Industry Alert: Deep Excavation on or near a boundary

In most cases, these excavations are occurring within the ‘zone of influence’, as detailed within the Building Code of Australia (BCA) 2022 Volume Two, Part H1D3 and Housing Provisions Standard 2022 Part 3.2 [2019: 3.1.1.1].

These excavations are carried out for a variety of purposes; site cuts, footing excavation, basement construction, retaining wall installations etc.

They have undermined buildings on or near a boundary and caused soil instability at the adjoining property.

Building surveyors are specifically reminded of the requirements of Building Regulation 112(1)(d), (e) & (f) (amongst other matters) along with the Building Act 1993 definition of adjoining property, outlined below. 

112 Matters relevant building surveyor must consider when determining if protection work required

For the purposes of making a determination under regulation 111, the relevant building surveyor must have regard to—

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(d) any excavation required as part of the proposed building work; and

(e) any proposed building work in relation to party walls and retaining walls; and

(f) the nature and likely extent of any damage or other adverse effect on the stability or otherwise of an adjoining property that may be caused by the proposed building work; and

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adjoining property means land (including any street, highway, lane, footway, square, alley and right of way) which is so situated in relation to the site on which building work is to be carried out as to be at risk of significant damage from the building work.

In some instances, it may not have initially been envisioned that the adjoining property was at risk of significant damage, however building surveyors are reminded that Building Regulation 111(3) provides that the RBS may at any time determine that protection work is required in relation to building work.