This video from the 2022 NCC Seminars discusses Schedule 1 Definitions from NCC 2022 Volume One.
Hello, my name's Graham Moss I'm the Principal Building Surveyor for the Australian Building Codes Board.
This video is a short update on changes to NCC 2022 in the definitions for BCA that's
Volumes One and Two of the NCC. So the first definition change is how we've replaced average recurrence
interval with annual exceedance probability. Now this change makes the BCA consistent with
the AS 3500 series which uses the term annual exceedance probability. Now average recurrence
interval, average exceedance probability these are actually two different ways of saying the
same thing and that is the likelihood of a given event occurring in any given year and of course
for these defined terms it's the likelihood of a given rainfall event occurring in any given year.
The next definition changes the introduction of a new defined term building complexity but before I
show it to you I'm going to show you some trivia, the number of occurrences of defined terms in
the BCA. So required I think is the most popular defined term in the BCA it's got 1033 occurrences
across both volumes. I was surprised by performance solution I thought it wouldn't occur as often as
it does but 620 times you see the defined term performance solution used in BCA Volume One and Two.
Now outdoor air I like this defined term I don't know about you but I like defined terms I quite
enjoy definitions possibly that's saying more about me than it does about the definition for
building complexity, however outdoor air is not a very popular defined term it's
used seven times in Volume One, four times in Volume Two,only eleven times, so why is
outdoor air one of my favorite definitions well the definition for outdoor air is air
outside the building. Now does that not appeal to you it appeals to me I think it's amusing
so that's why I was sad when I only found that used 11 times in the BCA. So building complexity
trivia for you how many times do we see the words building complexity used in a defined sense
in the Building Code of Australia for NCC 2022, zero. It makes outdoor air look popular doesn't it.
Now building complexity is a new concept included in NCC 2022 it's a way of grading buildings by
complexity but we don't use it in the BCA we don't use it in the NCC entirely. Now why are we
including it well it could be that we would use it in the NCC in the future but also in the meantime
it may be that state or territory legislation would refer to this definition and require for
instance that higher complexity buildings would require further scrutiny, such as peer review.
So that's why we've included it despite not using it now I'm going to show how building
complexity works it works by the four criteria that you see in the blue boxes on this slide
we have attributes and that's where the building exceeds 25 meters effective
height or has performance solutions for fire or structure or is in a place of natural hazard for
instance the bushfire prone land. If you trigger all of those or even just one of those attributes
criteria then that's triggered that criteria box and you have one criteria for complexity.
Next is Class 2, if your building is Class 2 then that criteria applies, occupant number if you have
more than 100 occupants in the building that's also a criteria and fourthly occupant ability
if more than 10 of those occupants require evacuation assistance then you've triggered
that criteria and of course as you go about triggering criteria your score increases and
you get a higher level of complexity, low for one criteria, medium for two criteria you get the idea.
If all four criteria are triggered well that's very high building complexity it's also the case
that if your building is importance level 4 or importance level 5, so of course we're talking
about buildings essential for both disaster operations like hospitals for instance. If you
have an IL4 or IL5 building then of course that's straight away a very high building complexity.
This next change is a new defined term for volume and that applies for BCA Volume One.
since its first edition the BCA has had a definition for floor area but the BCA
has never had a definition for volume. Now the concept of volume is used a handful of times in
BCA Volume One they're listed on this slide here C3D3 for general floor area and volume
limitations, C3D4 which uses the concept of volume to describe a large isolated building,
E1D8 for some Class 6 buildings of a certain volume sprinklers are required and there's also
smoke hazard provisions required in E2D10 for large isolated buildings again that concept
of volume is used to describe a building for which this smoke has a management provisions apply.
Now sometimes at the ABCB office we've been receiving calls where people say look I'm doing a volume
calculation like for instance I'm trying to find the maximum volume of my compartment and I've got
this space in the building like in the photograph here where there's all these trusses in the way no
one's going to use that space so can I remove that space for the purposes of calculating my volume.
Well the answer that question is no because that area is within the building within the fire
compartment and therefore of course contributes to the volume for the purposes of C3D3.
So what we've done for NCC 2022 is introduced this new defined term volume in order to clarify that
and other things, now it might look complex but actually what we're doing with this defined term
is taking the various scenarios for which the concept of volume applies and setting up what
the Deemed-to-Satisfy provisions require to be contributing to the volume calculation.