NCC 2019 Volume Two
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Part 3.1.1 Earthworks

Part 3.1.1 Earthworks

Appropriate Performance Requirements

AppropriatePerformance Requirement:

Where an alternative approach to earthworks is proposed as a Performance Solution to that described in Part 3.1.1, that proposal must comply with—

  1. Performance RequirementP2.1.1; and
  2. the relevant Performance Requirements determined in accordance with A2.2(3) and A2.4(3) as applicable.

Explanatory information:

Explanatory information:

The provisions in Part 3.1.1 will enable earthworks associated with the construction of a building to be carried out safely and to avoid potential damage to the subject building, adjoining structures and property through the soil collapsing or subsiding. Exceptional site conditions (including the effects of torrential rain) may need special consideration and additional advice from appropriately qualified people should be considered.

State and Territory legislation may also have requirements that apply to earthworks, especially in relation to adjoining property and notification of owners of that property. Advice should be obtained from the appropriate authority before commencement of works.

The requirements of this Part are to be read in conjunction with Part 3.1.2 where an earth retaining structure is installed.

State and Territory Variations

State and Territory Variations

Except for Table 3.1.1.1 as refrenced by Figure 3.1.3.1 and except for Clause 3.1.1.0(a) for determination of a normal site as referenced by Clause 3.2.1, Part 3.1.1 does not apply in New South Wales.

Note: In New South Wales requirements for shoring and adequacy of excavation works are a prescribed condition of development consent. In addition consent authorities can place specific controls on siteworks associated with the construction of a building, by imposing further conditions of development consent. Information addressing siteworks can be found in the Department of Planning and Environment - Act and Regulation note "Health, safety and amenity during construction".

Acceptable Construction Practice

3.1.1.0 Application

Compliance with this acceptable construction practice satisfies Performance Requirement P2.1.1 for earthworks associated with the construction of a building or structure provided—

(a)

the site is classified as A, S, M, H or E in accordance with Part 3.2.4 and the work is undertaken in normal site conditions; and

(b)

un-retained bulk earthworks are undertaken in accordance with 3.1.1.1 and 3.1.1.2; and

Explanatory information:

Explanatory information:

"Normal" site conditions relates to parameters such as—

  • the site conditions not being significantly modified by the removal of previous buildings or other structures; and
  • the moisture conditions on site being as a result of seasonal and climatic changes; and
  • the site conditions not being subject to unusual moisture conditions caused by drains, dams, channels, ponds or tanks which are to be maintained or removed; and
  • large trees have not been recently removed from the site in the area where the building is to be constructed; and
  • other similar matters.

Further information regarding normal and abnormal site conditions can be found in AS 2870.

Table 3.1.1.1 Un-retained embankment slope ratios

Soil class

(see Part 3.2.4 for material description)

 Site cut (excavation)
(maximum embankment
slope ratio, angle of site cut
H:L Note 1)		 Compacted fill
(maximum embankment
slope ratio, angle
of batter H:L Note 1)
Stable rock ( Class A) 8:1 3:3
Sand (Class A) 1:2 1:2
Firm clay (Class M-E) 1:1 1:2
Soft Clay (Class M-E) 2:3 Not suitable

Notes to Table 3.1.1.1:

  1. See Figure 3.1.1.1 for some examples of un-retained embankment slopes.
  2. Retaining walls must be installed in accordance with Part 3.1.2 where—
    1. the embankment slope is steeper than described in this Table; or
    2. the soil type is not described in this Table.

Figure 3.1.1.1a Site cut and fill using un-retained embankments - Site cut commencing at the allotment boundary or affecting an adjoining property

v2_Fig3111a_2019.svg

Figure 3.1.1.1b Site cut and fill using un-retained embankments - Fill commencing at the allotment boundary or affecting an adjoining property

v2_Fig3111b_2019.svg

Notes to Figure 3.1.1.1b:

  1. The angle for line A-A is defined as the maximum embankment slope ratio H:L in Table 3.1.1.1 and is taken from the bottom of the existing footing and is defined as the area suitable for excavation.
  2. Consideration must be given for drainage of surface water, particularly where fill affects an adjoining property.

3.1.1.1 Un-retained bulk earthworks - site cut

A site cut using an un-retained embankment must be—

(a)

within the allotment; and

(b)

not within the zone of influence of any existing structure on the property, or the allotment boundary as defined in Table 3.1.1.1 and Figure 3.1.1.1a; and

(c)

not deeper than 2 m from the natural ground level at any point.

3.1.1.2 Un-retained bulk earthworks - fill

Fill, using an un-retained embankment must—

(a)

be placed within the allotment; and

(b)

be placed at a gradient which complies with Table 3.1.1.1 and Figure 3.1.1.1b; and

(c)

be placed and mechanically compacted in layers not more than 150 mm; and

(d)

be not more than 2 m in height from the natural ground level at any point; and

(e)

where used to support footings or slabs, be placed and compacted in accordance with Part 3.2; and

(f)

have surface water diverted away from any existing structure on the property or adjoining allotment in accordance with 3.1.3.3.