SFPE Discussions

New C/AS2 vs C/AS1 SH scope definition

We are currently drafting a fire report for a 3 level building, 2 level major dwelling above a single level minor dwelling (both with independent escape routes) and noted a change to the SH scope wording in the new C/AS2 which seems to clash with the still current C/AS1. The new C/AS2 has added wording “…no more than two levels …” in table 1.1, whereas C/AS1 just limits you to no more than one unit above another. Fig 1.1. in C/AS1 IMPLIES that you can’t have more than two levels?

Perhaps something else that MBIE needs to clarify in the next amendments? In the meantime we’re left wondering whether this house is risk group SH or SM (with the added requirement of a type 5 since the travel distances off the intermediate floor are greater than 20m when applying the 1.5 multiplier!).

If we elect to show compliance with C/AS1 someone could point out that MBIE guidance states it is clearly risk group SM so I guess we’re stuck with SM for now.

I would have thought when using C/AS1, you should use the scope definition within that document (C/AS1) as it should still stand until amended or withdrawn.

For more clarification on floors vs units, the old commentary to C/AS1 - C/AS7 states in part:

"Risk group SH Risk group SH applies to detached houses and to buildings containing
a number of separate residential units, provided there is no more than one unit above another.
Therefore, the Acceptable Solution covers the fire safety requirements for a row of townhouses
and maisonettes as well as two-storey apartment blocks.
While each household unit may have more than one floor, it must still have its own independent
escape route. If the building provides a shared escape route, then C/AS2 will apply."

As such, I would suggest this falls squarely within SH, but perhaps a discussion with Council to get their buy in to the logic.

Hi Rob
C/AS2/4.13.8 removes all the ‘intermediate floor’ requirements therefore although Table 1.1 refers to two units above each other 4.13.8 permits intermediate floors within each unit. You could likely have two 3-level units above each other provided the escape length works out.
In fact Table 1.1 even defines what it means by virtue of the bracketed clause meaning that a level is actually a household unit within which there may also be 1 or 2 intermediate floors.

Thanks Luke, I agree, definitely worth a chat with Council. The excerpt from the old commentary is very helpful, confirms my understanding of how many levels you were permitted under C/AS1.