2022 NCC Seminars: Volume Two - Masonry

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[Music]

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My name is Phil Finnimore, with the Australian Building Codes Board and  today I'm going to talk to you about masonry  

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construction and the details within Volume  Two and the Housing Provisions of NCC 2022.

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H1D5 of Volume Two sets out the Deemed-to-Satisfy pathways shown in this slide. On the right hand  

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side is AS 3700 or the 4773.1 and .2 suite of  standards. This is known in 2019 as an acceptable  

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construction manual simply referenced in the  Housing Provisions for 2022 as reference documents.

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If you choose this path they're the relevant  standards if you don't choose this path you can go  

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to Part 5.4, that's on the left hand side of this  slide, which are the Deemed-to-Satisfy requirements  

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set out in the Housing Provisions for 2022. So to  be clear for masonry there's a choice a complete  

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choice between a referenced Australian Standard  3700 or 4773 or Part 5.4 of the Housing Provisions.

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Comparisons between 2019 Volume Two and the Housing Provisions  

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which is where the Deemed-to-Satisfy requirements are for masonry construction

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on the left Part 3.3 2019 starts at 3.3.1 go  through go through to Part 3.3.6

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unreinforced masonry all the way  through to ice isolated masonry repairs.

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What we've changed for NCC 2022 is the addition  of cavity masonry Deemed-to-Satisfy requirements  

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and unreinforced single leaf masonry requirements. These are in addition to those of 2019 and I'll

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talk about some details of those and how Volume Two connects those to the Housing Provisions

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H1D5 is the relevant Deemed-to-Satisfy provision in Volume Two for Masonry  

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and this is the connection between the relevant  Australian Standards if you choose those as the  

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Deemed-to-Satisfy solution so that's 3700 or  4773 Parts (1) and (2) or if you choose to  

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use the Deemed-to-Satisfy requirements of  the Housing Provisions it will take it to  

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Part 5.2 that's in H1D5(1)(c) and this is where  the limitations exist if you use the

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Housing Provisions. Noting the first one there is  the maximum wind speed for a design of a  

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building using the Housing Provisions is  not to be more than N3, a wind speed of N3.

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Other limitations relate to the classification of  the site A, S and M that's a site classification  

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that's also similar to that for footings and  slab construction. So the limitations there  

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for wind speed site classification and also  a new requirement that speaks to design for  

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earthquake if you have a design for earthquake  in a house or any residential construction it's  

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limited to the extent that you have to go back  into the Australian Standards 3700 or 4773 for  

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your solution. So in summary if your building  requires earthquake design you have  

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to go back to the relevant Australian Standard  you can't continue to use the Housing Provisions.

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Talking in a bit of detail about Part 5.3 cavity  masonry and we're talking about limitations within  

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the element of cavity masonry as a type of  wall so we've discussed the fact that there  

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are limitations set out broadly in Volume Two  in H1D5, but if you go to cavity masonry  

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in the Housing Provisions because that's the  DtS solution that you choose you'll note that  

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there are also limitations for that particular  element of construction and in this case as  

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an example there's limitations on the height, there's requirements for masonry cross walls  

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that are subject to wind loads to have support  either by a masonry crosswool or steel mullions  

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and stating the obvious in subclause (2) there  cavity masonry must be constructed with two  

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leaves, because that's how we form our cavity, and  each of those leaves needs to be a minimum of

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90 millimeters wide. Also talking about cavities  is a requirement to have a cavity that has a 

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minimum and a maximum dimension, so there's a  limitation there or a value of a minimum

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35 millimeters up to 75 millimeters for a cavity. Noting that any services with the exception of  

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mullions within that cavity need to be clear and  maintain those dimensions. If you do put steel  

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mullions into a cavity you need to make sure that  there is a moisture barrier on the outside Leaf  

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between the inside masonry wall and the external  part of that steel mullion that's in 5.3.2(3)(c).  

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By looking at unreinforced single leaf masonry  it's Part 5.4 of the Housing Provisions 2022  

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this particular figure sets out a requirement for  external walls to be continuously connected to a  

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roof frame. This is not the only Deemed-to-Satisfy  solution but it is the only one contained in the  

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Housing Provisions if you choose a different  method to this that's okay but you would need  

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to get that solution from either of the relevant  Australian Standards that's 3700 or the 4773 suite.

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Also for unreinforced single leaf masonry going to  the tables in particular relating to engaged peers  

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we've changed the format of the tables for NCC  2022 and they look a bit like this now to meet  

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our digital platform we've set them out with  the same information they're just in a new look,

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with new table notes that are relevant to the  information in the table. These tables also are  

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supported by figures which we'll get to in some  slides coming up but importantly to note that  

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there are limitations within these tables, in this  case for engaged peers, the maximum wind speed of  

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N3 noting that for a different thickness of wall  there are different solutions and spacings for  

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the size of engaged peers, depending on what you  choose for whatever design your house will take on.

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A table note worth understanding in this  particular table is for 140 millimeter and  

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190 millimeter thick walls if you read that note it  means you don't necessarily have to have engaged  

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peers. Noting that table notes are normative and  not informative, so if you have a wall with a  

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thickness of 140 millimeters up to 190 millimeters  you don't need to provide engaged peers.

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These diagrams or this diagram rather  shows and supports the information  

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in that table and it simply sets out  maximum dimensions in terms of height,

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spacings between engaged peers and permissible  openings, if any of these dimensions are exceeded  

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it would mean you exceed the dimensions  in that table and if that's the case  

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you would need to go back to the relevant  Australian Standard for the design solution.  

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So looking at Part 5.4 unreinforced single  leaf masonry specifically internal walls now  

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note that in 5.4.3(a) there's a minimum thickness  for an internal wall to be 75 millimeters that's  

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the size of the masonry unit and also there in  (b) we're talking about the connection of these  

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internal walls into the ceiling diaphragm. Just  like we do for timber framing in houses we have a  

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solution that will set out for a minimum thickness  of wall of either 75 millimeters right up to 190.

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A particular height limitation on the height  but importantly those diagrams on the right  

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there are different methods of achieving  connection to the ceiling diaphragm that  

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still allows for differential movement. These  are not the only solutions again if you choose  

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a different solution to these ones you would have  to go back to AS 3700 or 4773 Parts 1 or 2  

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supporting that information those particular  clauses also in Part 5.4 for internal walls other  

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ways of achieving lateral stability is through  return walls shown in this figure. Noting that  

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there are dimensions for wing walls, maximum  spacings of abutting internal walls and also  

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maximum sizes of openings  including articulation joints.

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Overall for Part 5.6 the comparison between 2019  and 2022, that is 2019 Volume Two and 2022 Housing Provisions  

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you'll note that we've added a new  Part 5.6 it's dedicated to masonry components  

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and accessories and the reason we've done  that is to combine all of the accessories

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and components relative to masonry veneer, cavity  masonry, single leaf masonry, isolated piers we've put  

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them all in one place so that we're not repeating  what we're saying in each of those separate parts.

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An important thing to note for masonry components  and accessories and this clause 5.6.6 is a new  

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clause dealing with fixing straps and tie-down  systems. So in summary there are requirements  

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for timber door and window frames a budding  cavity masonry that's in subclause (1) there.

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There are requirements for roof tie down for  external walls that support sheet metal and tile  

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roofs that's subclause (2) and in this subclause  note the requirement for tie-down straps to be  

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at a 1200 millimeter center maximum and also  connected to or adjacent to rafters or trusses.

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Subclause (3) we're talking about  roof framing supporting tiled roofs on  

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single leaf unreinforced masonry  and subclause (4) is talking about  

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roof framing supporting sheet roofs  on single leaf reinforced masonry.

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An important thing to note in the explanatory  information in masonry components and accessories  

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is Illustrated here, I mentioned a moment ago  the 1200 millimeter centers for tie-down straps  

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if you have a length of wall and it contains  an opening and that opening is greater than  

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1200 millimeters wide it still needs to be tied  down but the important thing to note is there  

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are no Deemed-to-Satisfy solutions. So that 1200  millimeter opening or if it's greater than 1200  

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millimeters the solution for tie down across that  opening, as noted in that explanatory information, 

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you'll need to seek a solution separately  because there are no DtS provisions in the  

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Housing Provisions nor are there any in either  of the relevant Australian Standards 3700 or 4773.

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Because we've added single leaf masonry  into the Housing Provisions for 2022 we've  

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got a clause dedicated to weatherproofing  single-leaf masonry should the building you're  

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designing require weatherproofing not necessarily  used for carports or garages using single leaf  

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masonry but if there's a case where you need  to prevent moisture from outside to the inside  

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in a residential part of the building 5.7.6  sets out how you achieve that weatherproofing.