2022 NCC Seminars: Volume One - Definitions

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[Music]  

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Hello, my name's Graham Moss I'm the Principal Building Surveyor for the Australian Building Codes Board.  

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This video is a short update on changes to NCC  2022 in the definitions for BCA that's

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Volumes One and Two of the NCC. So the first definition  change is how we've replaced average recurrence  

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interval with annual exceedance probability. Now this change makes the BCA consistent with  

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the AS 3500 series which uses the term annual  exceedance probability. Now average recurrence  

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interval, average exceedance probability these  are actually two different ways of saying the  

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same thing and that is the likelihood of a given  event occurring in any given year and of course  

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for these defined terms it's the likelihood of a  given rainfall event occurring in any given year.  

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The next definition changes the introduction of a  new defined term building complexity but before I  

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show it to you I'm going to show you some trivia, the number of occurrences of defined terms in  

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the BCA. So required I think is the most popular  defined term in the BCA it's got 1033 occurrences  

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across both volumes. I was surprised by performance  solution I thought it wouldn't occur as often as  

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it does but 620 times you see the defined term  performance solution used in BCA Volume One and Two.  

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Now outdoor air I like this defined term I don't  know about you but I like defined terms I quite  

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enjoy definitions possibly that's saying more  about me than it does about the definition for  

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building complexity, however outdoor air  is not a very popular defined term it's  

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used seven times in Volume One, four times  in Volume Two,only eleven times, so why is  

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outdoor air one of my favorite definitions  well the definition for outdoor air is air  

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outside the building. Now does that not appeal  to you it appeals to me I think it's amusing  

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so that's why I was sad when I only found that  used 11 times in the BCA. So building complexity  

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trivia for you how many times do we see the  words building complexity used in a defined sense  

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in the Building Code of Australia for NCC 2022, zero. It makes outdoor air look popular doesn't it.

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Now building complexity is a new concept included  in NCC 2022 it's a way of grading buildings by  

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complexity but we don't use it in the BCA we  don't use it in the NCC entirely. Now why are we  

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including it well it could be that we would use it  in the NCC in the future but also in the meantime  

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it may be that state or territory legislation  would refer to this definition and require for  

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instance that higher complexity buildings would  require further scrutiny, such as peer review.

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So that's why we've included it despite not  using it now I'm going to show how building  

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complexity works it works by the four criteria  that you see in the blue boxes on this slide  

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we have attributes and that's where the  building exceeds 25 meters effective  

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height or has performance solutions for fire or  structure or is in a place of natural hazard for  

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instance the bushfire prone land. If you trigger  all of those or even just one of those attributes  

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criteria then that's triggered that criteria  box and you have one criteria for complexity.

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Next is Class 2, if your building is Class 2 then  that criteria applies, occupant number if you have  

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more than 100 occupants in the building that's  also a criteria and fourthly occupant ability  

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if more than 10 of those occupants require  evacuation assistance then you've triggered  

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that criteria and of course as you go about  triggering criteria your score increases and  

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you get a higher level of complexity, low for one  criteria, medium for two criteria you get the idea.

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If all four criteria are triggered well that's  very high building complexity it's also the case  

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that if your building is importance level 4 or  importance level 5, so of course we're talking  

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about buildings essential for both disaster  operations like hospitals for instance. If you  

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have an IL4 or IL5 building then of course that's  straight away a very high building complexity.

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This next change is a new defined term for  volume and that applies for BCA Volume One.  

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since its first edition the BCA has had  a definition for floor area but the BCA  

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has never had a definition for volume. Now the  concept of volume is used a handful of times in  

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BCA Volume One they're listed on this slide  here C3D3 for general floor area and volume  

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limitations, C3D4 which uses the concept of  volume to describe a large isolated building,  

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E1D8 for some Class 6 buildings of a certain  volume sprinklers are required and there's also  

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smoke hazard provisions required in E2D10  for large isolated buildings again that concept  

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of volume is used to describe a building for which  this smoke has a management provisions apply.  

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Now sometimes at the ABCB office we've been receiving  calls where people say look I'm doing a volume  

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calculation like for instance I'm trying to find  the maximum volume of my compartment and I've got  

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this space in the building like in the photograph  here where there's all these trusses in the way no  

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one's going to use that space so can I remove that  space for the purposes of calculating my volume. 

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Well the answer that question is no because  that area is within the building within the fire 

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compartment and therefore of course contributes  to the volume for the purposes of C3D3.

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So what we've done for NCC 2022 is introduced this  new defined term volume in order to clarify that  

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and other things, now it might look complex but  actually what we're doing with this defined term  

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is taking the various scenarios for which the  concept of volume applies and setting up what  

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the Deemed-to-Satisfy provisions require  to be contributing to the volume calculation.