the applicable annual probability of design event for safety, determined by—
assigning the building or structure an Importance Level in accordance with Table B1D3a; and
determining the corresponding annual probability of exceedance in accordance with WA Table B1D3b; and
AS/NZS 1170.2, except where varied by WA Part B2; and
AS/NZS 1170.3 as appropriate; and
AS 1170.4; and
in cyclonic areas, metal roof cladding, its connections and immediate supporting members must comply with Specification 4; and
for the purposes of (v), cyclonic areas are those determined as being located in wind regions B2, C and D in accordance with AS/NZS 1170.2, except where varied by WA Part B2.
Actions not covered in (a), (b) and (c) above:
the nature of the action; and
the nature of the building or structure; and
the Importance Level of the building or structure determined in accordance with Table B1D3a; and
AS/NZS 1170.1.
For the purposes of (d) the actions include but are not limited to—
liquid pressure action; and
ground water action; and
rainwater action (including ponding action); and
earth pressure action; and
differential movement; and
time dependent effects (including creep and shrinkage); and
thermal effects; and
ground movement caused by—
swelling, shrinkage or freezing of the subsoil; and
landslip or subsidence; and
siteworks associated with the building or structure; and
Table B1D3a Importance Levels of buildings and structures
Importance level
Building Types
1
Buildings or structures presenting a low degree of hazard to life and other property in the case of failure.
2
Buildings or structures not included in Importance Level 1, 3 and 4.
3
Buildings or structures that are designed to contain a large number of people.
4
Buildings or structures that are essential to post-disaster recovery or associated with hazardous facilities.
Insert WA table (B1D3b) B1D3 as follows:
WA Table B1D3b: Design events for safety
Importance Level
Annual probability of exceedance for non-cyclonic wind
Annual probability of exceedance for cyclonic wind other than Wind Region D north of the Tropic of Capricorn
Annual probability of exceedance for cyclonic wind in Wind Region D north of the Tropic of Capricorn
Annual probability of exceedance for snow
Annual probability of exceedance for earthquake
1
1:100
1:200
1:250
1:100
1:250
2
1:500
1:500
1:1000
1:150
1:500
3
1:1000
1:1000
1:2000
1:200
1:1000
4
1:2000
1:2000
1:5000
1:250
1:1500
Notes
B1D3(a)(iv) does not take effect until 1 October 2023.
Exemptions
B1D3(a)(iv) does not apply to a Class 7b building—
where 100% of the roof area is shaded for more than 70% of daylight hours; or
with a roof area of not more than 55m2; or
where more than 50% of the roof area is used as a terrace, carpark, roof garden, roof light or the like.
Explanatory information
In Western Australia state variations apply to wind regions B and D, this includes wind region B2 as referenced in AS/NZS 1170.2.
The state variation for wind region B or B2 will ensure that designers consider the combination of peak external pressures and increased internal pressures in design of buildings and use a cyclonic (C) classification instead of non-cyclonic (N) classification. The definition of design wind speed is varied in WA Schedule 1 to identify that wind region B is a C classification in Western Australia. Other changes have also been made to reflect this.
In addition to a variation to clauses B1D3 and B1D4, a variation is made to the application of AS/NZS 1170.2 when used as either a primary referenced document or a secondary or subsequent referenced document. Refer to WA Schedule 2 and WA Part B2.
The state variation for wind region D applies only to those parts of region D located north of the Tropic of Capricorn. The 2021 edition of AS/NZS 1170.2 includes a reduction in design wind speeds for wind region D. The variation will retain similar design wind speeds for wind region D as the 2011 edition of AS/NZS 1170.2 previously referenced in the National Construction Code.
Annual probability of exceedance for non-cyclonic wind
Annual probability of exceedance for cyclonic wind other than Wind Region D north of the Tropic of Capricorn
Annual probability of exceedance for cyclonic wind in Wind Region D north of the Tropic of Capricorn
Annual probability of exceedance for snow
Annual probability of exceedance for earthquake
1
1:100
1:200
1:250
1:100
1:250
2
1:500
1:500
1:1000
1:150
1:500
3
1:1000
1:1000
1:2000
1:200
1:1000
4
1:2000
1:2000
1:5000
1:250
1:1500
WA B1D4 Determination of structural resistance of materials and forms of construction2019: B1.4
Delete clause B1D4 and insert WA B1D4 as follows:
The structural resistance of materials and forms of construction must be determined in accordance with the following, as appropriate:
Masonry (including masonry-veneer, unreinforced masonry and reinforced masonry): AS 3700, except—
‘(for piers—isolated or engaged)’ is removed from Clause 8.5.1(d); and
where Clause 8.5.1 requires design as for unreinforced masonry in accordance with Section 7, the member must also be designed as unreinforced masonry in accordance with Tables 10.3 and 4.1(a)(i)(C) of AS 3700.
Concrete:
Concrete construction (including reinforced and prestressed concrete): AS 3600.
Autoclaved aerated concrete: AS 5146.1.
Post-installed and cast-in fastenings: AS 5216.
Steel construction:
Steel structures: AS 4100.
Cold-formed steel structures: AS/NZS 4600.
Residential and low-rise steel framing: NASH Standard – Residential and Low-Rise Steel Framing Part 1 or Part 2.
Composite steel and concrete: AS/NZS 2327.
Aluminium construction: AS/NZS 1664.1 or AS/NZS 1664.2.
Timber construction:
Design of timber structures: AS 1720.1.
Timber structures: AS 1684.2, AS 1684.3 or AS 1684.4.
Nailplated timber roof trusses: AS 1720.5.
Piling: AS 2159.
Glazed assemblies:
The following glazed assemblies in an external wall must comply with AS 2047:
Windows excluding those listed in (ii).
Sliding and swinging glazed doors with a frame, including french and bi-fold doors with a frame.
Adjustable louvres.
Shopfronts.
Window walls with one piece framing.
All glazed assemblies not covered by (i) and the following glazed assemblies must comply with AS 1288:
Skylights, roof lights and windows in other than the vertical plane.
Sliding and swinging doors without a frame.
Windows constructed on site and architectural one-off windows, which are not design tested in accordance with AS 2047.
Second-hand windows, re-used windows and recycled windows.
Heritage windows.
Glazing used in balustrades and sloping overhead glazing.
Termite Risk Management: Where a primary building element is subject to attack by subterranean termites: AS 3660.1, and—
for the purposes of this provision, a primary building element consisting entirely of, or a combination of, any of the following materials is considered not subject to termite attack:
Steel, aluminium or other metals.
Concrete.
Masonry.
Fibre-reinforced cement.
Timber — naturally termite resistant in accordance with Appendix C of AS 3660.1.
Timber — preservative treated in accordance with Appendix D of AS 3660.1; and
a durable notice must be permanently fixed to the building in a prominent location, such as a meter box or the like, indicating—
the termite management system used; and
the date of installation of the system; and
where a chemical is used, its life expectancy as listed on the appropriate authority's pesticides register label; and
the installer’s or manufacturer’s recommendations for the scope and frequency of future inspections for termite activity.
Roof construction (except in cyclonic areas):
Terracotta, fibre-cement and timber slates and shingles: AS 4597.
Roof tiling: AS 2050.
Cellulose cement corrugated sheets: AS/NZS 2908.1 with safety mesh installed in accordance with AS 1562.3 clause 2.4.3.2 except for sub-clause (c)(vii) for plastic sheeting.
Metal roofing: AS 1562.1.
Particleboard structural flooring: AS 1860.2.
Garage doors and other large access doors in openings not more than 3 m in height in external walls of buildings determined as being located in wind region B2, C or D in accordance with AS/NZS 1170.2: AS/NZS 4505.
Lift shafts which are not required to have an FRL, must—
except as required by (ii), be completely enclosed with non-perforated material between the bottom of the pit and the ceiling of the lift shaft, other than—
at landing doors, emergency doors and pit access doors; and
in atriums and observation areas, be protected with non-perforated material not less than 2.5 m in height—
above any places on which a person can stand, which are within 800 mm horizontal reach of any vertical moving lift component including ropes and counterweights; and
at the lowest level of the atrium area that the lift serves, on all sides except the door opening, for not less than 2.5 m in height, by enclosure with non-perforated material; and