This video from the 2022 NCC Seminars discusses Part H3 Fire Safety from NCC 2022 Volume Two.
My name is Phil Finnimore from the Australian Building Codes Board
and today I'm going to talk about some changes in NCC 2022 relative to fire safety.
Now the changes being made here haven't fallen from any review of an acceptable construction practice
but rather a discovery of some provisions currently existing
in 2019 that need to be corrected. So what we're talking about is separating walls between two
buildings, that's two Class 1 buildings and in particular the extension of that
fire separating wall as an external wall being the vertical projection of the building below.
So in this particular photo we're looking at a set of town houses.
The building on the left shaded in yellow is separated from the building on the right
through a fire separating wall but you'll note that there's an extension of vertical
projection of that building up to that red overhanging eave. The problem that we're trying
to solve and this is the fact that there's a potential source of fire spread from the roof
in the yellow shaded building into the building on the right there through that red eave area.
Now the problem that we've discovered and are correcting relates to the current provision of
220.127.116.11 allowable encroachments where it says an encroachment is any construction between the
external wall of a building and another building or another boundary or a vertical projection.
Because the wall, because it's saying an encroachment is something that is between
the wall of the building and something else, it doesn't take into consideration where the
projection is beyond that particular line. So the boundary or vertical projection, that dotted line
in the diagram down below, is not caught by this particular provision because it's
extending beyond that it's not captured because it's not between the wall and something else.
Which effectively means you can actually have this particular situation which is not
a desirable situation to have and doesn't necessarily meet the intention of the code.
So what we've done to correct that is added in the Housing Provisions for 2022 a new subclause
in 9.2.9 and that's there in (d), highlighted by that yellow or red outline, and what it's saying
now is an encroachment is any construction that extends beyond the vertical projection of another
building on the same allotment. What that now means is you can't have an allowable and we can't
have an encroachment that extends beyond that because it is a potential source of fire spread.
In 9.2.9 there's another section that we've tidied up as well and if we have a look at this one
subclause (1)(c) and encroachment is any construction between the external wall of the building and
the vertical projection of the external wall of another building on the same allotment. Now that's
the outcome we're looking for but if we have a look at this particular photo and go back to
subclause (e) and those same provisions in 2019 you'll see that this particular overhang is not
permitted and it's not permitted because in (e) it's saying the encroachments allowed between
the external wall of a building and the vertical projection of an adjoining building, which is that
red dotted line up the middle, is limited to non-combustible fascias, gutters and down pipes
but this situation with that eave overhang is much safer than one that we showed before where
the red overhang overhanging eave was above that townhouse that was shaded in yellow.
So the code is saying you can't do this but it's significantly safer than what we've currently got
so what we've done is changed in the Housing Provisions for 2022 subclause (5) in the allowable
encroachment provisions to say encroachments allowed to project beyond the vertical projection
of another building are non-combustible fascias, gutters and downpipes. So you can have an eave
overhang in this particular situation, you're still subject to the limitations of how close
that can go to the vertical projection but if there are any encroachments hanging over that
particular red dotted line they can only be non-combustible fascias, gutters and downpipes.