Office buildings and fire engineering. We all knew this was coming.
Since office buildings come in all shapes and sizes, the list of common Performance Solutions is not as easy to prepare when compared to warehouse developments or retail developments. There are some recurring themes in some of the developments we have worked on as fire engineers though and they are presented below.
Extended Exit Travel Distances
Background
Class 5 office buildings enjoy the same allowances for egress travel distances that Class 6 retail buildings do under NCC 2019 Amendment 1:
Up to 20 metres travel to an exit or a point where travel to a choice of two different exits is possible within a total of 40 metres travel.
If the level discharges directly to road or open space, the travel distance to an exit may be extended to 30 metres.
Although some multi-storey office buildings are designed with fire stair located centrally within the building and the travel distances work, SOME designers like to challenge fire engineers by positioning these stairs in the remote corners of buildings and, when combined with internal partitions, is the perfect storm.
Performance Solution
To permit extended egress travel distances to a building exit
Although CFD may be the preferred method of approach for reviewing extended egress in warehouse and retail buildings, office buildings do not typically share the tall ceilings and as such, smoke and heat won't have anywhere to go and quickly settle at the occupant exposure height. The outcome will likely demonstrate a very quick onset of untenable conditions likely well before occupants can evacuate.
The intent is to still review the Required Safe Egress Time (RSET) however, a comparative approach shall be adopted to compare how quickly occupants evacuate under the extended travel distance scenario versus a scenario where Deemed to Satisfy complying travel distances are in play. The relevant criterion:
RSET (Extended Travel) <= RSET (Deemed to Satisfy)
This sort of approach works only when the proposed extended travel distance scenario incorporates some fire safety measures over and above the Deemed to Satisfy scenario such as automatic fire sprinkler protection, automatic fire detection or smoke hazard management system.
These systems will work to reduce the RSET by speeding up the time until occupants become aware of the fire.
Interconnection of Multiple Storeys
Background
The evolution of functional office design sees a wider-spread introduction of multi-floor office tenancies with an open stair interconnecting them to give the impression of greater worker efficiency.
The Deemed to Satisfy provisions of the NCC 2019 Amendment 1 (Clause D1.12) allow office buildings to have two interconnected floors with an open stair provided the stair is not used for egress. A third storey may be permitted to be connected where the building is fully sprinkler protected. That is on the proviso that one of the floors open directly to road/open space.
For interconnections not complying with the above, they'll be considered an atrium which comes with a host of requirements under NCC 2019 Amendment 1 clause G3 that are not conducive to free-flowing architectural design.
Performance Solution
To permit interconnection of more than 3 storeys or interconnection where none of the storeys connect directly to the level of road/open space
The most basic form of justification which may work depending on the type of building would be to introduce a fire curtain at one or multiple storeys to create passive fire separation between the void and particular building levels. As the stair is not relied upon for egress, the closure of the stair via the dropping curtain may not have an impact on egress.
Smoke Control are an Australian company who offer a range of curtains to suit custom designs (not a plug! I don't work for them). Below is a link to one of their typical products.
Extended Hydrant Hose Length Coverage
Background
Why are we not surprised to see this Performance Solution on this list. You can generally blame the high powered business executives who want an office in the corner of the building which also so happens to be the most remote point from the fire hydrant. Although hydrants have a maximum reach of up to 60 metres (externally) or 30 metres (internally) under Australian Standard 2419.1-2005, one tiny detail the standard requires is that the hose must extend a minimum of 1 metre into each room before applying the hose stream.
The fire brigade are generally not very friendly to accepting solutions like these as it increases the weight of their equipment to carry to the hydrant (which could span multiple storeys!). Some clever fire engineering may be needed here.
Performance Solution
To permit the use of an additional hydrant hose length for full building coverage
Similar to a warehouse or retail situation, fire brigade agreement is critical and all the relevant tools must be employed to demonstrate that fire brigade operations have been considered. The Fire Brigade Intervention Model (FBIM) can work wonders.
Compromised Fire Hose Reel Coverage
Thought you almost caught us out in a mistake didn't you? Our fire engineers are always on top of the most recent and upcoming developments to the National Construction Code. The NCC 2019 Amendment 1 incorporated a commonly proposed Performance Solution into their Deemed to Satisfy provisions.
Specifically, fire hose reels CAN BE OMITTED for Class 5 office buildings. Architects rejoice that this is no longer something that needs to be negotiated.
Conclusion
Office buildings have fewer "typical" Performance Solutions than retail buildings or warehouses but it doesn't mean there aren't any ways that we can provide value to your project as fire engineers.
Get in touch with us on your next retail project and experience the outcomes we can achieve for you.