The Western Cape High Court found that the common law duty to provide lateral support to a neighbouring property falls within the law of neighbours where the guiding principle is reasonableness. The duty of lateral support relates to contiguous pieces of land even where the land has been built on, provided the buildings have not unreasonably loaded the property so as to place a disproportionate or unreasonable burden on the neighbouring land.

The defendant in Dias v Petropulos excavated her property on the steeply sloping mountainside of Camps Bay next to the built-on property of the plaintiff causing lateral movement and subsidence damage to the neighbouring garden, swimming pool and main house of the neighbour. The court found that the plaintiff had not unreasonably loaded his property through the construction of a residential dwelling. The plaintiff had not forfeited his right to lateral support by unreasonably loading his land. The evidence established that the plaintiff’s property clearly moved laterally and downwards towards the excavation. The defendants owed the plaintiff a duty to provide lateral support and the appropriate order was made.

This lengthy and interesting judgment is a correct analysis of neighbour law. It was a necessary analysis because in English law lateral support is owed to land in its natural state only. Our law is based on neighbour law and not English law and reasonableness is the test. There is a very useful article on neighbour law by Milton in 1969 Acta Juridica.