Build-over agreement

A build-over agreement is a formal consent issued by the sewerage undertaker, in Greater London usually Thames Water, allowing building works to be constructed over, alongside or close to a public sewer or lateral drain. The agreement is required where Approved Document H4 thresholds are met, typically within 3 metres of a public sewer or where loadings could affect the pipe. The process includes review of the existing sewer condition, often via CCTV survey, design of any protective measures such as concrete encasement or relocation, and provision of access for future maintenance. Practical implications for homeowners include allowing six to twelve weeks for approval and budgeting for any required protection or relining of the sewer. The agreement supplements Local Authority Building Control approval and is not a substitute for either Building Control or planning permission.