If you’re planning on having an extension built at home, don’t just think how far it’ll go out into the garden, or how high the roof will be. Think about what it will go over. Before any building work can be started, you’ll need to consider what’s happening underground.
If the extension is within 3 metres of a public sewer, you’ll need to have a build over survey done, to get consent from the relevant water or sewerage company. (A “public sewer” is defined as any drainage that takes waste from more than one household.) And that applies to all work, even permitted developments where you might not need to get full planning permission. So that’s for conservatories, porches, or garages as well as house extensions.
Building over an existing drain or sewer poses a risk of damage, so you have to show how the builder will avoid any damage to these pipes. The water company will also need to continue to have access to any manholes for maintenance purposes. You’re not allowed to build directly over mains water pipes, existing manholes or drains – although you could possibly have any manholes relocated a little away from your extension.
The best way to determine the exact position and condition of the drains is to have Happy Drains carry out a CCTV survey. This will also help establish whether relocating a manhole is possible. It will also determine whether you are able to submit a self-certification declaration, or whether you need to have a build over agreement drawn up. For example if any of your pipes are larger than 150mm in diameter, made of pitch fibre, or there are manholes or inspection chambers within 500mm of the extension, then a build over agreement will be necessary.
Sounds complicated? It can be. And extensions are not cheap! So before anyone digs any trenches, seek some professional advice from an architect, your local planning office or water company… or just give us a call at Happy Drains on 0800 849 8099. We provide CCTV survey reports to the highest industry standards.
