NCC 2022 Volume Three - Plumbing Code of Australia
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E3

TAS Part E3 Stormwater - Roof drainage systems

TAS Part E3 Stormwater - Roof drainage systems

Introduction to this Part

This Part sets out the requirements for a roof drainage system.

TAS E3O1 Objective2019: F01

The objective of this part is to—

  1. safeguard people from illness, injury or loss (including loss of amenity) due to the failure of a roof drainage installation; and
  2. ensure that a roof drainage installation is adequate; and
  3. conserve water and energy; and
  4. safeguard the environment; and
  5. safeguard public and private infrastructure; and
  6. ensure that a roof drainage installation is designed and is capable of being maintained so that throughout its serviceable life it will continue to satisfy Objectives (a) to (e).

TAS E3F1 Functional statements2019: FF01

Buildings are to be provided with roof drainage to provide protection to people, property and the environment from adverse effects of stormwater.

TAS E3P1 Roof drainage systems2019: FP1.1

(1) A roof drainage system must have the capacity to transfer the volume of water anticipated in a 5% annual exceedance probability rainfall event.

(2) Box and valley gutters must have capacity to transfer the volume of water anticipated in a 1% annual exceedance probability rainfall event.

(3) The annual exceedance probability must be appropriate to—

  1. the importance of the building; and
  2. the severity of potential damage to the property; and
  3. The severity of loss of amenity, illness or injury that would result from the failure of the system.

TAS E3P2 Overflow2019: FP1.2

A roof drainage system must provide an overflow device suitable for a 1% annual exceedance probability rainfall event.

TAS E3P3 Watertightness2019: FP1.3

All internal roof drainage components must be watertight.

TAS E3P4 Design, construction and installation2019: FP1.4

(1) A roof drainage system must ensure that—

  1. stormwater is transferred to a Network Utility Operator's stormwater system or an approved disposal system; and
  2. appropriate access is provided for maintenance and clearing blockages.

(2) A roof drainage installation must avoid blockage and uncontrolled discharge causing—

  1. loss of amenity; and
  2. loss to building and property.

(3) A roof drainage installation must avoid foul air and gasses accumulating in the roof drainage system.

TAS E3D1 Application2019: F1.1

Performance Requirements E3P1 to E3P4 are satisfied by complying with E3D2 and E3D3.

TAS E3D2 General requirements2019: F1.2

A roof drainage system must comply with—

  1. AS/NZS 3500.3; or
  2. Housing Provisions 7.4

TAS E3D3 Roofing of liquid trade waste generation areas2019: H201.2

(1) When a liquid trade waste generating process does not fully occur within a building, suitable roofing must prevent the entry of stormwater to the disposal system.

(2) When a liquid trade waste generating process occurs within a building where one or more sides are open to the weather, a vertical overhang of a minimum of 10° from the roofing must be provided.

(3) Where the wind driven rainwater is likely to enter under the roof in extreme storm conditions, the roof must overhang by a minimum of 10° from the roofing.

Explanatory information

TAS Figure E3D3 provides an example of a suitable installation practice to meet the requirements of E3D3(3).

Insert TAS figure (E3D3 explanatory) E3D3 as follows:
TAS Figure E3D3 explanatory: Roofing of liquid trade waste areas
image-E3D3-roofing-of-liquid-trade-waste-areas-TAS.svg