NCC 2022 Volume One - Building Code of Australia Class 2 to 9 buildings
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4

Specification 4 Design of buildings in cyclonic areas

Specification 4 Design of buildings in cyclonic areas

(1) This specification contains requirements for the design of buildings in cyclonic areas in addition to the requirements of AS/NZS 1170.2.

(2) For the purposes of Specification 4, cyclonic areas are those determined as being located in wind regions C and D in accordance with AS/NZS 1170.2.

WA S4C1 Scope2019: Spec B1.2: 1

Delete subclause S4C1(2) and insert S4C1(2) as follows:

(2) For the purposes of Specification 4, cyclonic areas are those determined as being located in wind Regions B2, C and D in accordance with AS/NZS 1170.2.

Test for strength: Metal roof cladding, its connections and immediate supporting members must be capable of remaining in position notwithstanding any permanent distortion, fracture or damage that might occur in the sheet or fastenings under the pressure sequences A to G defined in Table S4C2.

Table S4C2 Low-high-low pressure sequence
Sequence Number of cycles Load
A 4500 0 to 0.45 Pt
B 600 0 to 0.6 Pt
C 80 0 to 0.8 Pt
D 1 0 to 1.0 Pt
E 80 0 to 0.8 Pt
F 600 0 to 0.6 Pt
G 4500 0 to 0.45 Pt
Table Notes
  1. Pt is the ultimate limit state wind pressure on internal and external surfaces as determined in accordance with AS/NZS 1170.2, modified by an appropriate factor for variability, as determined in accordance with Table B1 of AS/NZS 1170.0.
  2. The rate of load cycling must be less than 3 Hz.
  3. The single load cycle (sequence D) must be held for a minimum of 10 seconds.
NCC Blurbs

(1) Where a residential building of Class 2, 3, 9a or 9c, in Region C as defined by AS/NZS 1170.2, is designed to be used by the Aged or Infirm it shall incorporate a “strengthened area” for use as shelter during cyclonic conditions and must comply with the following criteria:

  1. The floor area of the “strengthened area” is to be calculated at the rate of 1.2 m2 per person normally accommodated within the building.
  2. The design wind pressure for the overall “strengthened area” is for an Importance Level 3 building.
  3. The minimum standard of debris protection to walls, floors and ceilings (or roof) bounding the "strengthened area" shall be that which resists (without complete penetration) the impact loading specified in AS/NZS 1170.2, using a regional wind speed associated with an Importance Level 3 building.
  4. All doors, windows, vents and the like in walls bounding the “strengthened area” are to be protected against windborne debris with permanently installed screens in accordance with (c).
  5. Consideration must be given to the selection of materials and fittings to ensure doors, windows and vents can withstand the required design wind pressures.
  6. All doors serving as required entries/exits to a “strengthened area” are to be inward opening with locking devices suitably noted for use in a cyclone emergency.

(2) The term “strengthened area” is defined as the strengthening of an area to increase its potential to facilitate debris protection.

NCC Title

Strengthened area

NCC State
NT
NCC Variation Type
Insertion
NCC SPTC Current
Strengthened area