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 neighbor’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.

License agreements for access. Where scaffolding, tiebacks, crane swing or protection work require entry, a written license with compensation, insurance, indemnity, a schedule and a restoration obligation. Several states provide a court procedure where the neighbor refuses unreasonably.

Pre-construction surveys. Photographic and instrumented documentation of the neighbor’s structures before work begins, which is the only reliable defense 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 neighbor, and confirmation that the contractor’s policy covers this exposure.