TLDR - have you heard whether building over a main sewer pipe (with required water company approvals) causes rat problems?
Long version: We had been planning a 2.5m kitchen extension. We really didnt want to go out 3m as we are already concerned about the loss of garden (small London end of terrace property) but the drain survey shows the Thames sewer pipe running exactly along where the new foundation would go, so we cannot keep going with our existing plan.
The architect and builder are pushing us to go to 3m to avoid the drain, but we are concerned about the loss of the garden for our young children and we have heard some horror stories about building over sewers and rat infestations. A family member in particular had an awful issue.
To satisfy the regs, it would mean only coming out 1.3m (the inner edge of the manhole is sat at 1.8m out from the existing back wall of the house) so really questionable if worth the hassle or only doing an internal reconfiguration rather than extension, which would be disappointing.
None of the builders flagged this rat issue and all seemed to think building over is fine as long as we get the required permissions from Thames. The manhole would move along the pipe from the back of our house to the side. We are one of the few houses on the road that hasn't done the kitchen extension but when you look across they are not all a uniform depth so I think the pipe is not necessarily in a straight line across the back of everyone's house.
So looking to the knowledgeable posters here. Has anyone heard about this being a problem? Is it common knowledgeable? I absolutely HATE rats and have two DC under 5 so I do not want to create trouble. We know there are rats locally because a) its London and b) weve seen them around a derelict property on a road that backs onto ours (although further down the street than us). We have a healthy local fox population that helps keep them at bay outside but I do not want to risk them coming into the house if we can avoid it.