Thames Water build-over agreement CCTV surveys for London extensions and basement conversions — pre-work condition survey and post-build check, produced to the standard required by Thames Water for structures built over or close to adopted public sewers.
Free, no-obligation — we'll call you back fast.
A Thames Water build-over agreement is required whenever you build a structure — extension, outbuilding, basement, or driveway — within 3 metres of an adopted public sewer. The agreement protects the sewer from damage and ensures Thames Water can access it for maintenance and emergency repair without demolishing your new structure. To obtain the agreement, Thames Water requires a pre-build CCTV drain survey confirming the current condition of the affected sewer, along with structural drawings from your architect showing the relationship between the proposed structure and the sewer run. We produce the CCTV drain survey report to the standard Thames Water accepts, formatted with the WRCm defect grading and pipe-condition assessment their technical team requires for a straightforward approval. In addition to the pre-build survey, Thames Water will typically require a post-build CCTV survey confirming the sewer has not been damaged during construction. Therefore, we work with architects and structural engineers throughout the London build-over process, supplying both the pre-build and post-build reports under a single agreed cost. As a result, London homeowners and developers avoid the frustrating back-and-forth of submitting inadequate reports — ours are accepted by Thames Water's technical reviewers first time, consistently. We also advise on whether your specific project requires a formal build-over agreement or falls within the lighter-touch build-near process, which applies to structures between 3 and 5 metres from the sewer. Many London extensions qualify for build-near, which carries a lower reporting burden and faster Thames Water approval.
Identify the affected Thames Water sewer from drainage records and site inspection
Pre-build CCTV survey — condition assessment of the sewer to WRCm standard
Report prepared and formatted to Thames Water build-over agreement submission requirements
Support for the Thames Water application submission if required
Post-build CCTV survey on completion — confirms no construction damage to the sewer
Post-build report delivered to close out the Thames Water agreement
Build over agreement CCTV surveys in London are priced by scope — a pre-build survey and report alone costs less than a combined pre-build and post-build package (both surveys plus both reports). All reports are produced to Thames Water submission standard. Request a fast, fixed-price quote online.
Thames Water requires a pre-build CCTV drain survey report confirming the current condition of the affected public sewer, produced to WRCm grading standards. They also require structural drawings from your architect or structural engineer showing the relationship between your proposed structure and the sewer, and a method statement confirming how the sewer will be protected during construction. We produce the CCTV survey report to the standard Thames Water accepts.
No — a build-over agreement applies when your structure is within 3 metres of a public sewer or directly above it. A build-near agreement applies when the structure is between 3 and 5 metres from the sewer. Build-near carries a lighter reporting requirement and faster Thames Water approval. We can advise which applies to your project based on your architect's drawings and the sewer position.
Thames Water typically takes 4–6 weeks to review and approve a build-over agreement application. Submitting a complete application with a properly-formatted CCTV survey report from the outset is the most effective way to avoid delays. Incomplete applications or survey reports that do not meet Thames Water's technical standard are the most common cause of rejection and resubmission delays.
No. Work must not begin until Thames Water has issued written approval of the build-over agreement. Starting work without approval is a breach of the Water Industry Act 1991 and may require you to demolish the structure at your own cost. We always advise obtaining the agreement before any groundworks begin.