Hi we have recently had a rear extension built and have had the inspector come round after being on holiday and he has stated we need to expose the original manhole (I dont know if this leads on to the main drain, but is the only manhole on our property).
We were obviously shocked as we have laid membrane/joists/tiles etc and this would involve ripping out our showerroom floor to expose the original manhole.
This was never brought to our attention before and throughout the inspection nothing was mentioned and we thought therefore we could simply divert the drains etc from the old building and the new drains/wastes for the new extension to a new inspection chamber connected to the old drain which we have done.
If a blockage etc occurs then the inspection chamber is easily accessible. However the inspector is still insisting on seeing the old drain. Is he right?
The simple answer is yes you can build over a manhole cover. Im currently having a kitchen extension which is similar to your situation. I would be interesed myself in seeing what other poelpe think?.. Theres a few options of half sealing the old manhole up with cement or fitting a double sealed lid to the old manhole which still allows access. Im suprised your inspections or plans didnt pick up on this before.
The even simpler answer is no you cannot just build over manholes willy nilly and your architect or builder is hugely at fault for doing so. It is not the building inspectors responsibility to wander round your property trying to find all the things you should and should not do. It is your responsibilty to get the correct advice from architects and builders to keep your home safe. If there is, because of new drain installations, a build up of gas underground it can blow the extension to pieces, that why he wants to see it. Drains are dangerous which is why they are covered by the building regulations and you cannot just build over them without permision. This, as with all building regulations, is to keep you and any future owners of your house safe.
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