An extension, a new patio, or a garden room can easily end up sitting directly over or alongside a drain run without the homeowner realising until something goes wrong. UK building regulations have specific rules about building near drains precisely because pipework that isn’t properly protected, or that’s built over incorrectly, can lead to expensive problems later.
Why it matters
Building work near or over a drain can crack pipework under the weight of new foundations, block access for future maintenance, or interfere with the fall of the pipe, which affects how well it drains. None of this tends to show up immediately. It’s often only when a blockage becomes hard to clear, or a CCTV survey is needed, that the problem is traced back to work done years earlier.
What Building Regulations Part H expects
Part H of the Building Regulations covers drainage and waste disposal, and sets out minimum distances and protective measures for building near drains, including requirements around bridging foundations over pipework and maintaining access for inspection and repair. Your local authority building control team, or an approved inspector, will check this as part of any extension or major patio project.
Practical points to check before you start
- Get an up to date drainage plan, or arrange a CCTV drain survey if you don’t have one, so you know exactly where pipework runs
- Check whether any drain crosses the footprint of the planned extension or patio
- Confirm with building control whether bridging or protective measures will be needed
- Don’t assume a drain that isn’t visible above ground isn’t there
Soakaways need the same care
If your project includes new paving or hard standing, you may also need a soakaway to manage rainwater run-off, particularly under sustainable drainage requirements. Positioning a soakaway too close to a building or an existing drain run can cause its own problems. Our guide to soakaways covers what’s involved.
Getting this checked before the foundations go in is far cheaper than digging up a finished patio or extension later. If you’d like a survey before your project starts, call us on 0333 200 1623 and we’ll help you understand what’s under your garden.