Securing Planning Permission Without the Headache
Adding an extension, conservatory, or new outbuilding to your property is an exciting project. However, if your planned construction falls within three metres of a public sewer, you are legally obligated to obtain a formal "build-over agreement" from your local water authority (typically Thames Water or Southern Water in the Surrey area) before any work can commence.
At Clever Works, we specialize in providing the precise, highly detailed CCTV drainage surveys and technical documentation required to satisfy water authority regulations. We take the stress out of the compliance process, ensuring your architect and builder have exactly what they need to keep your project moving forward without costly delays.
What Does a Build-Over Survey Involve?
A build-over agreement exists to protect the public sewer network. The water authority needs absolute proof that your new structure will not crush or damage their pipes, and that they will still be able to access the sewer for future maintenance.
To provide this proof, a specialized CCTV drainage survey is mandatory. We insert high-definition cameras into the drainage system to map the exact location, depth, diameter, and structural condition of the sewer lines crossing your property. We then generate a comprehensive, WRC-approved report. This report, alongside your architectural drawings, forms the basis of your application. Once your extension is built, a secondary "post-build" survey is required to verify that the sewer remains undamaged by the construction work.
Why Choose Clever Works for Your Survey?
Water authorities are notoriously strict about the format and quality of the evidence they accept. A generic camera inspection from a standard plumber will almost certainly be rejected, causing frustrating delays to your build schedule.
Clever Works utilizes industry-leading WinCan reporting software to produce WRC-approved CCTV surveys. This is the exact standard demanded by Thames Water. With over 10 years of experience and 550+ surveys completed, we know exactly what the planning departments are looking for. Furthermore, as a SafeContractor accredited and BSI tested company, you can trust that our data is accurate, reliable, and professionally presented.
What to Expect: The Agreement Process
Pre-Build CCTV Survey
Before any foundations are dug, our engineers attend your property to map the sewer lines, assess their condition, and produce the initial WRC-approved report.
Application Submission
You (or your architect) submit our detailed reports, site plans, and video footage to the local water authority alongside your building plans.
Construction Phase
Once the water authority grants the build-over agreement, your builders can safely construct the extension following the agreed-upon guidelines.
Post-Build Verification
Upon completion of the building work, we return to conduct a final survey, proving the sewer is intact so the authority can issue the final sign-off.
Build-Over Surveys in Farnham & Surrey
Farnham and the surrounding Surrey towns—including Guildford, Godalming, and Haslemere—are characterized by a dense mix of historic properties and mid-century housing estates. As homeowners increasingly choose to extend rather than move, build-over agreements have become a standard part of local planning applications. The drainage infrastructure in these areas is often a complex web of shared sewers that were transferred to Thames Water's ownership in 2011. Many homeowners are unaware that the pipe running under their patio is actually a public sewer until their architect informs them. Clever Works has extensive experience navigating the specific requirements of Thames Water and Southern Water, ensuring homeowners across Surrey can proceed with their extensions legally and safely.
Frequently Asked Questions
Do I always need a build-over agreement?
If your planned extension, conservatory, or new outbuilding is within 3 metres of a public sewer, yes. It is a strict legal requirement. If you build without one, the water authority has the statutory right to tear down the structure to access their pipes.
What happens if I don't get one?
Building without an agreement will cause major issues when trying to sell your property, as the buyer's solicitor will request the documentation. You may also be held financially liable for any damage caused to the public sewer by your foundations.
How long does the CCTV survey take?
A standard pre-build CCTV drainage survey for a residential property usually takes between 1 to 2 hours on site. We process the data and provide the comprehensive WRC-approved reports and footage shortly after completion so you can submit your application without delay.
Can you guarantee Thames Water will approve it?
While we cannot guarantee the final approval (as that depends on the specifics of your architectural plans and foundation design), we absolutely guarantee that our CCTV drainage survey reports meet the strict WRC standards required by Thames Water and all other UK water authorities.