Residential Low Rise Construction : 637693


Q. 1.
Look at the plans provided for Mr & Mrs Walk. Check the
of AS1684.4 to see whether
components of this building can be designed using AS1684.4
Residential timber
-framed construction
with respect to:
Wind classification (assume that, from AS4055, the
site has been determined to be N2)
. Give
a reason for your answer.
. Give a reason for your answer.
Number of storeys of timber framing
. Give a reason for your answer.
Wall height. Give a reason for your answer.
Rafter overhang
. Give a reason for your answer.
Roof types
. Give a reason for your answer.
Q. 2.
Can AS1684 be used to design the floor for this building?
Give your reason(s).
Q. 3.
Referring to
the BCA
, what would be the minimum depth of the concrete
for this
brick veneer (masonry veneer) building on a Class S site
Q. 4. For drainage purposes, what is the minimum height of the slab above the surrounding natural
ground level if the dwelling is to be built in a medium intensity rainfall area
? Where would you f
this information?
5. From the contour lines on the site plan, and the finished floor level shown, and the
requirements as noted in the BCA, will there be any requirement for fill?
(Assume that 150mm of
topsoil will need to be stripped from the area
of the building footprint). Give reason(s) for your
6. What is the allowable bearing pressure of the soil on which the slab edge beams are to be
founded? What is meant by
controlled fill
rolled fill
? What is kPa
a term for, and what does this
allowable bearing pressure
7. Look at the drawings provided of the residential dwelling for Mr & Mrs Walk. With reference
to the BCA
, which of the figures;,,
or would most resemble
a detail
through the external wall at floor level? Give your reasons.
8. With reference to
definitions in the BCA
; w
hat is a DPC and how does it work?
9. With reference to
the definitions in the BCA
; what is
‘ flashing’?
Q. 1
0. Give several examp
les of where flashing would be installed
? Sketch a typical flashing detail
. 12
. What is the minimum cavity allowed in a brick veneer building? Where
would you expect to
find this information?
Fixings are required to all building elements to prevent sections or elements of the building from
being ‘lifted off’ in high winds. ‘Bracing’ is required in the walls and roof (and in the sub
-floor for
framed flooring) to prevent ‘racking’ due to the wind. Section 8.3.2 in AS1684.4 details the
procedure for the design of wall bracing.
Section 9 deals with fixings and tie downs.
Consider that this dwelling will have Type A bracing units (see Clause 1.7f in AS1684.
4) and that a
wind classification of N2 applies.
. What are the
nominal fixing requirements
according to AS1684.4 for:
The bottom plate to the slab
The studs to the bottom plate
The studs to the top plate
. What are the
specific fixing requiremen
if the building is to have a sheet roof:
Bottom plate to slab (truss span 7830mm; fixings at 600
Bottom plate to studs
Studs to top plate
. For common studs spaced at 450mm, notched to allow for services, what size is required for
the studs, given
that it is proposed to use radiata pine, stress grade F5, seasoned timber?
. If MGP10 (machine graded pine) was used, would a smaller size suffice?
Q. 17. Will this size and grade satisfy the requirements for the
end wall studs?
(Consider a roof p
itch of 30 degrees and that a cathedral roof has been designed
for the bedrooms)
If not,
suggest a grade and size that will. S
how your calculations for
the average stud h
eight as per
Figure A6 in A
S1684.4. (note: do not try to size the studs that support the
ridge beam)
Q. 18
. Determine the appropriate house elevation option for each wind direction from Figure 8.3 in


In this assignment, the height of the storey will be taken as 2700mm as it is a single storey residential house.


Grade = MGP10; Grade F5 size = 70*45; Pitch = 30º; Roof type = Cathedral roof; Truss span = 7650mm; Stud spacing = 450mm; Working stud height to ceiling = 2700mm; Average stud height = x.


Since Pitch = 30º, 5 highest heights (aside from ridge beam) are the studs at 450mm, 900mm and 1350mm from the ridge. Therefore heights are:

H1 and H2 = 3375 * tan 30 = 1948.60mm.

H3 and H4 = 2925 * tan 30º = 1688.75mm.

H5 = 2475 * tan 30º = 1429mm.

Average stud height above ceiling = (2(1948.60) + 2(1688.75) + 1429)/5 = 1740.70mm.

Total stud height = 1740.70 + 2700 = 4440.70mm.

The above size and grade will not satisfy the requirements.

Recommend Grade MGP12 size 2/90*45.



East to West = option 2 as the size is greater than 6000mm but less than 12000mm.

North to South = option 3 as the size is greater than 12000mm.



East to West = 11 Type A units required as it is option 2.

North to South = 22 Type A units required as it is option 3.



(a) Two diagonally opposed pairs of timber or metal angle braces = 1800mm

(b) Metal straps – tensioned = 1800mm

(c) Timber and metal angle braces = 1800mm

(e) Diagonal timber wall lining or cladding = 1400mm

(g) Plywood = 900mm

(i) Decorative plywood – nailed = 1400mm

(k) Hardboard = 900mm



Drawing attached below.



(a) Ceiling joist size = 120*35 since joint span 2085mm and is single in this case.

(b) The span of the ceiling joist is 2085mm and is single.

(c) The span of the hanging beam is 4710mm.

(d) Size of the hanging beam is 240*45.

(e) Drawing attached below.



(a) The roof span is 7650mm.

(b) The rafter span is (7650/2)/Cos 30º = 4416.73mm

(c) The under-purlin is required as the length exceeds 2700mm.

(d) Rafter size (grade MGP10) = 90*45.

(e) Rafter overhang = eave width/cos 30º. Since eave width is 450mm,

Overhang = 450/cos 30º

Overhang = 520mm.

(f) Overhang is not compatible with the overhang limit for this size with a standard birdsmouth notch. This is because the limit for this size is 400mm.

(g) For the gable ends of this building, standard engineering principles for roof bracing apply as the pitch exceeds 25º.

(h) If this was a trussed roof, the bracing requirements would be found is AS 4440-2004: Installation of nail-plated timber roof trusses.


Standards Australia, 2010. Residential timber-framed construction: non-cyclonic areas. Standards Australia 2010, AS 1684.4:2010, Standards Australia, Sydney.

Thelandersson, S. and Larsen, H.J. eds., 2003. Timber engineering. John Wiley & Sons.