Building close to a property line creates obligations to the adjoining owner that exist independently of any agreement.
Lateral support. A landowner has an absolute right to support of land in its natural state. Removing support and causing subsidence is actionable without proof of negligence. Where the neighbour’s land carries buildings, liability for damage to the structures generally requires negligence, though several statutes and ordinances impose strict duties for excavation below a specified depth.
Statutory notice. Many jurisdictions require notice to adjoining owners before excavation, with an obligation to protect their structures and, in some, a right of access to do so.
Licence agreements for access. Where scaffolding, tiebacks, crane swing or protection work require entry, a written licence with compensation, insurance, indemnity, a schedule and a restoration obligation. Several states provide a court procedure where the neighbour refuses unreasonably.
Pre-construction surveys. Photographic and instrumented documentation of the neighbour’s structures before work begins, which is the only reliable defence to a claim that pre-existing cracks were caused by the excavation.
Monitoring. Vibration and settlement monitoring with thresholds and a response protocol.
Insurance. Coverage naming the neighbour, and confirmation that the contractor’s policy covers this exposure.