Drain Survey for a Home Extension: What You Need to Know in Yorkshire

# Drain Survey for a Home Extension: What You Need to Know in Yorkshire

Planning a home extension is one of the most exciting things you can do to your property — more kitchen, a bigger living room, a garden room. But before a single foundation is dug, there's one thing that catches Yorkshire homeowners off guard more than almost anything else: the drains.

A drain survey for a home extension isn't just useful — in many cases it's a legal requirement. And skipping it can stall your project, cost you thousands, or leave you unable to sell your home later. Here's what you need to know.

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Do I Need a Drain Survey Before Building an Extension?

Yes — in most cases. If your extension is being built within 3 metres of a public sewer or drain (or directly over one), you'll need a Build Over Agreement from Yorkshire Water before work can proceed. To apply for that agreement, Yorkshire Water typically requires a pre-construction CCTV drain survey to establish the current condition of the sewer.

Even if your extension isn't directly over a public sewer, Building Regulations Part H requires that new drainage connections and alterations comply with approved standards. Your building control surveyor will want to know the layout and condition of your existing drainage before signing off.

The bottom line: a drain survey is one of the first things to sort, not an afterthought.

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What Is a Build Over Agreement and Why Does It Matter?

A Build Over Agreement (BOA) is formal permission from your water authority — Yorkshire Water in this region — to build over or close to a public sewer. Under the Water Industry Act 1991, water companies have a legal right to access their sewers at any time. If you build over one without their agreement, they can require you to demolish what you've built, at your cost.

Yorkshire Water's BOA process requires:

• A CCTV drain survey of the affected sewer before work begins
• Submission of your proposed construction drawings
• A post-construction CCTV survey to confirm the sewer hasn't been damaged

Without a completed BOA, you may struggle to get building regulations sign-off — and when you eventually come to sell, your solicitor will ask for it. Missing paperwork can delay or even kill a house sale.

Almost 30,000 new homes across the UK have been stalled in recent years partly due to drainage and sewer complications — and that's on larger developments. For individual extensions, undiscovered drain problems are just as likely to derail timelines.

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What Does a Pre-Extension Drain Survey Actually Look For?

Our engineers use best-in-class iTouch CCTV cameras to inspect your drainage system before any groundworks begin. We're looking for:

• The exact position of drains and sewers — critical for your architect and structural engineer
• Existing damage — cracks, root ingress, displaced joints, or collapsed sections that could worsen during construction
• Pipe materials and condition — older Yorkshire properties often have pitch fibre or clay pipes that are already fragile
• Flow direction and connections — confirming which drains are foul, which are surface water, and where they connect

Most residential surveys take between one and three hours. You'll receive a full written report and recorded footage — exactly what Yorkshire Water and your building control surveyor need to proceed.

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Can I Build Over a Drain Without Knowing It's There?

More easily than you'd think — especially in older Yorkshire terraces and semis where drainage records are incomplete or inaccurate. Drains can run diagonally across gardens, through outbuildings, or at unexpected depths.

The only reliable way to know is a CCTV survey combined with a drain tracing exercise. We map the precise route of your drains on site, so your architect can design around them — or your solicitor can flag the issue before exchange if you're buying a property with extension potential.

This is also why a drain survey is valuable during a house purchase: a property with an unauthorised build-over or no BOA paperwork is a legal problem waiting to happen.

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How Far in Advance Should I Book a Drain Survey for My Extension?

Book early — ideally at the design stage, before your architect has finalised drawings. Knowing the drain layout can influence where your extension sits, its depth, and the foundation design.

Leaving the survey until your builder is on-site is a false economy. If the survey reveals a damaged sewer or an undocumented drain running exactly where your foundations are planned, you're looking at redesigns, delays, and potentially significant extra cost.

Booking ahead also gives you time to apply for the Build Over Agreement — Yorkshire Water can take several weeks to process applications — without it holding up your build programme.

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Book Your Pre-Extension Drain Survey

Yorkshire Drain Survey covers the whole of West and South Yorkshire, including Leeds, Bradford, Wakefield, Harrogate, and beyond. Our experienced engineers use professional iTouch CCTV camera equipment and provide detailed reports accepted by Yorkshire Water and building control teams.

Call 0113 734 2245 for a quote, or fill in our contact form and we'll get back to you promptly. We provide clear upfront pricing before any work begins — no hidden charges.

Getting your drains sorted before you break ground is one of the smartest decisions you can make on any extension project. Let's make sure your build goes smoothly from day one.