Get Rapid Plans Ltd

Architectural Services

Phone: 07507 665812


Get Rapid Plans Ltd

Architectural Services

Phone: 07507 665812


Build Over Agreements

You need to do a build over agreement when you plan to construct or extend a building over or near a public sewer or drain on your property. 

This legal agreement is necessary to ensure that your construction complies with regulations from your local water authority (such as Thames Water) and safeguards the integrity of the public sewer system.

Performing a build over agreement is essential to avoid potential legal issues and penalties associated with unauthorized building over or close to public sewers.


By obtaining a build over agreement, you can proceed with your development project confidently, knowing that it is in compliance with local water authority regulations. Let us guide you through the process, maximizing your development potential and turning your vision into a reality.

What Do You Need for a Build Over Agreement?

To apply for a build over agreement, you’ll need the following:

Existing House and Drainage Layout Plans: Provide a plan showcasing your current house and drainage layout, indicating the positions of inspection chamber(s) and the sewer with the flow direction marked. 

Proposed Extension and Drainage Layout Plans: Submit a plan illustrating your proposed extension and drainage layout, highlighting the position of the sewer and inspection chambers. If the extension covers the sewer (building over it), indicate the location of any existing manhole to be replaced with a new chamber in the garden.

Site Location Plans: Include an outline OS type plan of the street, displaying your plot’s position concerning the road and neighboring buildings.

Cross Section Drawings (if applicable): If you’re building directly over the sewer or within 1.5m of it, provide a cross-section drawing. This drawing must clearly depict the new foundations relative to the sewer pipe and show how you intend to bridge over the pipe, such as using concrete lintels.

Get your build over agreement done fast with our experienced team. We’ll provide detailed drainage drawings that will shorten the process and save you unnecessary wait times.

Our team will liaise with the authority and deal with any of their queries promptly, allowing you to start construction ASAP.

Get Your Questions Answered With Expert Advice

Frequently Asked Questions

Do I Need a Build Over Agreement?

A Build Over Agreement is a mandatory requirement imposed by water companies for any construction work carried out over public sewers or within 3 meters of one. In some cases, this obligation is even incorporated as a covenant in the Deeds of newer properties.

Prior to commencing any building work on the site, approval from the water company must be obtained. However, there is a potential complication: even if a waste pipe exclusively serves your property and is classified as a private drain, some water companies may still insist on a Build Over Agreement if you intend to build within 1 meter of the boundary where the pipe exits on your land. It is advisable to verify this requirement with the respective water company.

This precaution is likely taken because any damage to the pipe on your property side could potentially lead to issues downstream for the water company. Complying with the Build Over Agreement ensures that construction activities do not pose a risk to the public sewer system and maintains the integrity of the overall drainage network. 

For further information, contact our experienced team now for free advice on your project.


How Much Time Does a Build Over Agreement Take?

Typically, applications for BOAs are processed efficiently, usually within a three-week timeframe. Upon receiving the agreement, you can typically commence your construction work. Any delays that may occur are often a result of incomplete submissions, such as missing drawings or essential information.

Ensuring comprehensive and accurate documentation will help expedite the approval process, allowing you to proceed with your project without unnecessary hold-ups. We provide detailed drainage drawing that will 

What Happens After the Agreement Has Been Made?

After obtaining the agreement from the water company, building control will conduct regular site inspections throughout the construction phase, closely monitoring the drainage provision to ensure compliance and smooth progress.

Divi Home

At Divi we understand that your home is your sanctuary, and we’re here to help you bring your vision to life. With our exceptional quality, timeless designs, and personalize customer service, we strive to exceed your expectations every step of the way.