Once you decide to undertake a side return extension project, one of the factors you will need to consider is whether any of the building work is being carried out near to a sewer. If you are planning to build over or close to a public sewer then you will need a written agreement from your sewerage undertaker. In the London area this is Thames Water.

 

Under building regulations, Thames Water requires anyone who is building over or within three metres of a public sewer to make an application for a Build Over agreement. This is to ensure that no damage is caused to the sewer and that the building work does not restrict how the sewer is used and maintained.

You can submit the application online, via the Thames Water website, or you can print out a form and send an application in the post. You will need to submit detailed plans, with the sewer clearly marked, showing its position in relation to the new structure. Foundation arrangements and manhole details will also need to be highlighted.

 

Please note that a Build Over application will need to be submitted in addition to a Building Regulations application.

Sewer flushers from the 19th century in the Fleet sewer below Farringdon Road, London

Sewer flushers from the 19th century in the Fleet sewer below Farringdon Road, London

 

Something to bear in mind is that there is a cost involved in making a Build Over agreement. How much this is will depend on the size of the sewer to be surveyed and whether a thorough investigation needs to be carried out.

 

Whilst your project is in the design and planning stages you might want to consider making some alterations to your plans if you find that they could affect a public sewer. A few modifications to ensure that the building work is at least three metres away from the sewer could save you a lot of money. Another option is for your sewage undertaker to divert the sewer, but keep in mind any work carried out will be at your expense.

 

Once you have applied for a Build Over agreement, you may be permitted to build over a sewer provided that it is in a satisfactory condition. Before work gets underway a CCTV survey will need to be carried out to determine whether the sewer needs any repairs. Once the work is finished, another survey will be conducted to ensure that no damage has occurred.

 

In order to avoid any problems, delays or unforeseen costs, it is essential to contact the sewage undertaker as early on in the design process as possible. If you have not obtained a Build Over agreement the sewage undertaker may have the right to insist that building work stops and any existing building may have to be dismantled. If you follow the right procedures, these problems should be eliminated. Don’t forget, here at Build Team we can assist you with the administration of a Build Over agreement should this be required.