Thames Water Manhole in Back Garden – Do You Need Build Over Agreement?

Imagine this: You’re all set to build your dream extension, only to discover a Thames Water manhole lurking in your garden, threatening to derail your plans. Sounds like a nightmare, right? You’re not alone. In fact, Thames Water manages over 100,000 kilometers of public sewers, many of which run through private properties. But here’s the kicker – ignoring that manhole could cost you your entire extension. Let’s dive into the world of Build Over Agreements and uncover how you can turn this potential roadblock into a stepping stone for your home improvement journey.

Table Of Contents

What is a Build Over Agreement?
Do You Need a Build Over Agreement?
Why is a Build Over Agreement Crucial?
How to Get a Thames Water Build Over Agreement
Build Over Agreement Specifications
Cost of a Build Over Agreement
FAQs About Build Over Agreements

What is a Build Over Agreement?

A Build Over Agreement is a formal approval from Thames Water, certifying that your proposed construction won’t harm their sewer system. Without this agreement, your entire project could be at risk — halted mid-construction or, in the worst-case scenario, ordered to be torn down.

Do You Need a Build Over Agreement?

You’ll need a Build Over Agreement if:

You’re building within 3 metres of a public sewer or lateral drain
Your construction is within 1 metre of where a private pipe crosses your property boundary
You’re planning to build over a manhole (yes, it’s possible!)

Pro Tip: Check your property’s title deeds or consult a surveyor to identify any public sewers on your land.

Thames Water Manhole Build Over Agreement

Why is a Build Over Agreement Crucial?

Skipping the Build Over Agreement is like playing Russian roulette with your extension. Here’s why it’s non-negotiable:

Legal Compliance: Building Control officers may refuse to sign off your work without it.
Structural Integrity: Ensures your extension won’t damage the sewer or vice versa.
Future Access: Guarantees Thames Water can maintain the sewer if needed.
Property Value: A proper agreement can prevent issues during future property sales.

How to Get a Thames Water Manhole Build Over Agreement

Here is the information required to secure Thames Water Manhole Build Over Agreement:

Prepare Drawings: Create detailed plans showing your extension and sewer locations.
Identify Sewer Class: Determine the sewer size (Class 1, 2, or 3).
Complete Application: Fill out Thames Water’s Build Over Application form.
Submit Documents: Include site plans, cross-sections, and flow directions.
Pay Fee: Submit the appropriate fee based on sewer class.
Wait for Approval: Thames Water will review and respond to your application.

Thames Water Manhole Build Over Application Process (Image Credit: www.thameswater.co.uk)

For all three classes, you’ll need to upload the following:

Drawings of the Extension: Clearly show the location of the sewers and manholes, including the direction of the sewer flow.
Site Location Plan: Include this to indicate where your property and the sewer are situated.
Manhole Relocation Plans: If you need to move a manhole, the new location must be clearly shown, especially if it’s within 1.5 meters of your property.
Cross-Section of Foundations: Show how the foundations relate to the pipes if building close to a sewer.

Thames Water’s role doesn’t end at approval; they’re also responsible for the ongoing maintenance of public sewers and lateral drains. For private drains, however, the responsibility lies with the property owner.

Key Specifications for Build Over Agreement

Thames Water has strict criteria for approving Build Over Agreements. Key specifications include:

The application is not for a new dwelling
The proposed structure will not require building over more than 6 meters of the sewer
Minimum 150mm clearance between foundations and sewers up to 1.1m deep
Foundations must be at least 1.2 meters from the sewer if running parallel
No building over manholes or inspection chambers
Compliance with Water UK’s Design and Construction Guide

Remember: These specifications ensure both your extension and the sewer system remain safe and accessible.

Cost of a Build Over Agreement

A table showing Build Over Agreement costs based on sewer class

The cost of your Build Over Agreement depends on the sewer class:

Class 1 (≤150mm diameter): £105
Class 2 (151-375mm diameter): £445
Class 3 (>375mm diameter): £535 + additional legal costs
Note: Prices are subject to annual review. Check Thames Water’s website for the most current fees.

FAQs About Thames Water Manhole Build Over Agreements

Q: Can I build over a manhole? A: Yes, with proper approval and possibly relocating the manhole.
Q: What if I’ve already built without permission? A: Contact Thames Water immediately to discuss rectification options.
Q: Do I need a new sewer connection for my extension? A: Not necessarily, but you may need a Build Over Agreement.
Q: How long does the approval process take? A: Typically 2-4 weeks, depending on the complexity of your project.

Securing a Build Over Agreement is not just a bureaucratic hurdle; it’s a vital step in protecting both your property and Thames Water’s infrastructure. By following the guidelines and obtaining the necessary permissions, you can move forward with your home extension project with confidence, knowing that your work is compliant and your investment is secure.

If you’re unsure about any part of the process, consult a professional or reach out to Thames Water directly. Don’t let a small oversight lead to significant setbacks—ensure your project is on the right track from the start.

Ready to tackle that Thames Water manhole in your garden? Don’t let it flush your extension dreams away! Contact our extension experts today for a free consultation on navigating the Build Over Agreement process.