PART H · Drainage and waste disposal
Can I build an extension over a sewer
An extension can sometimes be built over or near a sewer, but the answer depends on the sewer, the proposed work and the relevant undertaker's requirements. Building regulations approval and sewer permission are separate matters.
Is the pipe private or public
Do not decide ownership solely by whether the pipe lies within your garden. Obtain appropriate records and, where necessary, a survey of the actual route and connections.
A pipe shared with another property may need a different assessment from a drain serving only your own house. Ownership affects whom you must consult.
What does Part H require
Part H includes protection for relevant sewers when building work is carried out over or close to them. The design should avoid damaging the pipe or prejudicing access and use.
Ask the sewerage undertaker whether an agreement or other approval is needed. Its criteria may depend on pipe size, depth, location and the nature of the proposal.
What must the designer consider
The structural arrangement needs to account for the sewer and surrounding ground. Drain condition, foundation position and access for future maintenance can influence the detail.
For example, an inspection chamber within the proposed room should be identified before work is priced. It is not something to discover when the floor is being laid.
What should I do first
Obtain a measured drainage layout, check the undertaker's current requirements and coordinate the structural and drainage designs. Agree the necessary inspection and testing stages before covering the work.
Keep any agreement with the approved drawings and completion records. A contractor's assurance that they regularly build over drains is not a substitute for the correct permissions and design.
If diversion is proposed, establish the destination, land rights and approval route before treating it as a simple alternative.