Do you need a build over agreement?
- Yes, if you are building over or within 3 m of a public sewer or a drain shared with neighbours
- Usually not, if the drain only serves your own property and stays within your boundary
- Check first using the water company's sewer map, a drainage search (CON29DW) or a CCTV drain survey
How to apply
- Find out which water company covers your area (Severn Trent covers much of the East Midlands)
- Confirm the route, depth and condition of the sewer, usually with a CCTV survey
- Submit drawings of the extension and drainage to the water company
- Pay the application fee and wait for approval before starting work
- Build to the agreed conditions, such as access points or protective lintels
Costs and timescales
Water companies charge an application fee, often from a few hundred pounds, with more for complex sites. Approval can take anything from a couple of weeks to a few months, so apply early. Budget separately for any survey or diversion work the water company asks for.
What if you've already built over a sewer?
It often comes up when selling. Buyers' solicitors may ask for evidence of consent. Options include a retrospective application, a CCTV survey to show the sewer is in good condition, or indemnity insurance. See our guide to drainage and water searches (CON29DW).
Can you move a drain instead?
Sometimes diverting the sewer around the extension is simpler than building over it. Diversions need water company approval and are usually more expensive, but they keep access clear for the future.
Read our full guide to building over a drain, or see our drainage groundworks service.