I have a project on my desk that is making me go “hmmm” – and another similar one I am waiting for some more documentation on. Both recent designs by people who should and do know better.
Anyone have any comments on the following and my interpretation?
It is a residential building with ground level non-residential use firecell(s), and a concrete roof deck over forming a podium and on this are some terrace houses, which if they were on the ground would clearly be risk group SH with a redesign of a shared stair in some units.
The designer in this case has decided that the apartments/ townhouses are in fact SH, despite sitting on a podium. There are a huge number of advantages for this, saving probably around a million dollars in construction cost. Lower fire ratings between units, domestic smoke alarms instead of a type 5, no fire rating to boundaries more than 1m away (so large ranchsliders are allowed and no fire rated windows), longer travel distance inside the units, etc.
The escape route for each unit goes onto the podium as an external escape route and then to the ground by 2 internal stairs.
If each apartment is a townhouse, how many extra floors can you add under it before it ceases to become a townhouse?
In my opinion it is wrong and deliberately so.
“1.1.2 Buildings or parts of buildings in risk groups other than SH are outside the scope of this Acceptable Solution. Refer to Table 1.1 and use the corresponding Acceptable Solution instead.”
The building is a single building as defined by the Building Act and the normal usage of the word. As it is a building that contains other risk groups (other than the residents’ garages) then it cannot be SH.
C/AS1 also states that it is for
b) Multi-unit dwellings with no more than one unit above another (see Figure 1.1) and where each unit has an escape route independent of all other units, and including associated garages or carports whether or not they are part of the same building
Escape route is a defined term in the Act.
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.
The podium is not a safe place as this is defined as
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 unit
By definition the podium is a shared escape route until you go down the stairs to the outside of the building. By this reason alone, they cannot be SH risk group and must be SM apartments with all that involves.
Does anyone disagree with this interpretation?