The problem is part Part of bathroom had been built on top of a precast concrete lintel wmanhole and not off a foundation and the invert level at 1.25. Wanted to know what to do

Hi, well i think you could do with calling the council, and getting one of there engineers- surveyor out to have a look wont cost a lot and you will know what needs to be done best wishes colin.

I think what you are saying is a proerty wall is built over a manhole. The lintel could well be substantial to carry the load. The problem sound like access to the manhole. Answer is to build another manhole alongside outside the building then break through to the existing thus enlarging for access to the main drain run and it`s branches off. Hope this helps.