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In the last decade infill housing, housing built behind or in front of an existing dwelling on the same allotment, has become more common as developable land has become more and more scarce. These infill dwellings may be detached standalone dwellings or attached townhouses, either way they can raise a myriad of compliance issues when built close to an existing dwelling on a single allotment, notably how occupants may escape to a place of safety e.g. the street, in the event of fire.
Until recently C/AS1, the acceptable solution for houses, townhouses, small multi-unit dwellings and outbuildings (risk group SH) was silent on providing external escape routes in these situations raising concerns within Building Consent Authorities and at FENZ (Fire Engineering New Zealand).
These concerns were exemplified in Determination 2019/062, concerning a new infill dwelling built behind, and on the same allotment as an existing dwelling. In the determination, MBIE made clear that if C/AS1 is used as the means of compliance for a new detached dwelling then the building code objective is only concerned with escape from fire from the ‘subject building’. As the occupants could escape the subject dwelling via a pathway alongside the existing building the proposed external means of escape was deemed compliant with the requirements of C/AS1 and therefore the Building Code. This outcome, and C/AS1, did not consider occupant expectations and human behaviour if the neighbouring dwelling that the occupants are expected to escape past was on fire.
The expectation when the compliance document was drafted was that all detached dwellings would have simple access to the street. It could be reasonably expected that if the subject dwelling was not the dwelling on fire, then the neighbouring dwelling could be considered a ‘place of safety’ (of adequate distance to the on-fire dwelling) where occupants could stay and be safe or easily disperse to the street without passing the on-fire dwelling. These expectations don’t align with human behaviour in events as expressed by FENZ,
‘but noted that it (FENZ) does have broader concerns with regards to multiple dwellings on one site and in particular where there are narrow non-fire protected routes past the dwelling and/or less open space between the dwellings’,
and have not kept up with the changing ways and places where houses and townhouses are being built.
In November 2023 MBIE released an updated C/AS1 which goes some way to addressing these life safety concerns around external means of escape in these situations.
The changes noted under the new Section 3.3.5 of C/AS1 require the below:
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These changes, will apply to both attached and detached dwellings, are better aligned with the types of housing currently being constructed across Aotearoa and the way people actually react in an event, where the instinct is to get as far away as possible and to a place where it is easy to escape from in the case of an event whether you are an occupant of the subject building or a close neighbouring one
The above requirements will need to be considered for all new dwellings going forward and must be adhered to from November 2024 to demonstrate compliance with C/AS1 if this is the proposed method of compliance. Where alterations are being made to existing dwellings these will need to be assessed under Section 112 of the Act, Alterations to Buildings with the new requirements for full compliance a consideration in the assessment.
C/AS1 is not the only means of compliance with the building code however and all buildings must have a safe means of escape from the building to meet the performance requirements of the Building Code and ensure the life safety of the building occupants. When designing or assessing a means of escape from a building whether the escape route incorporates internal or external parts you should check that it includes all of the following parts.
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Escape Route – A continuous unobstructed route from any occupied space in a building to a final exit to enable occupants to reach a safe place, and shall comprise one or more of the following: open paths and safe paths (protected paths are included in the definition of escape route in Clause A2. Final Exit – The point at which an escape route terminated by giving access to a safe place. Safe Place – A place, outside of and in the vicinity of a single building unit, from which people may safely disperse after escaping the effects of a fire. It may be a place such as a street, open space, public space, or an adjacent building. Open Space - Means land on which there are, and will be, no buildings and which has no roof over any part of it other than overhanging eaves. Open Path – The part of an escape route (including dead ends) within a firecell where occupants may be exposed to fire or smoke while making their escape. Dead End – That part of an open path where escape is possible only in one direction. A dead end ceases to exist where the escape route reaches a point in the open path which offers alternative directions of travel, or at a final exit or an exitway. Safe Path – The part of an exitway which is protected from the effects of fire by fire separations, external walls, or by distance when exposed to open air. |
The updates to C/AS1 show that to meet building code compliance the life safety of the occupants can extend outside of the building envelope and must consider the environment around the building to ensure people can disperse safely in an event.
You can find the full raft of changes to C/AS1 and the new updated changes on MBIE’s website.
For other new requirements in C/AS1 you can also see our article on the new requirements for Interconnected Smoke Alarms.