AS1684_Using_Span_Tables_7_14

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AS 1684 Teaching Guide
TIMBER FRAMING
USING AS 1684.2 SPAN TABLES
AS
AS1684-2010
1684-2010
Residential
Residentialtimber-framed
timber-framedconstruction
construction
• Go to www.education.WoodSolutions.com.au for up to date
teaching resources including an annotated copy of the standard.
• This powerpoint presentation is part of a series that has been
revised to reflect the requirements of AS 1684 Parts 2 & 3 – 2010
Edition.
• Some major changes to this edition include amendments to wall
nogging requirements, inclusion of ring beam systems and an
Appendix of building practices for engineered wood products
(EWPs).
• The MGP span tables provided with the Standard have also been
amended.
AS 1684
theTIMBER-FRAMED
timber framing
standard
RESIDENTIAL
CONSTRUCTION
Currently you should be using the 2010 Edition.
AS 1684
TIMBER-FRAMING STANDARD
Provides the building industry with procedures that can be
used to determine building practice to design or check
Construction details, determine member sizes and bracing
and fixing requirements for timber framed construction in
Non-Cyclonic areas (N1 – N4).
AS 1684
AS 1684.2
– CD
TIMBER-FRAMING
STANDARD
Span Tables
Contains a CD of Span Tables (45 sets in all) for wind zones
N1 - N4 for the following timber stress grades:
Unseasoned Softwood:
F5, F7
Seasoned Softwood:
F5, F7, F8
MGP10, MGP12, MGP15
Unseasoned Hardwood:
F8, F11, F14, F17
Seasoned Hardwood:
F14, F17, F27
AS 1684
TIMBER-FRAMING STANDARD
Each set of Span Tables contains 53 separate design tables
AS 1684
TIMBER-FRAMING STANDARD
Using AS 1684 you should be able to design or check
virtually every member in a building constructed using
timber framing.
AS 1684
TIMBER-FRAMED CONSTRUCTION
Ridge beam
Battens
Rafters
Hanging beams
Ceiling
Ceiling battens
First floor wall frames
Roofing
External cladding
Floor joists
Flooring
Ceiling battens
Wall frame
Wall stud
Floor joists
Stumps or piles
Lintel
Internal cladding
Flooring
Bearers
AS 1684
Scope and Limitations
WHERE CAN AS1684 BE USED?
AS 1684
Physical Limitations -
W
16.0 m max.
Plan:
Rectangular, square or “L”-shaped
Storeys: Single and two storey construction
Pitch: 35o max. roof pitch
Width: 16m max. (between the “pitching points” of the
roof, i.e. excluding eaves)
W
16.0 m max.
AS 1684
Width
Physical Limitations - Width
The geometric limits of the span tables often will limit
these widths.
Pitching Point
of main roof.
Pitching Point
of main roof.
Pitching Point
of verandah or
patio roof.
Pitching Point
of garage roof.
Garage
16.0 m max.
Main house
16.0 m max.
Verandah
or Patio
16.0 m max.
AS 1684
Wall Height
Physical Limitations – Wall Height
The maximum wall height shall be 3000 mm (floor to
ceiling) as measured at common external walls
(i.e. not gable or skillion ends).
AS 1684
Design Forces on Buildings
Physical Limitations – Design Forces on Buildings
AS1684 can be used to design for Gravity Loads (dead &
live) and wind loads.
Suction (uplift)
Construction loads (people, materials)
DEAD LOAD (structure)
LIVE LOADS (people, furniture etc.)
Wind
Internal
pressure
Suction
DEAD LOAD (structure)
(a) Gravity loads
(b) Wind loads
AS 1684
Wind Classification Wind
Classification
Non-Cyclonic Regions A & B only
N1 - W28N
100km/h gust
N2 - W33N
120km/h gust
N3 - W41N
150km/h gust
N4 - W50N
180km/h gust
AS 1684
Wind Classification Wind
Classification
Wind Classification is dependent on :
 Building height
 Geographic (or wind) region (A for Victoria)
 Terrain category (roughness of terrain)
 Shielding classification (effect of surrounding objects)
 Topographic classification (effect of hills, ridges, etc.)
AS 1684
Wind Classification – Simple References
Geographic Region A
Site Location
Suburban site
Not within two rows of:
• City or Town perimeter (as estimated 5 years hence)
• Open areas larger than 250,000 m2
Top ⅓ of hill
or ridge
Below top ⅓ of
hill or ridge
N2
N1
N3
N2
Less than 250m from:
• the sea
• open water wider than 250m
Within two rows of:
• City or Town perimeter (as estimated 5 years hence)
• Open areas larger than 250,000 m2
Rural areas
AS 1684
Using Span Tables
Design fundamentals & basic terminology
Roof framing
Wall framing
Floor framing
(Click on arrow to move to section required)
AS 1684
Using Span Tables
DESIGN FUNDAMENTALS
&
BASIC TERMINOLOGY
AS 1684 SPAN TABLES
Design Fundamentals – Load Path
Design Fundamentals
You build from the Bottom up.
But you design from the Roof
down because loads from above
can impact on members below.
So start with the roof and work
down to the ground level.
AS 1684 SPAN TABLES
Design Fundamentals – Load Path
Understanding the concept of a ‘load path’ is critical.
Loads need to be supported down the building to the
ground.
Roof
Load
Indirect Load path
due to cantilever
Ground level
AS 1684 SPAN TABLES
Design Fundamentals – Load Path
As a general rule it is necessary to
increase the timber member size when:
 Load increases (a function of dead,
live, wind loads).
 Span increases (a function of load
paths across openings).
 Indirect load paths occur (e.g.
cantilevers and offsets).
It is possible to decrease timber member
size when:
 Sharing loads across many members.
 Using members with higher stress
grades.
Roof
Load
Indirect Load path
due to cantilever
Ground level
AS 1684 SPAN TABLES
Loads distributed
Design Fundamentals – Load Distribution
Loads are distributed equally between Points of Support.
MEMBER X
A
B
Of the total load on Member X one half (2000 mm) will be
supported by the beam or wall at “A” and the other half
(2000 mm) will be supported by the beam or
wall at “B”.
AS 1684 SPAN TABLES
Design Fundamentals – Load Distribution
If Member X is supported at three or more points it is
assumed that half the load carried by the spans either
side of supports will be distributed equally.
MEMBER X
AA
BB
Beam A will carry 1000 mm of load
Beam B will carry 3000 mm
(1000 mm plus 2000 mm on other side)
Beam C will carry 2000 mm
CC
AS 1684 SPANTerminology
TABLES
- Span and Spacing
Terminology – Span
Span is the “face-to-face” distance between points
capable of giving full support to structural members or
assemblies.
Joist Span (between internal faces of
these support members).
Bearers and Floor Joists
AS 1684 SPAN TABLES
Terminology – Single Span
The span of a member supported at or near both ends
with no immediate supports.
Si ngl e span
This includes the case where members are partially cut
through over intermediate supports to remove spring.
Saw cut
Joint or lap
Single span
Single span
AS 1684 SPAN TABLES
Terminology – Continuous Span
The term applied to members supported at or near both
ends and at one or more intermediate points such that no
span is greater than twice another.
Continuous
span
Continuous
span
NOTE: The design span is the average span
unless one span is more than 10% longer than
another in which case the design span is the
longest span.
AS 1684 SPAN TABLES
Example: Continuous Span
Continuous Span Example
6000 mm
1/3 (2000 mm)
1/3 (2000 mm)
1/3 (2000 mm)
The center support
must be wholly within
the middle third.
Span 1 (2000 mm)
75 mm
Span 2 (3925 mm)
75 mm
75 mm
Span 2 is not to be greater than twice Span 1.
This span is used to determine the size using
the Continuous Span tables.
AS 1684 SPAN TABLES
Terminology – Rafter Span and Overhang
Terminology - Rafter Span and Overhang
Rafter spans are measured as the distance between points
of support along the length of the rafter and NOT as the
horizontal projection of this distance.
pa
s
er
t
f
Ra
Ov
e
n
r ha
n
g
Rafter
AS 1684 SPANTerminology
TABLES
- Span and Spacing
Design Fundamentals – Spacing
Spacing is the centre-to-centre distance between
structural members unless indicated otherwise.
Joist Spacing
(Centreline-to-Centreline)
Bearers and
Floor joists
Bearer Spacing
(Centreline-to-Centreline).
AS 1684 SPAN TABLES
Terminology – Wall Construction
Terminology – Wall Construction
Loadbearing wall
A wall that supports roof loads, floor loads or both.
Non-Loadbearing internal wall
A wall that does not support roof or floor loads but may
support ceiling loads and act as a bracing wall.
The main consideration for a non-loadbearing internal wall
is its stiffness (i.e. resistance to movement from someone
leaning on the wall, doors slamming shut etc.).
AS 1684 SPAN TABLES
Terminology – Roof Construction
Terminology – Roof Construction
Coupled Roof - rafters are tied together by ceiling joists so
that they cannot spread.
Ridge board
Rafter
Ceiling joist
Rafters & Ceiling Joist must be
fixed together at the pitching points
Ridge board
Rafter
Ceiling joist
(Collar Tie)
This method of roof construction
is not covered by AS1684
otherwise there is nothing to stop
the walls from spreading
and the roof from collapsing
AS 1684 SPAN TABLES
Terminology – Roof Construction
Non-coupled roof - a pitched roof that is not a coupled
roof. It includes cathedral roofs and roofs constructed
using ridge and intermediate beams
Such roofs rely on ridge and intermediate beams to
support the centre of the roof. These ridge and
intermediate beams are supported by walls and/or posts
at either end.
Ridge Beam
Rafter
Intermediate Beam
AS 1684 SPAN TABLES
Using Span Tables
ROOF FRAMING
AS 1684 SPAN TABLES
Roof Framing – Typical Basic Roof Shapes
The “footprint” of a building generally consists of a
rectangular block or multiple blocks joined together.
Roof shapes are made to cover the footprint while also
providing sloping planes able to shed water.
Hip
Gable
(Cathedral or flat ceiling)
Skillion
Hip and valley
Dutch Hip
(or Dutch Gable)
AS 1684 SPAN TABLES
Roof Framing – Typical Members
Rafter
Ridgeboard
Collar tie
Top plate
Top plate
Underpurlin
Strut
Ceiling joist
Strutting
beam
Strut
AS 1684 SPAN TABLES
Roof Framing - Transferring loads to Pitched Roof
1. Roofing material takes live/dead/wind
loads and transfers
them to the Battens.
2. Battens - takes
roofing loads
and transfers
them to the
Rafters/Trusses.
3. Rafters – take
batten loads and
transfers them to
the support
structure below
e.g. walls.
Support
wall
AS 1684 SPAN TABLES
Roof Framing – Batten Design
Typical Process
Step 1: Determine the wind classification to factor in wind
loads (e.g. assume non-cyclonic winds N1 or N2)
Step 2: Determine type of roof (e.g. tiled or sheet.)
Step 3: Determine batten spacing – typically 330 mm for
tiles, or 450, 600, 900, 1200 mm sheet
Step 4: Determine batten span – this will be the supporting
rafter spacing.
Batten
Batten
Span
Spacing
AS 1684 SPAN TABLES
Roof Framing – Batten Design
Step 5: Look up relevant Batten Span Table (i.e. noncyclonic winds N1 and N2) in AS1684 Vol. 2.
Step 6: Choose a table reflecting preferred stress grade.
Step 7: Select column in the table for the previous batten
“spacing and span” assumptions.
AS 1684 SPAN TABLES
Roof Framing – Batten Size Example
Inputs required
 Wind Classification
 Timber Stress Grade
 Roof Type
 Batten Spacing
 Batten Span
= N2
= F8
= Steel Sheet (20 kg/m2)
= 900 mm
= 900 mm
AS 1684 SPAN TABLES
Roof Framing – Batten Size Example
2006
Simplify
table
Wind Classification N2
Roof Type - Steel Sheet (20 kg/m2)
Timber Stress Grade F8
Batten Spacing = 900 mm
Batten Span
= 900 mm
A 38 x 75 mm F8 Batten Is
adequate
AS 1684 SPAN TABLES
Rafter Design - Cathedral Roof Scenario
Step 1: Determine the wind classification to
factor in wind loads. For this example
assume non-cyclonic winds N1 or N2.
Step 2: Determine dead/live loads on rafters .
For this example assume loads are as
for a tiled roof with battens (e.g.
60kgs/m2)
Step 3: Determine the rafter span. For the
example assume a 2100 mm single
rafter span.
Step 4: Determine the rafter overhang which
creates a cantilever span adding extra
load. For the example assume a 500
mm overhang.
Step 5: Determine the rafter spacing as this
determines how much roof loads are
shared between rafters. For the
example assume a 600 mm spacing .
Ridge beam
Rafter
Spacing
AS 1684 SPAN TABLES
Rafter Design - Cathedral Roof Scenario
Step 6 Look up AS1684 Vol 2
Step 7 Choose table reflecting
preferred stress grade
Step 8 Determine which column
in table to select using the
previous “rafter spacing”
and “single span”
assumptions.
Step 9 Go down the column
until reaching assumed
2100 mm rafter span
and 500 mm overhang
Step 10 Check the spans work
with assumed roof load
of 60kgs/m2
Step 11 Read off rafter size –
90x45mm
AS 1684 SPAN TABLES
Rafter Design - Cathedral Roof Scenario
Inputs required
 Wind Classification
 Stress Grade
 Rafter Spacing
 Rafter Span
 Single or Continuous Span
 Roof Mass (Sheet or Tile)
= N2
= F8
= 900 mm
= 2200 mm
= Single
= Steel Sheet (20 kg/m2)
Determine Rafter Size
2006
Maximum Rafter or Purlin Span & Overhang (mm)
Simplify table
A 100 x 50mm F8
rafter
is adequate
At least
2200mm
Inputs required
• Wind Classification
• Stress Grade
• Single or Continuous Span
• Rafter Spacing
• Rafter Span
• Roof Mass (Sheet or Tile)
= N2
= F8
= Single
= 900 mm
= 2200 mm
= Steel Sheet
(20 kg/m2)
AS 1684 SPAN TABLES
Ceiling Joist Design
Ceiling Joist Design
Ridge board
Rafter
Ceiling Joist
Design variables
• Timber Stress Grade
• Ceiling Joist Spacing
• Ceiling Joist Span
• Single or Continuous Span
AS 1684 SPAN TABLES
Ceiling Joist Design
Ceiling Joist Design Example
Inputs required
 Wind Classification
 Stress Grade
 Overbatten
 Single or Continuous Span
 Joist Spacing
 Ceiling Joist Span
= N2
= F17
= No
= Single
= 450 mm
= 3600 mm
Ceiling Joist Size
2006
Simplify table
Inputs required
At least
3600mm
A 120 x 45mm F17
ceiling joist is adequate
•
•
•
•
•
•
Wind Classification
= N2
Stress Grade
Overbatten
Single or Continuous Span
Joist Spacing
Ceiling Joist Span
= F17
= No
= Single
= 450 mm
= 3600mm
AS 1684 Span Tables
Ridge board
Other Members And Components - Ridge board
Some members do not have to be designed using span
tables. They are simply called up or calculated based on
members framing into them.
Member
Ridgeboards
Hip rafters
Application
Minimum size (mm)
Unstrutted ridge in coupled roof
Depth not less than length of the rafter
plumb cut  19 thick
Strutted ridge in coupled roof with strut
spacing not greater than 1800 mm
Depth not less than length of the rafter
plumb cut  19 thick
Strutted ridge in coupled roof with strut
spacing greater than 1800 to 2300 mm
Depth not less than length of the rafter
plumb cut  35 thick
Stress grade F11/MGP15 minimum and
no less than rafter stress grade
50 greater in depth than rafters
 19 thick (seasoned) or 25 thick
(unseasoned)
Stress grades less than F11/MGP15
50 greater in depth than rafters
 min. thickness as for rafters
Valley rafters
Minimum stress grade, as for rafters
50 greater in depth than rafters
with thickness as for rafter (min. 35)
Valley boards
See Note
Roof struts
(sheet roof)
19 min. thick  width to support valley
gutter
Struts to 1500 mm long for all stress
grades
90  45 or 70  70
Struts 1500 to 2400 mm long for all
stress grades
70  70
AS 1684 Span Tables
Roof Member Load Impacts
The loads from roof members often impact on the design
of members lower down in the structure.
This impact can be determined from the following load
sharing calculations:
 Roof Load Width (RLW).
 Ceiling Load Width (CLW).
 Roof area supported.
AS 1684 Span Tables
Roof Member Load Impacts – Roof Load Width
RLW is the width of roof that contributes roof load to a
supporting member. It is used as an input to Span Tables
for:
 Floor bearers.
0
0
0
0
0
3
5
 Wall studs.
1
0
0
 Lintels.
5
1
 Ridge or intermediate beams.
 Verandah beams.
B
Roof Load Widths are measured on
the rake of the roof.
A
AS 1684 Span Tables
Roof Member Load Impacts – Roof Load Width
AS 1684 Span Tables
Roof Member Load Impacts – With Trusses
x y
x y
b
 a RLW wall B =
RLW wall A =
2
2
W
L
R
x
RL
W
y
a
b
A
The roof loads on trusses
are distributed equally
between walls 'A' and 'B'.
B
AS 1684 Span Tables
Roof Member Load Impacts – Without Ridge Struts
For a pitched roof without ridge struts it is assumed that
some of the load from the un-supported ridge will travel
down the rafter to walls 'A' and 'B'. The RLWs for walls A &
B are increased accordingly.
*
*
W
RL
RL
W
W
RL
1
A
RL
W
y
x
a
RL
W
b
2
3
B
x
y
RLW wall A =  a RLW wall B =
b
2
2
AS 1684 Span Tables
Roof Member Load Impacts – With Ridge Struts
RL
WR
LW
RLW
y
x
a
1
A
C
x
Underpurlin 1 = 2
y
Underpurlin 2 =
3
y
Underpurlin 3 =
3
2
b
3
B
AS 1684 Span Tables
Roof Member Load Impacts – Ceiling Load Width
Ceiling load width (CLW) is the width of ceiling that
contributes ceiling load to a supporting member (usually
measured horizontally).
CLW
x
A
B
AS 1684 Span Tables
Roof Member Load Impacts – Ceiling Load Width
CLW is used as an input to Span Tables for hanging beams
and strutting/hanging beams
Ridgeboard
Hanging
beam
Ceiling joist
Roof strut
Hanging
beam span
'x'
Hanging Beam
Strutting beam
Strutting
beam span
Underpurlin
Strutting/Hanging Beam
AS 1684 Span Tables
Roof Member Load Impacts – Ceiling Load Width
FIGURE 2.12 CEILING LOAD WIDTH (CLW)
x
CLW Hanging beam D =
2
y
CLW Strutting/Hanging beam E =
2
EE
D
D
A
CLW
CLW
CLW
CLW
xx
yy
B
C
AS 1684 Span Tables
Roof Member Load Impacts – Roof Area Supported
Example: The Strutting Beam Span Table requires a ‘Roof
Area Supported (m2)’ input. The strutting beam shown
supports a single strut that supports an underpurlin.
The ‘area required’ is the roof area
A/2
supported by the strut.
A
B/2
B
This is calculated as follows:Underpurlin
Roof Area Supported =
A B

2 2
Sum of half the underpurlin spans
either side of the strut (A/2)
multiplied by the sum of half the
rafter spans either side of the
underpurlin (B/2).
Strut
Strutting Beam
Span
Strutting Beam
AS 1684 Span Tables
Strutting Beam Design Example
Inputs required
Wind Classification
Stress Grade
Roof Area Supported
Strutting Beam Span
Single or Continuous Span
Roof Mass (Sheet or Tile)
= N2
= F8
= 6m2
= 2900 mm
= Single
= Steel Sheet (20 kg/m2)
AS 1684 Span Tables
Strutting Beam Design Example
Roof Area Supported = 6m2
Roof = Sheet
Strutting Beam Span = 2900
mm
2 x 140 x 45 mm F17
members are adequate
AS 1684 Span Tables
Wall Framing
WALL FRAMING
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Return to menu
AS 1684 Span Tables
Wall Framing
Timber or metal bracing
Top plate
Sheet
bracing
Common
stud
Lintel
Nogging
Wall
intersection
Bottom plate
Jack stud
Jamb stud
AS 1684 Span Tables
Wall Studs Design Example
Inputs required
Wind Classification
Stress Grade
Notched 20 mm
Stud Height
Rafter/Truss Spacing
Roof Load Width (RLW)
Stud Spacing
Roof Type
= N2
= MGP10
= Yes
= 2400 mm
= 900 mm
= 5000 mm
= 450 mm
= Steel Sheet (20 kg/m2)
Return to menu
Wall Framing – Wall Stud Size
2006
At least
5000mm
70 x 35mm
MGP10 wall studs
are adequate
Simplify table
Inputs required
•
Wind Classification = N2
•
Stress Grade
•
Notched 20 mm
•
Stud Spacing
•
Roof Type
•
Rafter/Truss Spacing= 900 mm
•
Roof Load Width (RLW)
•
Stud Height
= MGP10
= Yes
= 450 mm
= Steel Sheet (20 kg/m2)
= 5000 mm
= 2400 mm
AS 1684 Span Tables
Top Plate Design Example
Inputs required
Wind Classification
Stress Grade
Rafter/Truss Spacing
Roof Load Width (RLW)
Stud Spacing
Roof Type
= N2
= MGP10
= 900 mm
= 5000 mm
= 450 mm
= Steel Sheet (20 kg/m2)
Return to menu
Wall Framing – Top Plate Size
2006
Simplify table
2 x 35x 70mm
MGP10 top plates are
adequate
At least
5000mm
Inputs required
•
Wind Classification = N2
•
Stress Grade
•
Roof Type
•
Rafter/Truss Spacing= 900 mm
•
Tie-Down Spacing
•
Roof Load Width (RLW)
•
Stud Spacing
= MGP10
= Steel Sheet (20 kg/m2)
= 900 mm
= 5000 mm
= 450 mm
AS 1684 Span Tables
Wall Framing – Wall Lintel Design Example
Inputs required
Wind Classification
Stress Grade
Opening size
Rafter/Truss Spacing
Roof Load Width (RLW)
Roof Type
= N2
= F17
= 2400 mm
= 900 mm
= 2500 mm
= Steel Sheet (20 kg/m2)
Wall Framing – Lintel Size
2006
Simplify table
A 140 x 35mm
F17 Lintel is
adequate
Use 1200mm
Inputs required
•
Wind Classification = N2
•
Stress Grade
•
Roof Type
•
Roof Load Width (RLW)
•
Rafter/Truss Spacing= 900 mm
•
Opening size
= F17
= Steel Sheet (20 kg/m2)
= 2500 mm
Use 3000mm
= 2400 mm
AS 1684 Span Tables
Floor Framing
FLOOR FRAMING
Return to menu
AS 1684 Span Tables
Floor Framing – Floor Members
Floor joists
Floor bearers
Platform Floor Sheets
Perimeter Brickwork
AS 1684 Span Tables
Floor Framing – Floor Bearers
Bearers are commonly made from hardwood or engineered
timber products and are laid over sub-floor supports.
Bearers are sized according to span and spacings – typically
a 1.8m (up to 3.6m) grid
Be
are
rs
pa
ci
n
g
Bearer Spacing
r
are
Be
n
spa
Bearer Span
AS 1684 Span Tables
Floor Framing – Floor Load Width Example
If a = 900 mm
x = 2000 mm
y = 4000 mm
FLW A = 1900 mm
FLW B = 3000 mm
FLW C = 2000 mm
AS 1684 Span Tables
Floor Framing – Bearer and Floor Joist Example
Simple rectangular shaped light-weight home
 Gable Roof =25o pitch
 Steel Sheet = 20 kg/m2
 Wind Speed = N2
Floor joists
 Wall Height = 2400 mm
Bearers
3600
Section
4500
Elevation
AS 1684 Span Tables
Floor Framing – Bearer Design Example
Floor Load Width (FLW) Bearers at 1800 mm centres
FLWA = 1800/2 = 900 mm
Bearer A
Supports
both a Roof
Load
And a floor
load
Floor Joists at 450 mm
crs
1800
3600
Section
AS 1684 Span Tables
Floor Framing – Bearer Design Example
x y
a
2
Roof Load Width (FLW) for Wall A =
a = 496 mm
x = 1986 mm
Total RLW On Wall A = 1986 mm (say 2000 mm) + 496
mm (say 500 mm) = 2500 mm
W
RL
x
RL
W
y
a
b
A
B
AS 1684 Span Tables
Floor Framing – Bearer Design Example
Inputs required
• Wind Classification
• Stress Grade
• Floor Load Width (FLW) at A
• Roof Load Width (RLW)
• Single or Continuous Span
• Roof Mass (Sheet or Tile)
• Bearer Span
= N2
= F17
= 900 mm
= 2500 mm
= Continuous
= Steel Sheet (20 kg/m2)
= 1800 mm
Floor Framing – Bearer Size
2006
Simplify table
Inputs required
•
Wind Classification = N2
•
Stress Grade
•
Floor Load Width (FLW) at A
•
Roof Mass (Sheet or Tile)
•
•
Single or Continuous Span
Roof Load Width (RLW)
Bearer Span
2 x 90 x 35mm F17
members joined
together are adequate
= F17
= 900 mm
= Steel Sheet
(20 kg/m2)
= Continuous
= 2500 mm
= 1800mm
Use 1200mm
table
Use 4500mm
AS 1684 Span Tables
Floor Joist Design Example
Inputs required
Wind Classification
Stress Grade
Roof Load Width (RLW)
(just supporting floor loads)
Single or Continuous Span
Roof Type
Joist Spacing
= N2
= F17
= 0 mm
= Continuous (max 1800)
= Steel Sheet (20 kg/m2)
= 450 mm
Floor Framing – Floor Joist Design Example
2006
Simplify table
90 x 35mm F17 floor
joists at 450mm crs
are adequate
At least
1800mm
Inputs required

Wind Classification = N2

Stress Grade
= F17

Joist Spacing
= 450 mm

Roof Type
= Steel Sheet (20 kg/m2)

Single or Continuous Span
= Continuous (max 1800)

Roof Load Width (RLW)
= 0 mm

Joist span
= 1800mm
Further Information
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