Analysis of Residential Timber-Framed Construction Using AS1684.4

This assignment focuses on analyzing a residential timber-framed construction project for Mr. & Mrs. Walk, using AS1684.4, the BCA (Building Code of Australia), and provided house plans. It assesses the applicability of AS1684.4 concerning wind classification, plan layout, number of stories, width, wall height, rafter overhang, and roof types. The solution includes determining minimum concrete slab depth, analyzing floor framing (timber stumps, bearers, joists, ledger), sizing framing members based on span and spacing, and detailing wall framing requirements including nominal and specific fixing. Furthermore, it covers bracing requirements, roof framing calculations, and considerations for roof overhangs, ensuring compliance with relevant building codes and standards. The document also includes a bibliography with cited academic resources.

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RESIDENTIAL TIMBER – FRAMED CONSTRUCTION
Student’s Name
Course Name
Date

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Floor framing - AS1684.4
Q
No Answer Reason or Explanation
1i Suitable The house is to be built in a city square whose perimeter has an
estimate of over 250,000 m2 of an open field.
Ii Suitable The plan layout is partly L-shaped and rectangular which is
within the flexible limits for timber-framed construction
Iii Single and two storey Depending on the timber strength, it can only support the
maximum load of a two story building.
Iv Suitable The width is less than 16000mm which is maximum
V Suitable The wall height is within the maximum range of 3000mm
Vi Suitable The hanging rafter is within the required limits
Vii Suitable Roof pitch is 30⁰ which is within the maximum limit of 35⁰
2 Yes
The site has such topography that is able to support the structure,
the floor span is also within the maximum span for timber floor
construction, hence within the deflection limits
3 450mm
4 300mm. Reference from the BCA
5 No requirement for filling Suspended floor can be employed in the construction, hence pad
foundation can be used for construction.
6 50kPa,
Controlled fill is where a tested
material imported to the site or
found on site is placed in layers of
150mm, the moisture content is
regulated by adding water using a
compaction equipment1.
A rolled fill is an embankment of
the earth or rocks where the
material is placed in layers and
compacted using rolling
equipment. KPa is a unit for
1 Allen, Edward, Rob Thallon, and Alexander C. Schreyer. Fundamentals of residential construction. John Wiley &
Sons, 2017.

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measuring pressure. Allowable
bearing pressure is the maximum
stress that can be applied on a
foundation such that it is able to
withstand the shear failures.
7 Diagrams 3.2.5.4
In compliance with the BCA, an external wall should be non-
combustible and if made of a combustible material then it should
be in accordance with certain fire hazard properties so as to be
treated as an attachment2.
8
A DPC is a barrier that prevents
moisture from penetrating
through a structure by capillary
action through the rising damp
phenomenon3.
9
Thin material pieces of
impervious materials that are
installed to prevent water passage
through and into a structure
10 Windows, vent pipes, roofs walls,
door openings
2 Dakin, Anthony. "Investigation of the suitability of finger jointed structural timber for use in nail plated roof
trusses." (2011), 240.
3 Aktaş, Yasemin Didem, Uğurhan Akyüz, Ahmet Türer, Barış Erdil, and Neriman Şahin Güçhan. "Seismic resistance
evaluation of traditional Ottoman timber-frame Hımış houses: frame loadings and material tests." Earthquake
Spectra 30, no. 4 (2014), 1721.

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Typical flashing detail
11 Size of floor Framing Members - identify the location of timber stumps, bearer, joists
and the ledger on the plan below.

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Q11 continued… Size the members.
AS1684 table
used
Timber
stress
grade
Span
mm
Spacing
mm
Single or
continuous
Span used for
sizing?
Size
(mm x mm)
Post
(note:
footing
type 2)
F11 1400mm 50 x 100mm
Bearers
Unseasone
d
F11
Joist
Unseasone
d
F11
Decking You will need
to do a little
Australian
Spotted
175 x 50mm
Existing brick
veneer house
3800 mm
9200 mm

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research (not
in AS1684) gum
Wall framing - AS1684.4
Q.
No. Answer Reason or Explanation
12 40 mm. Reference
from the BCA.
13 nominal fixing requirements according to AS1684.4
a The nominal fixing requirement of the bottom plate to slab is 1200 mm crs
b
The nominal fixing requirement of the studs to the bottom plate is 600 mm crs
c The nominal requirement of the studs to the top plate is 450mm crs
14 specific fixing requirements if the building is to have a sheet roof:
a Bottom plate to slab is 80 mm
b Bottom plate to studs is 120 mm
c Stud to top plate is 90mm
15 100 x 75 mm
16 A small size
would not be
suffice
MPG10 is the smallest grade of underpin, therefore, this means that
it would not be able to fully support the loads4.
17 MPG12 T2 H2
The garage is located on the west side of the building. Therefore, this
means that the wall on this side require materials with high strength
in order to support the load bearing of the roof structure.
18
East-west
direction
Reduce the number of openings or fenestration
North-south
direction Should have the maximum number of openings such as windows
19 None The frames would be in a position to resist the gravity loads
together
None The frames would be in a position to resist the gravity loads
together
4 Dias, A. M. P. G., Jonathan Skinner, Keith Crews, and Thomas Tannert. "Timber-concrete-composites increasing
the use of timber in construction." European Journal of Wood and Wood Products 74, no. 3 (2016), 445..

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20a
Two diagonally
opposed pairs of
timber or metal
angle braces
3600mm
b Metal straps -
tensioned
3600mm
c Timber and metal
angle braces
3000mm
d Diagonal timber
wall lining or
cladding
2700mm
e Plywood 353mm
f Decorative
plywood - nailed
2600mm
g Hardboard 1219mm
21
Note: every student will have a different layout. Ensure they have sufficient bracing and
comply with the Rules and allowances of Clause 8.3.2.3
See suggested layout provided. Type A 14 units East-West; 22 units North-South
Ensure that wind bracing is installed in walls parallel to the wind direction
Roof framing - AS1684.4
22a) 47 x 220
b) 5000mm, the span should be a continuous span

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c) Size of hanging beam 1840mm
d) 190 x 45
e)

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23a) 1600mm The roof overlaps from the external wall by a
minimum of 600mm
b) 2600mm As of the size of the rafter used which is 170 x 45
c) Underpurlin is required
Since it’s a continuous roof span, the roof will need
support from the underpurlin at regular spacing in
order to achieve the required design strength5.
d) 140 x 50
There would be an additional support introduced to
strengthen the roof skeleton structure, hence there
would be need for smaller rafters since the support
required has been supplemented by the underpurlin6.
e)
Eave width of 450mm
Roof pitch is 30 degree
Trigonometry
Cosine (x) =Adjacent/hypotenuse
X will be the roof pitch
Adjacent is the eave =450mm
Hypotenuse is the overhanging
rafter
Cosine 30 deg = 450/hypotenuse
Hypotenuse = 450/cosine 30 deg
=519.6152
Rafter overhang = 520mm
To determine the rafter overhang, trigonometry has
been employed to calculate the overhang rafter
f) The overhang is compatible with
the standard birds mouth notch
The span of the overhang is within the 2 x 6 range of
the birds mouth notch
g) Roof truss bracing For stabilizing the gable ends
h) BCA document
5 Dizhur, Dmytro, Lisa Moon, and Jason Ingham. "Observed performance of residential masonry veneer
construction in the 2010/2011 Canterbury earthquake sequence." Earthquake Spectra 29, no. 4 (2013), 1260.
6 Leicester, Robert H., Chi-Hsiang Wang, Minh N. Nguyen, and Colin E. MacKenzie. "Design of exposed timber
structures." Australian Journal of Structural Engineering 9, no. 3 (2009): 220.

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Bibliography
Allen, Edward, Rob Thallon, and Alexander C. Schreyer. Fundamentals of residential
construction. John Wiley & Sons, 2017.
Aktaş, Yasemin Didem, Uğurhan Akyüz, Ahmet Türer, Barış Erdil, and Neriman Şahin Güçhan.
"Seismic resistance evaluation of traditional Ottoman timber-frame Hımış houses: frame
loadings and material tests." Earthquake Spectra 30, no. 4 (2014): 1711-1732.
Dakin, Anthony. "Investigation of the suitability of finger jointed structural timber for use in nail
plated roof trusses." (2011).
Dias, A. M. P. G., Jonathan Skinner, Keith Crews, and Thomas Tannert. "Timber-concrete-
composites increasing the use of timber in construction." European Journal of Wood and
Wood Products 74, no. 3 (2016): 443-451.
Dizhur, Dmytro, Lisa Moon, and Jason Ingham. "Observed performance of residential masonry
veneer construction in the 2010/2011 Canterbury earthquake sequence." Earthquake
Spectra 29, no. 4 (2013): 1255-1274.
Iddon, Christopher R., and Steven K. Firth. "Embodied and operational energy for new-build
housing: a case study of construction methods in the UK." Energy and Buildings 67
(2013): 479-488.
Kremer, P. D., and M. A. Symmons. "Mass timber construction as an alternative to concrete and
steel in the Australia building industry: a PESTEL evaluation of the
potential." International Wood Products Journal 6, no. 3 (2015): 138-147.

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Leicester, Robert H., Chi-Hsiang Wang, Minh N. Nguyen, and Colin E. MacKenzie. "Design of
exposed timber structures." Australian Journal of Structural Engineering 9, no. 3 (2009):
217-224.
Mix, Dustin, Tracy Kijewski-Correa, and Alexandros A. Taflanidis. "Assessment of residential
housing in Leogane, Haiti, and identification of needs for rebuilding after the January
2010 earthquake." Earthquake Spectra 27, no. S1 (2011): S299-S322.
McLeod, Virginia. Detail in contemporary timber architecture. Laurence King Publishing, 2010
Pearson, Cecil, and Klaus Helms. "Indigenous entrepreneurship in timber furniture
manufacturing: The Gumatj venture in northern Australia." Information Management and
Business Review 2, no. 1 (2011): 1-11.
O’Brien, Darryl. "Know the code." Building Connection Winter 2018 (2018): 56.
.