Construction IV: Timber Frame Design & AS1684.4 Compliance Analysis

This assignment provides a detailed solution to a construction problem involving timber framing design for the Walk Residence, based on AS1684.4 standards and Building Code of Australia (BCA) compliance. It assesses various aspects such as wind classification suitability, plan layout considerations, storey limitations, width and height restrictions, rafter overhangs, and roof types. The solution covers concrete slab requirements, drainage considerations, and the use of damp-proof courses. It also addresses the sizing of timber members, fixing requirements for wall framing, and bracing requirements for different wall orientations, including wind bracing. Furthermore, the assignment examines roof framing, including rafter sizes, spans, and overhang calculations, ensuring all elements comply with AS1684.4 and BCA guidelines. The document includes references to relevant literature on durability design for wood construction and timber engineering.

CONSTRUCTION IV IN BUILDING & CONSTRUCTION
[Author Name(s), First M. Last, Omit Titles and Degrees]
[Institutional Affiliation(s)]

Floor framing - AS1684.4
Q
no Answer Reason or Explanation
1i Suitable The building is to be built in a city square whose perimeter has an
estimate of over 250,000 meters squared of open field.
ii Suitable The plan layout is partly L-shaped and rectangular which is within
the physical 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 16m which is the maximum
v Suitable The wall height is within the limits of 3000mm
vi Suitable The hanging rafter is within the standard 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 equipment
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 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 attachment.
8
A DPC is a barrier that prevents
moisture from penetrating through a
structure by capillary action through
the rising damp phenomenon.
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
11 Size of floor Framing Members - identify the location of timber stumps, bearer, joists and
the ledger on the plan below.

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 Unseasoned
F11
Joist Unseasoned
Existing brick
veneer house
3800 mm
9200 mm

F11
Decking
You will need
to do a little
research (not in
AS1684)
Australian
Spotted gum 175 x 50mm
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 loads.
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
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 continuos span
c) Size of hanging beam 1840mm
d) 190 x 45

e)

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 strength.
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 underpurlin.
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

References
Foliente, G. C., Leicester, R. H., Wang, C. H., Mackenzie, C., & Cole, I. (2002). Durability
design for wood construction. Forest Products Journal, 52(1), 10-19.
Leicester, R. H. (2001). Engineered durability for timber construction. Progress in Structural
Engineering and Materials, 3(3), 216-227.
Thelandersson, S., & Larsen, H. J. (Eds.). (2003). Timber engineering. John Wiley & Sons.