Drainage & Sewer Compliance · London

Build Over Agreements

Building over or near a public sewer? We prepare the drawings, design the foundations and handle water-authority liaison to approval.

The basics

What is a Build Over Agreement?

A Build Over Agreement is a legal contract required when building over or near a public sewer, drain or utility. It's typically needed when an extension or development sits above or adjacent to underground infrastructure — ensuring construction doesn't obstruct or damage existing utilities, and setting out maintenance responsibilities between the owner and the utility provider.

Why it matters

Why a Build Over Agreement is Important

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Protection of Utilities

Safeguards public sewers, drains and utility lines so they remain functional and accessible for repairs.

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Compliance with Regulations

Building over a sewer without the right agreement is often illegal — this keeps you compliant and avoids fines.

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Preventing Future Problems

Clear guidelines on management, maintenance and future repairs help prevent disputes down the line.

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Ensuring Safe Construction

Proper permissions ensure work protects both your structure and the infrastructure beneath it.

When you need one

When is a Build Over Agreement Needed?

Public Sewers

If building directly over or near a public sewer, an agreement ensures it can still be accessed for maintenance and repairs.

Private Drains & Sewers

If your construction impacts private drains serving neighbouring properties, the agreement clarifies upkeep responsibilities.

Utility Lines

Water, gas or electricity lines beneath the property may need special consideration to stay protected during construction.

The process

How to Obtain a Build Over Agreement

Consult Local Authorities

Contact your local water/utility company early — in the UK this is usually your local water company.

Submit Detailed Plans

Provide plans showing the location of existing sewers, drains or utilities and how the build interacts with them.

Provide Documentation

Details of the construction, how you'll protect the utilities, safety measures and proof of property ownership.

Review & Approval

The authority assesses whether the project interferes with utilities and complies with regulations, then issues the agreement.

Compliance During Construction

Work is carried out in line with the agreement, with extra precautions to protect the sewer or drain.

What's covered

What to Expect in a Build Over Agreement

Location of existing infrastructure — maps and diagrams of the sewer, drain or utility beneath the site.
Construction restrictions — limits on heavy structures or deep foundations directly over the infrastructure.
Maintenance & access rights — who maintains the utility and how access for repairs is provided.
Repair & modification guidelines — how future repairs are handled so the utility stays functional.
Structural integrity requirements — design requirements so the build doesn't damage or obstruct the utility.

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Good to know

Build Over Agreement FAQs

What is a Build Over Agreement?

A legal contract required when constructing over or near existing public or private infrastructure such as sewers, drains or utility lines — ensuring construction doesn't obstruct or damage them and outlining maintenance responsibilities.

When do I need a Build Over Agreement?

If your project involves building over or near public sewers or drains, private drains serving neighbouring properties, or utility lines (water, gas, electricity) running beneath your property.

How do I apply for one?

Consult your local water company to understand requirements, submit detailed plans showing existing infrastructure and how your project may impact it, and provide documentation such as proof of ownership and structural details. We handle all of this for you.

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