This video from the 2022 NCC Seminars discusses Part 5.4 Unreinforced single leaf masonry from the NCC 2022 Housing Provisions.
My name is Phil Finnimore, with the Australian Building Codes Board and today I'm going to talk to you about masonry
construction and the details within Volume Two and the Housing Provisions of NCC 2022.
H1D5 of Volume Two sets out the Deemed-to-Satisfy pathways shown in this slide. On the right hand
side is AS 3700 or the 4773.1 and .2 suite of standards. This is known in 2019 as an acceptable
construction manual simply referenced in the Housing Provisions for 2022 as reference documents.
If you choose this path they're the relevant standards if you don't choose this path you can go
to Part 5.4, that's on the left hand side of this slide, which are the Deemed-to-Satisfy requirements
set out in the Housing Provisions for 2022. So to be clear for masonry there's a choice a complete
choice between a referenced Australian Standard 3700 or 4773 or Part 5.4 of the Housing Provisions.
Comparisons between 2019 Volume Two and the Housing Provisions
which is where the Deemed-to-Satisfy requirements are for masonry construction
on the left Part 3.3 2019 starts at 3.3.1 go through go through to Part 3.3.6
unreinforced masonry all the way through to ice isolated masonry repairs.
What we've changed for NCC 2022 is the addition of cavity masonry Deemed-to-Satisfy requirements
and unreinforced single leaf masonry requirements. These are in addition to those of 2019 and I'll
talk about some details of those and how Volume Two connects those to the Housing Provisions
H1D5 is the relevant Deemed-to-Satisfy provision in Volume Two for Masonry
and this is the connection between the relevant Australian Standards if you choose those as the
Deemed-to-Satisfy solution so that's 3700 or 4773 Parts (1) and (2) or if you choose to
use the Deemed-to-Satisfy requirements of the Housing Provisions it will take it to
Part 5.2 that's in H1D5(1)(c) and this is where the limitations exist if you use the
Housing Provisions. Noting the first one there is the maximum wind speed for a design of a
building using the Housing Provisions is not to be more than N3, a wind speed of N3.
Other limitations relate to the classification of the site A, S and M that's a site classification
that's also similar to that for footings and slab construction. So the limitations there
for wind speed site classification and also a new requirement that speaks to design for
earthquake if you have a design for earthquake in a house or any residential construction it's
limited to the extent that you have to go back into the Australian Standards 3700 or 4773 for
your solution. So in summary if your building requires earthquake design you have
to go back to the relevant Australian Standard you can't continue to use the Housing Provisions.
Talking in a bit of detail about Part 5.3 cavity masonry and we're talking about limitations within
the element of cavity masonry as a type of wall so we've discussed the fact that there
are limitations set out broadly in Volume Two in H1D5, but if you go to cavity masonry
in the Housing Provisions because that's the DtS solution that you choose you'll note that
there are also limitations for that particular element of construction and in this case as
an example there's limitations on the height, there's requirements for masonry cross walls
that are subject to wind loads to have support either by a masonry crosswool or steel mullions
and stating the obvious in subclause (2) there cavity masonry must be constructed with two
leaves, because that's how we form our cavity, and each of those leaves needs to be a minimum of
90 millimeters wide. Also talking about cavities is a requirement to have a cavity that has a
minimum and a maximum dimension, so there's a limitation there or a value of a minimum
35 millimeters up to 75 millimeters for a cavity. Noting that any services with the exception of
mullions within that cavity need to be clear and maintain those dimensions. If you do put steel
mullions into a cavity you need to make sure that there is a moisture barrier on the outside Leaf
between the inside masonry wall and the external part of that steel mullion that's in 5.3.2(3)(c).
By looking at unreinforced single leaf masonry it's Part 5.4 of the Housing Provisions 2022
this particular figure sets out a requirement for external walls to be continuously connected to a
roof frame. This is not the only Deemed-to-Satisfy solution but it is the only one contained in the
Housing Provisions if you choose a different method to this that's okay but you would need
to get that solution from either of the relevant Australian Standards that's 3700 or the 4773 suite.
Also for unreinforced single leaf masonry going to the tables in particular relating to engaged peers
we've changed the format of the tables for NCC 2022 and they look a bit like this now to meet
our digital platform we've set them out with the same information they're just in a new look,
with new table notes that are relevant to the information in the table. These tables also are
supported by figures which we'll get to in some slides coming up but importantly to note that
there are limitations within these tables, in this case for engaged peers, the maximum wind speed of
N3 noting that for a different thickness of wall there are different solutions and spacings for
the size of engaged peers, depending on what you choose for whatever design your house will take on.
A table note worth understanding in this particular table is for 140 millimeter and
190 millimeter thick walls if you read that note it means you don't necessarily have to have engaged
peers. Noting that table notes are normative and not informative, so if you have a wall with a
thickness of 140 millimeters up to 190 millimeters you don't need to provide engaged peers.
These diagrams or this diagram rather shows and supports the information
in that table and it simply sets out maximum dimensions in terms of height,
spacings between engaged peers and permissible openings, if any of these dimensions are exceeded
it would mean you exceed the dimensions in that table and if that's the case
you would need to go back to the relevant Australian Standard for the design solution.
So looking at Part 5.4 unreinforced single leaf masonry specifically internal walls now
note that in 5.4.3(a) there's a minimum thickness for an internal wall to be 75 millimeters that's
the size of the masonry unit and also there in (b) we're talking about the connection of these
internal walls into the ceiling diaphragm. Just like we do for timber framing in houses we have a
solution that will set out for a minimum thickness of wall of either 75 millimeters right up to 190.
A particular height limitation on the height but importantly those diagrams on the right
there are different methods of achieving connection to the ceiling diaphragm that
still allows for differential movement. These are not the only solutions again if you choose
a different solution to these ones you would have to go back to AS 3700 or 4773 Parts 1 or 2
supporting that information those particular clauses also in Part 5.4 for internal walls other
ways of achieving lateral stability is through return walls shown in this figure. Noting that
there are dimensions for wing walls, maximum spacings of abutting internal walls and also
maximum sizes of openings including articulation joints.
Overall for Part 5.6 the comparison between 2019 and 2022, that is 2019 Volume Two and 2022 Housing Provisions
you'll note that we've added a new Part 5.6 it's dedicated to masonry components
and accessories and the reason we've done that is to combine all of the accessories
and components relative to masonry veneer, cavity masonry, single leaf masonry, isolated piers we've put
them all in one place so that we're not repeating what we're saying in each of those separate parts.
An important thing to note for masonry components and accessories and this clause 5.6.6 is a new
clause dealing with fixing straps and tie-down systems. So in summary there are requirements
for timber door and window frames a budding cavity masonry that's in subclause (1) there.
There are requirements for roof tie down for external walls that support sheet metal and tile
roofs that's subclause (2) and in this subclause note the requirement for tie-down straps to be
at a 1200 millimeter center maximum and also connected to or adjacent to rafters or trusses.
Subclause (3) we're talking about roof framing supporting tiled roofs on
single leaf unreinforced masonry and subclause (4) is talking about
roof framing supporting sheet roofs on single leaf reinforced masonry.
An important thing to note in the explanatory information in masonry components and accessories
is Illustrated here, I mentioned a moment ago the 1200 millimeter centers for tie-down straps
if you have a length of wall and it contains an opening and that opening is greater than
1200 millimeters wide it still needs to be tied down but the important thing to note is there
are no Deemed-to-Satisfy solutions. So that 1200 millimeter opening or if it's greater than 1200
millimeters the solution for tie down across that opening, as noted in that explanatory information,
you'll need to seek a solution separately because there are no DtS provisions in the
Housing Provisions nor are there any in either of the relevant Australian Standards 3700 or 4773.
Because we've added single leaf masonry into the Housing Provisions for 2022 we've
got a clause dedicated to weatherproofing single-leaf masonry should the building you're
designing require weatherproofing not necessarily used for carports or garages using single leaf
masonry but if there's a case where you need to prevent moisture from outside to the inside
in a residential part of the building 5.7.6 sets out how you achieve that weatherproofing.