomatic missions
    • any Crown buildings specified by Gazette notice.

For more information

This explains the requirements of the gazette notice of 3 May 2012 and clarifies when a design needs to be sent to the Fire Service Commission.

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3.3 When is a fire-engineering brief required as part of the building consent documentation?

If a building consent application uses the Verification Method C/VM2 to show compliance with Code Clauses C1 to C6, a fire engineering brief (FEB) process, including a FEB report, is required as part of the consent documentation. The FEB process has to involve all stakeholders in the building, including but not limited to, the following:

  • building owner and users
  • design professionals
  • Fire Service Commission
  • building consent authority (BCA)
  • insurer
  • test certifier, if hazardous substances are in the building.

This means that the Fire Service Commission is included in the design process at an earlier stage than previously.

For more information on FEBs

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3.4 Are the uses in Schedule 2 of the Building Specified Systems, affected by the Protection from Fire documents?

The Protection from Fire documents do not affect the ‘uses’ specified in Schedule 2 of the Building (Specified Systems, Change the Use, Earthquake-prone Buildings) Regulations 2005.

Notes: The ‘uses’ specified in Schedule 2 are often confused with ‘purpose groups’ from Acceptable Solution C/AS1 (2011) and ‘risk groups’ from Acceptable Solutions C/AS1 to C/AS7 (2012). ‘Purpose groups’ and ‘risk groups’ are not related to ‘change of use’.

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3.5 How do I determine a ‘change of use’?

Schedule 2 of the Building (Specified Systems, Change the Use, Earthquake-Prone Buildings) Regulations 2005 helps identify if there is a change of use to the building.

To determine if there is a ‘change of use’ to a building:

  • Firstly, refer to Schedule 2 of the Building Regulations (Specified Systems, Change the Use, Earthquake-Prone Buildings) Regulations 2005 to confirm if the building is being used for another function. For example, changing a building’s ‘use’ from apartments (SR) to a day-care centre (CS).
  • Secondly, determine if the new use is more onerous than the old use in terms of complying with the Building Code. In the above example, a day-care centre would be more onerous as there are additional Building Code requirements including more fire safety requirements and additional requirements for access and facilities for people with disabilities.

If both of the above are satisfied, then the proposed new use is deemed a ‘change of use’.

For more information on ‘change of use’

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3.6 Is there any guidance about ‘change of use’ under section 115 of the Building Act?

MBIE published guidance for Change of Use for the Christchurch City Council to help them deal with changes of use for temporary business and/or housing relocations because of the Canterbury earthquakes. Although developed for Christchurch, the guidance explains the ‘change of use’ provisions in the Building Act and associated regulations, and provides practical advice on how to apply these.

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3.7 Which Building Code clauses are relevant to assessing the attributes of a building that relate to ‘means of escape from fire’ (as referred to in sections 112 and 115 of the Building Act 2004)?

When the Building Act 2004 requires an assessment of the ‘means of escape from fire’ in a building, compliance with the following Building Code clauses must be considered:

C3.4 Fires affecting areas beyond the fire source »
C4 Movement to place of safety »
D1 Access »
F6 Visibility in escape routes »
F7 Warning systems »
F8 Signs »

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3.8 Will past determinations applied to the superseded C1 – C4 Building Code Clauses be applicable as guidance for the current C1 – C6 Building Code Clauses?

Determinations applying to Code Clauses C1-C4 and C/AS1 (2011), do not apply to the current Code Clauses C1-C6 and the Acceptable Solutions C/AS1-C/AS7, and Verification Method C/VM2 (2012).

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3.9 Can a design based on the Acceptable Solution incorporate aspects of the Verification Method and still comply with the Building Code?

A design based on an Acceptable Solution, (C/AS1 to C/AS7) must completely comply with all the requirements of the Acceptable Solution. It cannot incorporate aspects of the Verification Method and still be used to show compliance with the Building Code.

However, there is one exception, when the only non-compliance with the Acceptable Solution relates to the prevention of horizontal spread of fire. In this instance, a suitably qualified fire engineer may use the C/VM2 methodology to show compliance with this aspect of the Building Code.

This applies to both the extent of unprotected area using the methods described in Design Scenario (HS): Horizontal fire spread and the fire resistance rating of the external wall using the ‘full burnout design fire’.

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3.10 Where can I find the Code clauses, Acceptable Solutions, and Verification Methods referenced in these questions and answers?

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3.11 Why is a Fire Engineering Brief (FEB) required for C/VM2 designs?

A FEB is, “a documented process that defines the scope of work for the fire engineering analysis and the basis for analysis as agreed by stakeholders” (IFEG). The FEB gives the opportunity for comments and consensus on the fire safety components of the schematic design.

This opportunity to receive feedback and achieve consensus in early design stages reduces consenting risk, and avoids rework where an issue with the fire design is not identified until consent stage, such as:

  • changes to the fire design solution arising from changes to design assumptions made during preliminary design
  • rework by all design disciplines to change the coordinated design and re coordinate the drawings
  • delays late in the design if complex fire models have to be altered and re run

The FEB process identifies issues before the designs are fully developed and therefore avoids the rework and delay described above.

“A fire engineering brief (FEB) should be prepared… This task is of fundamental importance and forms the basis of the fire engineering process.” IFEG

The FEB purpose is to set down the basis, as agreed by the relevant stakeholders, on which the fire safety analysis will be undertaken. A fire engineer should provide guidance on and technical justification for decisions made during the FEB process on matters including but not limited to:

  • design fire locations
  • design occupant groups
  • analysis strategy, including the selection use and design parameters of any computer based design tool

The fire engineer needs to ensure the actual process used is appropriate for the design or evaluation. Where the fire engineering analysis considers a simple well defined problem, the FEB may be a short document, whereas complex and / or large projects could require a more substantial document. In order to achieve its purpose the FEB should be developed with input from the relevant stakeholders.

The consent review verifies that issues raised during the FEB process have been addressed in the consent documents submitted. This speeds up the consent review.

The intent of the FEB is to reduce compliance costs and avoid unexpected delays.

For more information on FEBs

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3.12 Why was a concession for unrated intermediate floors consulted on but not included?

In the recent amendment to the Acceptable Solution and Verification Method, provisions for unrated (intermediate) flooring systems were considered. Due to a number of issues raised these were not incorporated in the final amendment, these issues include but were not limited to;

  1. Concern that a perforated floor could not protect occupants for a sufficient duration to enable egress, particularly where there are single direction of escape travel paths on the floors requiring people to pass near to or over the fire.
  2. Depending on the layout, disproportionate collapse was a concern e.g. where a localised fire exposing a supporting column could cause a floor platform to suddenly fail.
  3. Fire fighters are unable to adequately risk assess an unrated solid floor in a fire event, they have no way of knowing whether the floor is structurally able to withstand the weight of fire fighters and their equipment.
  4. Stacked imperforate flooring areas are a significant challenge for adequate sprinkler protection, the sprinkler standard does not set out provisions to address the particular risk of protecting multiple unrated perforate floors.

While not all of these issues would likely relate to any individual instance of an unrated (intermediate) floor, these and other challenges raised during work group discussions lead to the conclusion that further detailed investigation and guidance is necessary before implementing a concession for unrated floors. It was therefore, not implemented in either the Acceptable Solutions or Verification Method C/VM2.

Further work is planned to investigate the challenges associated with unrated floor systems so that, if appropriate, design guidance can be developed and published.

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3.13 When is the updated Commentary to Acceptable Solutions C/AS1-7 and Verification Method C/VM2 due to be published?

The publishing of these commentaries will occur at a later date. However to support the July 2014 Amendments the following information is provided.

C/AS3 & C/AS4 Paragraph 4.16.12 Fire dampers


Smoke control system shut down on alarm activation, on its own, is not sufficient where a delayed evacuation strategy is in place. The commentary provides further guidance on smoke control in air handling in this case.


There is an additional requirement where evacuation is delayed for ventilation ducts that pass through a fire and/or smoke separation. The performance of the smoke separating function must also not be compromised and a smoke damper (complying with AS/NZS 1668.1) is required. Delayed evacuation relates to any evacuation regime other than all building occupants moving directly to a place of safety outside, simultaneously and immediately on detection of fire.

C/VM2 Paragraph 1.2 Scope


There are some minor exceptions to ‘all buildings’, for example tunnels and open air stadia. Users should refer to the Commentary to this Verification Method for further information.


When using other fire engineering design methodologies, designers are expected to exercise care and intelligent application of those design methodologies in the context of the New Zealand Building Code’s quantitative performance criteria. This is because compliance with other design methodologies does not in itself demonstrate compliance with the New Zealand Building Code.

C/VM2 Paragraph 2.2.1 Fire Modelling Rules for Life Safety Design

e) All doors not described in Paragraph 2.2.1 b), c) and d) shall be considered to be open during the analysis unless for substantiated functional reasons as established at FEB the doors can be shown to be closed throughout the time period of analysis (see Commentary).


An exception permitted by this Verification Method to the requirement to model doors as open (other than those listed in 2.2.1 b), c) and d)) is for doors which need to be closed for essential functional reasons or for which there is a high likelihood that they will be closed most of the time for security or other functional reasons. It is reasonable for the Building Consent Authority to accept specific doors to be closed for fire modelling purposes where the building owner can justify on reasonable grounds the basis for this expectation.

C/VM2 Paragraph 2.5 Equivalent Time of Exposure


Further guidance on the applicability of this approach and a suggested procedure is given in the commentary.


The time period for which the construction is required to perform (if not explicitly stated in C/VM2) will depend on the function of the structural or separating element which will either be for life safety, fire-fighting or property protection. Fire resistance rating shall be provided as follows:

  • If the purpose of the element is property protection then a full burnout fire rating will apply.
  • Paragraph 4.8 Design Scenario (FO) Fire Fighting Operations describes which elements are required for fire-fighting and fire resistance rating is either burnout fire rating or derived from the period required to resist collapse.
  • If the element is for life safety only for use while the occupants evacuate, the specified period of time referred to in C/VM2 Paragraph 2.5 will generally be the RSET as determined by Paragraph 3.2 Required Safe Time to Evacuate.

C/VM2 Pre-travel Activity Times - Table 3.3 Buildings Where the Occupants are Considered Sleeping and Detained under the Care of Trained Staff (eg, prisons etc)


The time taken for staff to respond to a fire alarm and attend the area where the fire alarm has occurred varies considerably.  For this reason it is not possible to assign a fixed value either for pre-travel activity time or the duration of the evacuation once it is initiated, as each detention facility will be different. For detention facilities the selection of a pre-travel activity and evacuation time should be determined after consultation with facility management who will need to advise on staff movements and the likely evacuation procedure /duration to complete.  The pre-travel activity and duration of the evacuation should be included and agreed to by the stakeholders as part of the FEB process.

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3.14 How timber linings can be used in certain crowd uses

The content below provides guidance for designers enabling them to submit for building consent based on a modification of Building Code Clause C3.4 (a) where Group Number 3 timber is proposed in crowd occupancy areas requiring Group Number 2.

Material Group numbers are described in the Building Code and the requirements are repeated within Acceptable Solutions C/AS1-7 relevant to each risk group. Group numbers are aligned with general building uses and can be broadly summarised as follows:

Group Number Building Use
Group Number 1 Exitways, Importance level 4, Sleeping Use with Care or Detention
Group Number 2 Crowd & Sleeping Use except within household units
Group Number 3 All Other Uses

It is important to ensure that materials used as internal surface linings do not unreasonably contribute to the fire risk including in crowd areas. These areas generally contain people who are unfamiliar with the building and its escape routes.

Crowd use is any of the uses within CS (Crowd Small), CL (Crowd Large), CO (Crowd Open) or CM (Crowd Medium) as defined in Schedule 2 of the Building (Specified Systems, Change of Use, and Earthquake-Prone Buildings) Regulations 2005.

It is however acknowledged that smaller premises used for crowd activities may by their nature have a low occupancy and efficient escape route features. Escape time in the event of a fire is therefore shorter and the probability of Group 3 internal surface finishes adversely affecting the ability to escape may be low. These can be used to justify applying for building consent based on a modification to Clause C3.4(a) to the effect that a material with Group Number 3 can be used.

Criteria to be included in justifying that the proposed modification is reasonable in a particular instance include:

  • Escape route widths are double that required by Paragraph 3.3.2 of the relevant Acceptable Solution, and
  • Open paths travel distances are half that specified in Table 3.2 of the relevant Acceptable Solution, and
  • Finished floor to ceiling height is more than 3m, and
  • The occupancy of the space is less than 250 people, and
  • The firecell is at ground level and are served by at least two exitways or final exits.

The above consideration does not extend to exitways within crowd uses.

Where the above criteria are met Council, after taking advice from the Fire Service as required by Gazette Notice 49 may well consider it appropriate to issue a modification to Building Code Clause C3.4 (a) under Section 67 of the Building Act for crowd uses which would permit use of solid timber surface linings in buildings such as community halls, cafes, schools, recreation halls, small shops, and restaurants.

There are likely to be circumstances where these criteria are not met in full and if so designers need to look at the facts in each instance and put their arguments forward to Council justifying why they believe the modification is nevertheless reasonable.

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