Ç/AS2 (2017) Paragraph 3.9.6


I recently had a pre-app meeting with a BCA with regards to a new multi-use 5-storey building - GF car park, 1st to 3rd floor office and top floor permanent accommodation for a single household (which happens to be the building owner). The building is not unit or strata titled. Also the building is served by a single safe path stair connecting all floors. Given the car parks on the ground floor, escape height > 10m in that single stair and having other Risk Groups on the lower floors than the SM Risk Group. Hence, A Type 7 system is required.

The part where I couldn’t fully understand is that why a fire rated lobby (act as a horizontal safe path) preceding the vertical safe path is required when a smoke lobby (with lesser protection) is not even required at that top most level. Unless I have missed something here the interpretation of paragraph 3.9.6 by the BCA seems contradicting with other requirements in the fire code for this particular scenario. Granted, it makes sense if there was a common corridor serving multi sleeping area firecells, e.g. motel units, hotel rooms or apartments but I just don’t see this is the case here.

I would have thought that 3.9.3b removes that requirement as the firecell is sprinklered with the Type 7.

That requirement has not been looked at since it was changed from the old C/AS1 document where the requirement had three choices with the third being a pressurised vertical safe path. It is not clear why the pressurisation option was removed but it indicates that the purpose of the horizontal safe path would be to limit the effects of fire ending up in the stairwell.

There are probably other reasons why a horizontal safe path is needed. Perhaps it is anticipated in most cases there will be multiple apartments, or it could be an allowance for FENZ to carry out rescue or firefighting.

Thanks John. I am also aware of paragraph 3.9.3b which clearly removes the smoke lobby requirement, yet again BCA turned his head and fixated on paragraph 3.9.6.

Thanks Kenneth. I wish there is a way that we can be shared with the actual design intent(s) behind each of those requirements in the Compliance Documents, instead of us second guessing what are they really there for.

I would have thought the fire separation to the vertical safe path is more than sufficient to stop the fire spread into the stairwell. Also, I note the lower floor offices with a much higher fuel load and occupant load potentially posing a much high risk of fire spreading into the stair do not require any horizontal safe path to precede the vertical safe path.

The FENZ search and rescue may be a plausible reason but similarly this was not a consideration nor a requirement for the lower office floors.

Now that MBIE are starting a review of the approved documents every two years it is worth making submissions for potential improvements. MBIE was mostly receptive to the public comment phase of C/AS2.

There is always room for improvement but the Acceptable Solutions are a one size fits all approach which might not be the best approach depending on the project.

Many of us would like to understand the reasoning behind certain requirements as it would allow for more sophisticated decision making.

Perhaps MBIE can also clarify if this requirement only applies to where it serves more than one sleeping firecell? As it clearly states “firecells” under 3.9.6. It can potentially create loop holes if some people trying to interpret word by word…