PLYWOOD ASSOCIATION OF AUSTRALIA LTD

ACKNOWLEDGEMENT JAS-ANZ
This literature was developed with funding assistance from
the Forest and Wood Products Reseach and Development
Corporation.

FOREST & WOOD PRODUCTS

RESEARCH & DEVELOMPENT CORPORATION
An accredited body under Reg. No Z1460695AB
STRUCTURAL PLYWOOD WALL BRACING
Wind and earthquakes have historically caused damage to low rise buildings in Australia. These potentially
damaging phenomena result in all buildings requiring bracing, especially those with modern open plan designs with
wide openings. Structural plywood provides a simple but reliable means to brace these building frames. This manual
explains to designers and builders how to brace framing in accordance with the new limit state revision of AS1684
‘Residential Timber-Framed Construction’. The change to limit state design allows a more reliable design than
believed possible with permissible stress design. For permissible stress bracing design the design capacities are
given in the appendix of this manual.

BENEFITS OF USING PAA STRUCTURAL PLYWOOD

Safety and Reliability User Friendly
● Guaranteed by the PAA third party audited JAS-ANZ ● Install using simple hand or gun fastener - can fasten
accredited Product Certification Scheme to fully comply within 7mm of edges
with AS/NZS2269 ‘Plywood-Structural’
● Cross-laminated plywood construction resists site,
● Bonded with durable ‘marine’ A bond impact, and edge damage
● Proven performance based on extensive laboratory
testing
Design Feasibility & Cost
Effectiveness
● Written into AS1684 ‘Residential Timber-Framed
● High strength and stiffness in relatively short panels with
Construction’
simple fixings allowing wider windows and reduced
numbers of walls

● Can provide safe and reliable bracing during the

vulnerable construction period

INDEX Why Plywood Bracing 3

Design Methodology Design Approach 3

Design Parameters
Design Criteria

Material Specification Plywood 4

Framing
Fasteners

Establish Design Racking Forces Maximum Design Gust Wind Speed 5

Wind Classification
Area of Elevation
Design Racking Force

Structural Plywood Bracing Systems Standard Range - Flat Head Fasteners 10

Internal Lining - Bullet Head Fasteners

Additional Installation Requirements General 14

Distribution and Spacing of Bracing Walls
Fixing of Bottom of Bracing Walls
Uplift Resistance of Bracing Walls
Fixing of Top of Bracing Walls

Holes Through Plywood Bracing 18

Design Example 18

Appendix 19
Permissible Stress Design Capacities

2
WHY PLYWOOD BRACING
The Australian Standard ‘Residential Timber-Framed The structural plywood bracing systems described in this
Construction’ states “Permanent bracing shall be provided to manual provide a safe and reliable means of permanent
enable the roof, wall and floor framework to resist horizontal bracing that is easy to install and very cost effective.
forces (racking forces) applied to the building. Appropriate
connection shall also be provided to transfer these forces Diagram 1 provides an illustration of how wind forces act on
through the framework and sub-floor structure to the a building.
building’s foundation.”

DIAGRAM 1 : Wind Forces Acting on a Building

The horizontal wind (racking) forces resulting from the wind flow If one applies this logic to double storey construction it can be
on the top half of the external cladding are transferred into the demonstrated the wind forces applied to lower storeys can
ceiling (roof or top floor) diaphragm. These forces can be safely approach 3 times those on the top storey. This fact, coupled with
and reliably resisted by vertical structural plywood shear walls. the trend of having large rooms (with less walls) with wider
The racking forces from the lower half of the external cladding openings and the use of non-structural linings makes the
and those from the plywood bracing are both transferred by the structural design of these modern buildings more critical.
floor (diaphragm) and its supports down into the foundations.

DESIGN METHODOLOGY
Design Approach
1. Establish the wind forces on the walls of the building, 2. Select the appropriate structural plywood bracing system or
perpendicular to the wind flow in the two primary building combination of systems.
dimensions, viz. normal to the building length and width. These 3. Through multiplying the selected bracing resistances by the
forces can be assessed using AS1170.2 ‘Wind Loading Code’, length of each bracing system parallel to the wind direction,
AS4055 ‘Wind Loads for Housing’ or AS1684 ‘Residential ensure the total bracing resistance in these walls equals or
Timber-Framed Construction’. For convenience, Table 4 exceeds the design wind forces in this direction. Do likewise for
provides the wind pressure tables for Wind Classification N2 the other primary direction.
from AS1684.

Design Parameters
1. Buildings whose plan shape is essentially rectangular or a 4. Up to 2.7m wall height. Over 2.7m linearly reduce
combination of rectangular elements. the bracing resistance in the ratio of 2.7m divided by the
2. Maximum building width of 15m. actual height.
3. Maximum roof pitch is 350.

Design Criteria
The following design criteria were applied to the full scale loads were taken prior to the onset of any buckling.
prototype tests done in approved Australian laboratories to the The strength limit state (irrespective of its cause) was
requirements of AS1720.1-1997 ‘Timber Structures Code’ to determined by working backwards from the test panel ultimate
establish limit states for structural plywood sheathed panels. load to establish an Equivalent Test Load (ETL). From this the
1. The allowable deflection i.e., racking out of square, was limited design action effect for the bracing walls were determined.
to panel height/300 or 8mm at the serviceability limit state. 3. The serviceability limit state loads incorporate a minimum
2. Where plywood buckling generated an alternative factor of safety of 2.0 on the ultimate failure load of the prototype
serviceability limit state the design load was taken within the test panels.
Limit of Proportionality of the load/deflection plot i.e., design

3
MATERIALS SPECIFICATION
Permanent structural bracing enables wall systems to resist system and subfloor to the ground. Thus for safety and
horizontal forces i.e. racking forces, applied to the building by reliability of structural bracing the following material
wind and/or earthquake. Appropriate connections are specifications are critical.
required to transfer these forces through a structurally sound

Plywood
To comply with the requirements of this manual the plywood
must be branded with the PAA/JAS-ANZ ‘tested structural’
Product Certification stamp. This stamp ensures the plywood
has been manufactured to the requirements of AS/NZS2269
‘Plywood-Structural’ under the PAA/JAS-ANZ accredited
third party audited, process based, quality assurance
program, and that the plywood will be predictable and reliable
making it fit for purpose in this engineered application.
Framing
The framing must be designed to carry the horizontal forces to timber of a minimum joint strength of J4 or JD4. Additional
and from the plywood. In the case of timber the framing must be testing has verified if the framing is of the lower joint strength
in accordance with the requirements of AS1684, or framing JD5 then the design racking resistances must be reduced by
manual produced in accordance with the design parameters of 121/2%, requiring a proportional increase in the required bracing
AS1684. The testing of bracing on structural timber was on wall length.

Fasteners
Connection of the structural plywood to the framing is critical driven fasteners for timber framing. The spacings for staples
in bracing. In general, the failure in testing was in the are two thirds (i.e. fastener spacing multiplied by 0.66) those
connections. Table 1 specifies the minimum hand or power shown for nails or screws.

TABLE 1: Minimum Fastener Specification

Hand Driven Nails Power Driven Nails Power Driven Staples

2.80mm dia. x 30mm flathead Senco TN22-38 APB (2.33mm Senco N17 BAB
structural clouts or connector dia. x 38mm flathead)
nails
Bostitch CR3D (3.06dia. x 32 Bostitch BCS4-1232
flathead)
Bostitch C45D-250 or AC45P-
250-GW (2.5dia. x 45 flathead)
Jambro B20998 (RBC 2.80mm Jambro A10617
dia. x 32mm zinc plate barb) (G5562-38mm)
Duo-Fast C27/32GD

Notes: 1. Fasteners with equivalent dimension i.e. head size and shape, shank
diameter and length to those in Table 1 are deemed acceptable.
2. All fasteners are to be galvanised or suitably coated.
3. Minimum edge clearance for fasteners is 7mm.
4. If smaller diameter hand driven nails are used, the spacings of nails can
be reduced in the ratio of the basic lateral loads per nail for J4 or JD4 joint
group given in Table 4.1 of AS1720.1 ‘Timber Structures Code’ for the lower
nail diameter relative to the tabulated load for a 2.8mm diameter nail.
5. Fasteners are not to be overdriven.
6. Fasteners for structural plywood linings as detailed in Tables 13 and 14
can be a minimum of 2.5mm dia. x 40mm bullet head nails.
When coach screws or bolts are used to fix plywood panels, Circular washers of equivalent thickness and nett bearing
bottom plates or as tie rods, steel washers must be used. area are an acceptable alternative.
Table 2 provides detail of the minimum allowable washer size.

TABLE 2 : Minimum Steel Washers (mm)

M10 Bolt/Coach Screw 38 x 38 x 2.0
M12 Bolt/Coach Screw 50 x 50 x 3.0
M16 Bolt/Coach Screw 65 x 65 x 5.0

4
ESTABLISH DESIGN RACKING FORCES
The limit state design racking forces can be calculated using prerequisite for use of this simpler method described below is the
AS1170.2 ‘Wind Loading Code’, or more simply, by using the ‘design gust wind speed’ and/or ‘wind classification’, and the ‘area
AS1684 ‘Residential Timber-Framed Construction’ method. The of elevation’.

Maximum Design Gust Wind Speed

The wind speed can be established by a number of methods, viz: (iii) The wind classification can be established by use of AS4055
(i) The Local government Authority may have maps prepared ‘Wind Loads for Housing’ (a rationalised interpretation of
showing wind speed or wind classification zones. AS1170.2).
(ii) The maximum design gust speed can be derived using
AS1170.2.

Wind Classification
The AS1684 wind classification system is a rationalised means of design gust wind speed. Also included in the table is a multiplier to
categorising the wind speeds into bands for the non-cyclonic be applied to the pressures given in Table 4 for other than N2 wind
Regions A and B, and the cyclonic Regions C and D. Table 3 classification.
shows the various wind classifications in terms of the maximum

TABLE 3: Wind Classification in Terms of Wind Speed

Wind Classification Maximum Design Gust Wind Speed (m/s)
Multiplier for wind
Ultimate pressures in
Regions Regions Permissible stress Serviceability limit Table 4
limit state
A and B C and D design state

N1 - 28 26 34 0.72

N2 - 33 26 40 1.00

N3 C1 41 32 50 1.56

N4 C2 50 39 61 2.33

- C3 60 47 74 3.42

Note: The regions are given in detail in AS1170.2 and AS4055. Regions B, C and D occur within 100km of the Australian coast
north of the 300 latitude line (i.e. just north of Coffs Harbour). The balance of Australia being designated as Region A.

Preservative treated structual plywood serving the dual purposes of cladding and of bracing

5
Area of Elevation
The area of elevation, to which the pressures from Table 4 are The wind direction used shall be that resulting in the greatest load.
applied to calculate the design racking force, is proportional to the As wind can blow from any direction, e.g. a single storey dwelling
wind force applied to the frame of the relevant storey of the building. having a gable at one end and hip the other, will result in a higher
The area referred to is the area of the full building elevation above load at right angles to the width of the house when the gable end is
half way up the wall frame for the particular storey of the building facing the wind. For complex building shapes a combination of
being assessed. This is illustrated in Diagram 2. shapes may be considered individually and individual loads added
together later.

(i) Plan

(ii) Wind direction 1

(iii) Wind direction 2

Notes: 1 h = half the height of the wall (half of the floor to ceiling height).
2 For lower storey of two storey section h = half of the height of the lower storey (i.e. lower storey floor to lower storey ceiling).
3 The area of elevation of eaves up to 1000mm wide may be ignored in the determination of area of elevation.

DIAGRAM 2: Determination of Area of Elevation

6
Design Racking Force
The design racking force for each storey or level of the building for The Lateral Wind Pressures for Wind Classification N2 are given
each wind direction is the product of the Area of Elevation and the in Table 4. For other Wind Classifications, the pressures from
relevant wind pressure for the particular Wind Classification, i.e. Table 4 are to be factored down or up using the multiplier given
in Table 3 e.g. for N1 wind classification the pressures from Table
Total Racking Force (kN) = Projected Area of Elevation (m2) 4 are to be multiplied by 0.72.
x Lateral Wind Pressure (kPa).

TABLE 4 : Wind Pressures (kPa) on Projected Area for Wind Classification N2

(a) Single storey, upper of two storey, lower storey or sub-floor - all vertical surface
elevations (gable ends, skillion ends and flat wall surfaces)

Pressure = 0.92kPa

7
Table 4 (cont.)
(b) Single storey or upper of two storey - long length of building - hip or gable ends

Width (m) Roof Pitch (degrees)

0 5 10 15 20 25 30 35
4.0 0.84 0.74 0.67 0.61 0.61 0.72 0.77 0.76
5.0 0.84 0.71 0.64 0.57 0.58 0.69 0.75 0.74
6.0 0.84 0.69 0.61 0.55 0.59 0.70 0.74 0.74
7.0 0.84 0.67 0.58 0.53 0.59 0.70 0.73 0.74
8.0 0.84 0.65 0.56 0.51 0.60 0.71 0.72 0.75
9.0 0.84 0.64 0.54 0.49 0.61 0.71 0.71 0.75
10.0 0.84 0.62 0.52 0.48 0.61 0.72 0.70 0.75
11.0 0.84 0.60 0.50 0.48 0.62 0.72 0.71 0.75
12.0 0.84 0.59 0.47 0.49 0.63 0.72 0.71 0.76
13.0 0.84 0.57 0.45 0.49 0.63 0.73 0.71 0.77
14.0 0.84 0.56 0.43 0.50 0.64 0.73 0.72 0.77
15.0 0.84 0.55 0.42 0.50 0.65 0.73 0.72 0.77
16.0 0.84 0.53 0.40 0.51 0.65 0.73 0.72 0.78

NOTE: 00 degree pitch is provided for interpolation purposes only.

(c) Lower storey or sub-floor - long length of building - hip or gable ends

Width (m) Roof Pitch (degrees)

0 5 10 15 20 25 30 35
4.0 0.84 0.81 0.78 0.75 0.75 0.83 0.85 0.84
5.0 0.84 0.80 0.77 0.73 0.73 0.82 0.84 0.83
6.0 0.84 0.79 0.75 0.72 0.73 0.81 0.83 0.82
7.0 0.84 0.78 0.74 0.70 0.72 0.81 0.82 0.82
8.0 0.84 0.78 0.73 0.69 0.72 0.81 0.81 0.82
9.0 0.84 0.77 0.71 0.68 0.72 0.81 0.80 0.81
10.0 0.84 0.76 0.70 0.67 0.72 0.81 0.79 0.81
11.0 0.84 0.75 0.69 0.66 0.72 0.80 0.79 0.81
12.0 0.84 0.74 0.68 0.66 0.72 0.80 0.79 0.81
13.0 0.84 0.74 0.66 0.66 0.72 0.80 0.79 0.82
14.0 0.84 0.73 0.65 0.66 0.73 0.80 0.79 0.82
15.0 0.84 0.72 0.64 0.66 0.73 0.80 0.79 0.82
16.0 0.84 0.72 0.63 0.66 0.73 0.80 0.79 0.82

NOTE: 00 degree pitch is provided for interpolation purposes only.

8
Table 4 (cont.)
(d) Single storey or upper of two storey - short end of building - hip ends

Width (m) Roof Pitch (degrees)

0 5 10 15 20 25 30 35
4.0 0.92 0.86 0.81 0.77 0.76 0.79 0.82 0.81
5.0 0.92 0.84 0.79 0.74 0.73 0.77 0.81 0.79
6.0 0.92 0.83 0.77 0.72 0.73 0.77 0.79 0.79
7.0 0.92 0.82 0.75 0.70 0.73 0.77 0.78 0.79
8.0 0.92 0.80 0.73 0.68 0.72 0.77 0.77 0.79
9.0 0.92 0.79 0.71 0.66 0.72 0.77 0.76 0.79
10.0 0.92 0.78 0.69 0.65 0.72 0.77 0.75 0.78
11.0 0.92 0.77 0.68 0.64 0.72 0.77 0.75 0.79
12.0 0.92 0.76 0.66 0.64 0.72 0.77 0.75 0.79
13.0 0.92 0.75 0.64 0.64 0.73 0.77 0.75 0.79
14.0 0.92 0.73 0.62 0.64 0.73 0.77 0.76 0.79
15.0 0.92 0.72 0.60 0.64 0.73 0.77 0.76 0.80
16.0 0.92 0.71 0.59 0.64 0.73 0.77 0.76 0.80

NOTE: 00 degree pitch is provided for interpolation purposes only.

(e) Lower storey or sub-floor - short end of building - hip ends

Width (m) Roof Pitch (degrees)

0 5 10 15 20 25 30 35
4.0 0.92 0.90 0.89 0.87 0.86 0.87 0.88 0.87
5.0 0.92 0.90 0.88 0.85 0.85 0.86 0.87 0.87
6.0 0.92 0.89 0.87 0.84 0.85 0.86 0.87 0.86
7.0 0.92 0.89 0.86 0.84 0.84 0.86 0.86 0.86
8.0 0.92 0.88 0.85 0.83 0.84 0.85 0.85 0.86
9.0 0.92 0.88 0.84 0.82 0.84 0.85 0.84 0.85
10.0 0.92 0.87 0.84 0.81 0.83 0.85 0.84 0.85
11.0 0.92 0.87 0.83 0.80 0.83 0.85 0.84 0.85
12.0 0.92 0.86 0.82 0.80 0.83 0.85 0.83 0.85
13.0 0.92 0.86 0.81 0.80 0.83 0.84 0.83 0.85
14.0 0.92 0.85 0.80 0.80 0.83 0.84 0.83 0.85
15.0 0.92 0.85 0.79 0.79 0.83 0.84 0.83 0.85
16.0 0.92 0.85 0.78 0.79 0.83 0.84 0.83 0.85

NOTE: 00 degree pitch is provided for interpolation purposes only.

9
 STRUCTURAL PLYWOOD BRACING SYSTEMS
After establishing the design racking forces for each storey or bottom and top plates must be a minimum of 70 x 70mm F5
level and in both primary directions, a building frame can be or 90 x 45mm F5 or equivalent.
braced by installing sufficient length of an appropriate
system or a combination of the structural plywood bracing The bracing resistances given in Tables 5-14 are applicable
systems shown in Tables 5 to 14. to frames sheathed one side only. The resistances are
additive for frames sheathed on two sides, however, the hold
It is good practice to use bracing in all corners in external down requirements of the bottom plate must also be
walls for each direction and level. Additionally, it is necessary increased accordingly. Bottom plate sizes should be checked
to use an even distribution of bracing rather than to under these circumstances to ensure safe moment capacity.
concentrate a large proportion of the bracing resistance in a
comparatively short length of a high capacity bracing If approved staples are used the spacings are to be a
resistance system. The distribution and maximum spacings maximum of two thirds those for nails or screws shown in
are detailed in the section Additional Installation Tables 5 to 14.
Requirements.
The allowable design resistances are appropriate to all
The bracing resistances shown in Tables 5-14 apply to wall species, joint strength groups to J4 or JD4 and stress grades
frames up to a height of 2.7m. For wall heights over 2.7m the of wall framing timber. This covers most Australian hardwood
bracing is reduced in the ratio of 2.7m divided by the higher and exotic pines. If species of JD5 joint strengths are used
wall height, e.g. with a 3m high frame, this reduction factor then additional testing has shown that the design values
would be 0.9 . should be reduced 12.5%. Imported unidentified softwood
For bracing system resistances greater than 6.4kN/m the may fall into this category.

TABLE 5: Minimum Structural Plywood Thicknesses for 3kN/m Bracing Capacity Systems (mm)
Plywood Stud Horizontal Butt Joints Permitted
Provided fixed to Nogging at
Stress Spacing 100mm Centres
100mm
Grade 600mm
100mm
(max)
F8 7
F11 4.5 100mm
Fastener Centres:
F14 4 100mm Top and Bottom Plate
100mm Vertical Edges
F27 3 100mm Intermediate Studs

100mm
NOTE: These systems are only applicable to
sheathed sections a minimum of 900mm wide.

TABLE 6: Minimum Structural Plywood Thicknesses for 3.4kN/m Bracing Capacity Systems (mm)
Plywood 150mm
Stress Stud Spacing Horizontal Butt Joints
Grade Permitted Provided fixed to
Nogging at150mm Centres
450mm 600mm
F8 7 9 150mm

F11 4.5 7 150mm

F14 4 6
F27 3 4.5
Fastener Centres:
150mm Top and Bottom Plate
150mm Vertical Edges
300mm Intermediate Studs

NOTE: For sheathed systems less than 900mm in

width the appropriate reduction factor from Table 9
300mm
must be applied to the 3.4kN/m bracing capacity.

10
TABLE 7: Minimum Structural Plywood Thicknesses for Alternate 3.4kN/m Systems Utilising Nogging (mm)
Plywood Stud Spacing
Stress 600mm 150mm Horizontal Butt Joints Permitted
Grade (max) Provided fixed to Nogging at
150mm Centres
F8 7
F11 4.5
F14 4 150mm 1 row of Nogging
F27 3 Staggered or Single Line
at Half Wall Height

150mm

Fastener Centres:
150mm Top and Bottom Plate
NOTE: For sheathed systems less than 900mm in 150mm Vertical Edges
150mm Nogging
width the appropriate reduction factor from Table 9 300mm Intermediate Studs
must be applied to the 3.4kN/m bracing capacity.

300mm

TABLE 8: Minimum Structural Plywood Thicknesses for 6.4kN/m Bracing Capacity Systems (mm)
Plywood
Stud Spacing M12 Rod Top to Bottom plate
Stress Each End of Sheathed Section*
150mm
Grade 450mm 600mm
F8 7 9 Horizontal Butt Joints Permitted
Provided fixed to Nogging at
F11 6 7 150mm Centres
F14 4 6
F27 4 4.5 150mm
Fastener Centres:
150mm Top and Bottom Plate
150mm Vertical Edges
300mm Intermediate Studs

NOTE: For sheathed systems less than 900mm in Sheathed Panels are to be
Connected to Sub-Floor by
width reduction factors from Table 9 must be applied. a minimum of 13kN tie
For 600mm or wider sections the fitting of M10 down every 1200mm
between rods. *An exception
Coachscrews are not required to achieve the reduction to the requirement for tie rods
300mm for each end is when 6.4N/m
factor of 1 as the two M12 tie rods make them systems are used either side
of an opening up to 2.4m - in
superfluous. such a case tie rods at the
opening are not mandatory.

TABLE 9: Racking Resistance Reduction Factors

Width of Sheathed Reduction Width of short
Section (m) Factor bracing panel

0.6 0.5
0.45 0.25
0.3 0.2
0.6 (with M10 coach 1.0
screws at the panel
corners)

Plywood Corner Detail

Bracing To obtain reduction
factor of 1 for 0.6m
NOTES: sheathed sections
1. Reduction factors can be interpolated as given in Table 9
position one M10
2. Reduction factors can only be applied to systems detailed coach screw with
washer in each
in Tables 6, 7 and 8. corner of braced
3. A 600mm or wider section of the 6.4kN/m system detailed section through
plywood into plate.
in Table 8 with the M12 rods fitted does not require the Not required for
other reduction
fitting of the M10 coach screws to achieve the reduction factors.
factor of 1.0.

11
 TABLE 10: Minimum Structural Plywood Thicknesses 6kN/m Bracing Capacity Systems (mm)
Plywood
Stud Spacing Horizontal Butt Joints
Stress 50mm Staggered Permitted Provided fixed to
Nogging at 50mm Centres
Grade 450mm 600mm
F8 7 9 50mm

F11 6 7 150mm
F14 4 6
F27 4 4.5
Fastener Centres:
50mm Top and Bottom Plate
150mm Vertical Edges
300mm Intermediate Studs

Sheathed Panels are to be

Connected to Sub-Floor by
a minimum of 13kN tie
300mm down at each end and
NOTE: These systems are only applicable to every 1200mm

sheathed sections a minimum of 900mm width

TABLE 11: Minimum Structural Plywood Thicknesses for 7.5kN/m Bracing Capacity Systems (mm)
Plywood
Stud Spacing M12 Rod Top to Bottom plate
Stress Each End of Sheathed Section
Grade 50mm
450mm 600mm
F11 4.5 4.5 Horizontal Butt Joints Permitted
Provided fixed to Nogging at
50mm Centres

100mm
Fastener Centres:
50mm Top and Bottom Plate
100mm Vertical Edges
100mm Intermediate Studs

Sheathed Panels are to be

Connected to Sub-Floor by
a minimum of 13kN tie
100mm down every 600mm
between rods.
Bottom and Top plates must be
NOTE: These systems are only applicable to a minimum of 70 x 70mm F5 or
90 x 45 F5 or equivalent
sheathed sections of a minimum of 900mm width

TABLE 12: Minimum Structural Plywood Thicknesses for 8.7kN/m Bracing Capacity Systems (mm)
Plywood
Stud Spacing M12 Rod Top to Bottom plate
Stress Each End of Sheathed Section
Grade 50mm
450mm 600mm
F11 7.0 7.0 Horizontal Butt Joints Permitted
Provided fixed to Nogging at
50mm Centres

100mm
Fastener Centres:
50mm Top and Bottom Plate
100mm Vertical Edges
100mm Intermediate Studs

Sheathed Panels are to be

Connected to Sub-Floor by
a minimum of 13kN tie
100mm down every 600mm
between rods.
Bottom and Top plates must be
a minimum of 70 x 70mm F5 or
NOTE: These systems are only applicable to 90 x 45 F5 or equivalent
sheathed sections a minimum 900mm width

12
Internal Lining - Bullet Head Fasteners

Decorative structural plywood wall lining fixed with be punched just below the plywood surface and the
2.5mm dia x 40mm bullet head nails can provide holes filled with a suitable putty. In grooved plywood
bracing resistance against wind loads. The nails may lining the nails may be in the grooves.

Table 13: Minimum Structural Plywood Lining Thicknesses for 2.1kN/m Bracing Resistance (mm)
Plywood
Stud Spacing
Stress Horizontal Butt Joints Permitted
Provided fixed to Nogging at
Grade 450mm 600mm 100mm Centres
100mm
F11 6 6
100mm

100mm
Fastener Centres:
100mm Top and Bottom Plate
100mm Vertical Edges
200mm Intermediate Studs

200mm

NOTE: This system is only applicable to sheathed

sections a minimum of 900mm width

TABLE 14: Minimum Structural Plywood Glue/Nailed Lining for 5.3kN/m Bracing Resistance
Plywood
Stud Spacing
Stress 200mm
Grade 450mm 600mm Horizontal Butt Joints
F11 6 6 Permitted Provided fixed
to Nogging at 200mm
Centres
200mm
200mm

NOTES: 1. A continuous 6mm bead of a elastomeric Fastener Centres:

200mm Top and Bottom Plate
adhesive to be applied to all nailed 200mm Vertical Edges
plywood joints to framing timbers, a 200mm Intermediate Studs

double glue bead to be used where

Sheathed Panels are to be
plywood sheets butt together on a stud Connected to Sub-Floor
by a minimum of 13kN
or nogging. tie down at each end
200mm
2. This system is only applicable to and every 1200mm

sheathed sections a minimum of 900mm.

13
 ADDITIONAL INSTALLATION REQUIREMENTS
General
To ensure the maximum effectiveness of structural All fasteners shall be a minimum of 7mm from the plywood
plywood bracing the additional installation requirements edges. All plywood panel butt joints, either at vertical or
detailed in this section are critical. The even distribution horizontal edges, must be via connection of each panel to
and maximum spacing of the bracing panels is vitally a common nogging or stud. Unattached panel edges or ‘fly
important to the structural performance of the structure. joints’ are not permitted.
The tie down of the bottom plate against sideways forces,
and the panels against overturning forces within the Each plywood bracing panel must be effectively fastened
building framework, are crucial to the performance of the to the top and bottom plates and studs. In cases where
bracing. In addition, there must be sufficient structural secondary (ribbon) top plates are employed and the
connection between the ceiling/roof diaphragms and the plywood bracing has been fixed to the lower top plate, the
top of the bracing walls to transfer the forces through the two plates must be connected together with fasteners of
structure to the shear wall then down to the ground. equivalent lateral shear capacity to the plywood to lower
top plate fixings.

Distribution and Spacing of Bracing Walls

The bracing should be approximately evenly distributed angles to the wind direction. Too large a distance will result
throughout the building and provided in both primary in excessive forces being transferred to non-structural
directions. Where possible, bracing should be placed at elements of the building. For wind classifications up to and
the external corners of the building, with the balance including N2 this distance must not exceed 9000mm. For
evenly distributed in the external and internal walls. The higher wind classifications the maximum spacing is to be
object is to distribute the bracing in proportion to the areas in accordance with Table 15 for the relevant wind
of elevation, which, as these areas are proportional to the classification, ceiling depth and roof pitch. Where bracing
design racking forces, will result in the most effective cannot be placed in external walls because of openings
structural solution for the building. and the like, a specifically designed structural plywood
diaphragm floor, ceiling or roof can be used to transfer
The other important criteria for distribution of the bracing racking forces through to bracing walls that are designed
is the maximum distance between bracing panels at right to carry the loads.

DIAGRAM 3: Illustrates Distribution and Spacing of Bracing Walls

Notes: 1. Internal wall bracing can be cupboard backs or in rooms with shorter walls.
2. Where possible some bracing should be placed at all external corners of the building.

14
 Distribution and Spacing of Bracing Walls (cont.)

TABLE 15: Maximum Spacing of Bracing Walls for-

(a) N1 and N2 Wind Classification-Maximum Bracing Wall Spacing - 9m

(b) N3 and C1 Wind classification

Ceiling
Depth Maximum Bracing Wall Spacing (m)
(m)
Roof Pitch (Degrees)
0 5 10 15 17.5 20 25 30 35
<4 5.9 6.6 7.4 7.5 7 6.4 5.1 4.4 4.2
5 7.4 8.3 9 9 8.6 7.9 6 5 4.7
6 8.9 9 9 9 9 8.8 6.7 5.6 5.1
7 9 9 9 9 9 9 7.1 6.1 5.5
8 9 9 9 9 9 9 7.6 6.7 5.7
9 9 9 9 9 9 9 7.9 7.2 5.9
10 9 9 9 9 9 9 8.4 7.9 6.2
11 9 9 9 9 9 9 8.7 7.9 6.4
12 9 9 9 9 9 9 9 7.9 6.6
13 9 9 9 9 9 9 9 8.1 6.6
14 9 9 9 9 9 9 9 8.3 6.7
15 9 9 9 9 9 9 9 8.4 6.8
16 9 9 9 9 9 9 9 8.6 6.9

(c) N4 and C2 Wind Classification

Ceiling
Depth Maximum Bracing Wall Spacing (m)
(m)
Roof Pitch (Degrees)
0 5 10 15 17.5 20 25 30 35
<4 3.9 4.3 4.9 5 4.6 4.2 3.4 2.9 2.8
5 4.9 5.4 6.1 6.2 5.7 5.2 4 3.3 3.1
6 5.9 6.6 7.3 7.4 6.5 5.8 4.4 3.7 3.4
7 6.9 7.9 8.6 8.3 7.2 6.3 4.7 4 3.7
8 7.9 9 9 9 7.7 6.7 5 4.4 3.8
9 8.8 9 9 9 8.4 7.1 5.2 4.8 3.9
10 9 9 9 9 8.9 7.4 5.5 5.2 4.1
11 9 9 9 9 9 7.7 5.8 5.2 4.1
12 9 9 9 9 9 7.9 5.9 5.2 4.3
13 9 9 9 9 9 8.1 6.1 5.3 4.3
14 9 9 9 9 9 8.2 6.1 5.5 4.4
15 9 9 9 9 9 8.5 6.3 5.5 4.5
16 9 9 9 9 9 8.6 6.5 5.7 4.6

(d) C3 Wind Classification

Ceiling
Depth Maximum Bracing Wall Spacing (m)
(m)
Roof Pitch (Degrees)
0 5 10 15 17.5 20 25 30 35
<4 2.7 3 3.4 3.5 3.2 3 2.3 2 1.9
5 3.4 3.8 4.3 4.4 4 3.6 2.8 2.3 2.2
6 4.1 4.6 5.1 5.1 4.6 4.1 3.1 2.6 2.4
7 4.8 5.5 6 5.8 5 4.4 3.3 2.8 2.6
8 5.5 6.3 6.7 6.5 5.4 4.7 3.5 3.1 2.6
9 6.2 7.1 7.6 7.2 5.9 5 3.7 3.3 2.7
10 6.8 7.9 8.3 7.8 6.2 5.1 3.9 3.6 2.9
11 7.5 8.7 9 8.4 6.5 5.3 4 3.6 2.9 NOTES: 1. For wind classifications refer to Table 2.
12 8.2 9 9 8.6 6.7 5.5 4.1 3.7 3 2. Where a structural plywood diaphragm
13 8.9 9 9 8.9 6.9 5.7 4.3 3.7 3 ceiling is used the maximum spacings may
14 9 9 9 9 7.1 5.7 4.3 3.8 3.1 be increased by multiplying the spacing in
15 9 9 9 9 7.2 5.9 4.4 3.9 3.1 the Table by 1.5 provided the bracing wall
16 9 9 9 9 7.4 6 4.6 4 3.2 spacing does not exceed 9m.

15
 Fixing of Bottom of Bracing Walls
The horizontal forces due to wind and earthquakes being The second action is due to rotation or overturning and is
resisted by bracing walls results in two separate types of best resisted by tie rods from the top plate to the sub-floor
action on the bracing panels. The first action is a sideways and located at each end of the bracing wall. For the lower
sliding force pushing on the bottom plate. Sufficient fixings capacity bracing walls connection of the bottom plate to
of the bottom plate to the sub-floor can be designed to the sub-floor can overcome these overturning moments.
resist this sideways ‘shear’ force.

Bottom Plate Fixing for up to 3.4kN/m Systems

No additional bottom plate fixing is required for these both sides of a frame to double the bracing capacity in
lower capacity bracing systems. Obviously, nominal that section of wall, then the bottom plate fixing will
bottom plate fixing as specified in AS1684 is still need to be upgraded to be equivalent for a 6.4kN/m
required. However, if the 3.4kN/m system is used on system. Table 16 details nominal bottom plate fixings.

TABLE 16: Nominal Bottom Plate Fixing for up to 3.4kN/m Bracing

Wind Concrete Slab Hardwood or Softwood or Low
Classification Sub-Floor Cypress Sub-Floor Density Timber Sub-Floor
N1, N2, N3 and C1 75mm masonary nails, screws or 2 only 3.15mm nails at 600mm maximum spacing 2 only 3.75mm nails at 600mm maximum spacing
bolts at 1200mm maximum spacing 75mm long nails for up to 38mm thick plates or 90mm 75mm long nails for up to 38mm thick plates or
long nails for plates 38 to 50mm thick. 90mm long nails for plates 38 to 50mm thick.

C2 75mm masonary nails, screws or Not applicable Not applicable

bolts at 900mm maximum spacing

C3 75mm masonary nails, screws or Not applicable Not applicable

bolts at 600mm maximum spacing

Bottom Plate Fixing for 5.3, 6.0 and 6.4kN/m Systems

The minimum fixing requirement for 5.3, 6.0 and width galvanised looped strap as shown in Diagram 4 is
6.4kN/m bracing capacity systems is 13kN tie down equivalent to 13kN tie down.
every 1200mm or equivalent. A looped 30mm x 0.8mm

DIAGRAM 4: Looped Strap Bottom Plate Fixing

The tie down capacity of some bolts through a range of appropriately embedded. For lower capacity bolt joints
timber joint strengths are presented in Table 17. If the the resistance can be accomplished by reducing the
bolts are used in concrete slabs they must be spacing of the bolts.

TABLE 17: Tie Down Capacity of Bolts through Timber (kN)

Bolt J2 J3 J4 JD4 JD5 JD6
Classification
M10 18 18 18 15 12 9
M12 27 27 26 20 16 12
M16 50 50 46 35 28 21

16
Bottom Plate Fixing for 7.5 and 8.7kN/m Systems
The minimum fixing requirement as used in the actual tie down every 600mm or equivalent. Reference to the tie
testing of 7.5 and 8.7kN/m bracing capacity systems is 13kN down capacities shown in Table 17 provides some guidance.

Uplift Resistance of Structural Plywood Sheathed Walls

Plywood sheathed wall frames can provide roof hold-down at least 13kN tie down every 1200mm or equivalent to
by transferring the wind uplift loads through the rafter or meet the required uplift. Connection of the plates to the
trusses to the top plate, then from the top plate to the plywood is critical. When installed as specified in Table 18,
bottom plate through the plywood acting in tension. The the plywood sheathed wall sections act as a continuous
loads are then transferred to the sub-floor or floor by the cyclone rod thereby avoiding stress concentrations. The
appropriate connection of the bottom plate to floor joists or uplift resistances given in Table 18 were based on
concrete slab. The bottom plate to sub-floor fixing must be prototype testing full panels.

DIAGRAM 5: Uplift Resistance of

Plywood Sheathed
Wall Frames

Table 18 gives the allowable uplift resistance in kN per rafter stress grades given in Tables 5 to 12. A single 900mm
for two plywood to top and bottom plate connection methods. bracing panel can provide the specified uplift resistance for a
The fastener specification is as detailed in Table 1 and the rafter if the rafter is fixed a minimum of 300mm from either
uplift resistances apply to all the plywood thicknesses and end of the plywood panel as shown in Diagram 5.

TABLE 18: Allowable Uplift Resistance of

Plywood Sheathed Wall Systems

Allowable Fastener Spacing (mm)

Uplift Resistance
(kN/Rafter) Hand or Power
Staples
Driven Nails
16.7 50 33
10.4 150 100

The design of the rafter or truss to top plate connection is

critical. The connection design can be as per AS1684.
Alternatively, the connection shown in Diagram 6 is DIAGRAM 6 : Connection of Top Plate to Rafter
acceptable for both uplift resistances given in Table 18. or Truss

17
 Fixing of top of bracing walls
If the horizontal forces due to wind or earthquakes in transferred into the wall bracing there must be sufficient
the ceiling/top floor/roof diaphragm are to be structural connection between the two.

Internal Bracing Walls

All internal bracing walls have to be fixed to the ceiling the bracing capacity of the particular bracing wall.
or roof frame and/or to the external wall frame with AS1684 provides a range of suitable connections.
structural connections of equivalent shear capacity to

External Bracing Walls Under Ends of Eaves

If external walls under ends of eaves are used as and connecting the panel to the top of the bracing wall
bracing walls they have to be structurally connected to and to the ceiling diaphragm with equivalent nailing to
the main ceiling diaphragm. This can be achieved by the wall bracing.
fixing structural plywood bracing to the rafter overhangs

DIAGRAM 7: Plan View External Bracing Under Ends of Eaves

HOLES THROUGH PLYWOOD BRACING

During construction, for various reasons, tradespeople envelope but their centres must be no closer than
often wish to make penetrations through structural 600mm.
plywood bracing panels. A neat hole (i.e. not overcut) of
up to 100mm x 100mm within an envelope of 100mm One hole of up to 400mm x 400mm located between
from the vertical and top edges and 200mm of the studs and within the envelope defined above, with
the bottom edge of the bracing panel will have nogging framing the hole and fixing of the plywood to
no significant effect on the bracing capacity. Multiple the framing as per the requirements for the top and
100mm x 100mm holes are allowable within the bottom plate is acceptable.

DESIGN EXAMPLE
Determine the bracing requirements for a 15m x 9m Assume the Local Authority has advised the Wind
double storey gable roofed dwelling with 200 roof pitch Classification for the site to be N2.
and 2.7m ceiling heights as shown in Diagram 8.

DIAGRAM 8 : Building Dimensions for Design Example

Firstly, the wind forces to be resisted by the building been given, the next step is to calculate the Areas of
frames in both primary directions and for both storeys Elevation using the dimensions from Diagram 8 as
need to be established. As the Wind Classification has detailed in Table 19.

18
DESIGN EXAMPLE (cont.)
TABLE 19: Areas of Elevation for Design Example
Storey Wind Direction Calculation Area of Elevation
(m2)
Upper A 15m x 3.1m 46.5
B 9m x 1.35m + 9m x 1.75m/2 20
Lower A 15m x 5.8m 87
B 9m x 4.05m + 9m x 1.75m/2 44.3

The second step, as detailed in Table 20, is to calculate and storey using the Area of Elevation and the relevant
the Design Racking Forces for each primary direction Wind Pressure from Table 4.

TABLE 20: Design Racking Forces for Design Example

Storey Wind Area of Wind Pressure Calculation Design
Elevation Racking Force
Direction (m2) (kPa) (kN)
Upper A 46.5 0.61 - Table 4 (b) 46.5 x 0.61 28.4
B 20 0.92 - Table 4 (a) 20 x 0.92 18.4
Lower A 87 0.72 - Table 4 (c) 87 x 0.72 62.6
B 44.3 0.92 - Table 4 (a) 44.3 x 0.92 40.8
NOTE: For other Wind Classifications the Design structural bracing spacing requirements. If it is decided
Racking Force can now be reduced or increased using the rodded systems (Tables 10 to 12) will not be
the multiplier given in Table 3. specified then the 6kN/m close nailed system will be
the one with the largest capacity.
The final step is to select the appropriate bracing
systems and calculate the minimum number of For this design example we will nominate 3.4kN/m
structural plywood bracing panels required. In selecting systems on the top floor and 6kN/m on the lower floor.
the bracing systems it is good practice to use lower Additionally, we will assume the stud spacing to be
capacity systems in top storey or single storey frames 450mm, thus 900mm wide structural plywood panels
and higher capacity systems in the lower storey frames. would be the most practical panel width. Table 21
This practice lends itself to having bracing placed in all shows how to calculate the minimum bracing
the building corners and meeting the maximum requirement.

TABLE 21: Calculation of Number of Bracing Panels Required

Storey Wind Calculation Bracing Number of 900mm
Required
Direction (Force/Capacity) (m) Panels Required
Upper A 28.4/3.4 8.4 8.4/0.9 = 9.3 i.e. 10 @ 3.4kN/m
B 18.4/3.4 5.4 5.4/0.9 = 6 i.e. 6 @ 3.4kN/m
Lower A 62.6/6 10.4 10.4/0.9 = 11.6 i.e. 12 @ 6kN/m
B 40.8/6 6.8 6.8/0.9 = 7.6 i.e. 8 @ 6kN/m

Table 21 provides one option for minimum AS1684 for wind direction A will require some of the bracing to
bracing requirements, and all that remains now is to be installed in internal walls, as the relevant external
evenly distribute the panels throughout the framing. To walls are spaced at 15m. These panels can be located
brace the frames in both storeys for wind direction B, in the backs of built-in cupboards, or on the walls of
installation of the plywood in the front and back 15m smaller rooms, e.g. toilets. Decorative structural
walls of both storeys, preferably at each corner, would plywood wall panelling is another alternative. It must be
meet the Code requirements as these walls are 9m remembered these internal bracing walls have to be
apart - the maximum allowed in Table 15 for Wind structurally connected to the ceiling/roof framing to be
Classifications N1 and N2. The bracing of the framing effective as bracing.

APPENDIX Table Ultimate Limit State Permissible Stress

Permissible Stress Design Capacities Number Capacity Design Capacity
For reference, Table 22 lists the appropriate 5 3kN/m 2kN/m
permissible stress capacities for the structural plywood 6 3.4kN/m 2.25kN/m
bracing systems detailed in this brochure. 8 3.4kN/m 2.25kN/m
9 6kN/m 4kN/m
10 6.4kN/m 4kN/m
11 7.5kN/m 5kN/m
12 8.7kN/m 6.5kN/m
TABLE 22: Permissible Stress Bracing 13 2.1kN/m 1.5kN/m
Capacities Design 14 5.3kN/m 3.5kN/m

19
 ADDITIONAL PAA LITERATURE

The following technical manuals and publications are available from Plywood Association of Australia.

• Plywood Webbed Structural Beams for • Plywood Association of Australia Ltd. - Role
Domestic Housing - 50 pages and Activities - 8 pages

• Featuring Plywood in Buildings - 16 pages • Plywood Association of Australia Ltd. -

Quality Control and Product Certification
• T&G Structual Plywood for Residential - 2 pages
Flooring - 8 pages
• Design Guide for Plywood Webbed Beams
• LP91 Low Profile Stressed Skin Plywood - 16 pages
Floor System - 8 pages
• New Joint Australian & New Zealand
• Timber Tops for Concrete Slabs - 8 pages Standard for Structual Plywood - 4 pages

• Structual Plywood for Commercial and • Plywood - the Only Engineered Wood Panel
Industrial Flooring - Design Manual - 12 - 4 pages
pages
• Facts About Plywood - 42 pages
• Plywood in Concrete Formwork - 56 pages
PLYWOOD ASSOCIATION OF AUSTRALIA LTD.,
JAS-ANZ
PLYWOOD ASSOCIATION OF AUSTRALIA LTD.
(A.C.N. 009 704 901)
‘PLYWOOD HOUSE’, 3 DUNLOP STREET, NEWSTEAD, QUEENSLAND, AUSTRALIA
P.O. Box 2108, Fortitude Valley, M.A.C. Qld. 4006. Phone (07) 3854 1228 ● Fax (07) 3252 4769 ISO 9002 NATA CERTIFIED

An accredited body listed under Registration Number S1220792AS

email: folk@plywoodassn.com.au QUALITY SYSTEM CERTIFIED TO AS/NZS/ISO9002

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20