What this job actually involves Pre-extension drain survey — how it works here
Building over or near a drain is allowed, and it is done constantly in north Warrington. What causes trouble is doing it without knowing what is down there: a run that was already failing gets buried under a new room, a chamber gets covered rather than relocated, and the problem surfaces two years later under a floor you cannot lift.
- The run traced and marked on the ground before anything is dug
- Depths recorded, which your builder needs for foundations and your building inspector will ask for
- Existing condition documented — so a defect that was already there does not become your builder's dispute
- Chambers located, including any that have already been covered by earlier work
- Shared lengths identified, because building over a run that serves neighbours is a different conversation
- Written and dated, which is what makes it useful if anything is questioned later