Drainage under a continuous village terrace is rarely arranged the way anybody would arrange it today, and finding out how it actually runs is the first job.
Where houses were built as a run rather than individually, the drainage was usually laid as a run too. A single line frequently serves several properties, passing under gardens and through walls that were built around it, and the manhole in your garden may be the only access for a system serving your neighbours as well. That changes what can be built over, what can be diverted, and crucially who has to agree to it.
At the front there is a different complication. With the building on the footpath, rainwater from the front roof slope discharges at the edge of the public highway, often into a gully that is the county’s rather than yours, or into one whose ownership nobody has established in living memory. Before altering anything at the front we work out what belongs to whom, because getting that wrong turns a small job into a highways matter.
On a system of this age we put a camera down before designing over anything. An hour with a survey turns assumptions into a drawing.
Our drainage work page covers surveys, repairs and new connections.