Building over or near a public sewer
Reviewed October 2026 · Not legal, planning or financial advice
Many Irish houses, especially in terraces and older estates, have a public sewer or shared drain running across the back gardens. It is one of the most common causes of unexpected extension cost.
Why it matters
Building over or close to a public sewer requires consent from Uisce Éireann and may require the pipe to be protected, surveyed or diverted. A private drain serving only your house is usually simpler, but still needs design care.
What to do
- Find out where drains run — manholes in the garden are the clue.
- A CCTV drainage survey shows the route, depth and condition.
- Raise it with your architect early; it can change the footprint.
Regulations and their interpretation change. This guide explains the position as we understand it in October 2026. Confirm what applies to your house with an architect, planning consultant or your local authority before relying on it.