1. Sydney’s unique geology, comprising a range of material from loose sand and weathered sandstone to shale and reactive clays, throws up design and construction challenges. Heavy excavation works throughout the city and surrounds occasionally fail those challenges, giving rise to litigation between, typically, developers and others involved in the excavation works, and neighbouring land owners.
2. Prior to legislative amendments in 2000 pursuant to which section 177 of the Conveyancing Act 1919 (NSW) was introduced (s177), if a landowner, in the course of excavation, undermined the support for the neighbour’s land, there was an “actionable nuisance for which strict liability attaches without proof of any negligence”: Fennell v Robson Excavations Pty Ltd  2 NSWLR 486 at 493 per Glass JA.
3. The right in common law to bring an action in nuisance is abolished by s177, which substitutes a statutory duty of care “not to do anything in relation to … the supporting land … that removes the support provided by the supporting land to any other land.”
4. That duty, and the qualifications thereto, have been considered in a handful of cases.
5. The object of this paper is to provide a short outline of the jurisprudence regarding the duty of care owed in respect of adjoining land that has built up around s177 of the Conveyancing Act 1919 (NSW). In the course of that discussion, some of the issues thrown up by the application of the legislation to the factual circumstances that the courts have been required to address are considered.