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Extension - shared drains

My partner and I are in the process of buying a flat with a view to adding a side return to widen the bedrooms. I don't know for sure, but suspect that there are shared drains under the area where we would like to extend.

From doing some googling, it seems like the options are:
1. Ensure that the extension doesn't cover the manhole cover, which leaves for an oddly shaped extension
2. Extend and just cover the manhole cover (with access through floor?), which feels fairly risky in case of overflow/blockage
3. Move the drains - can anyone provide a ballpark figure for how much this could cost? It feels like the most preferable option, but not if it will cost an additional £20k, and make the extension unviable.

I realise there are lots of unknowns but any general advice would be great.

Cheers, Anna

2 Answers from MyBuilder Extension Builders

Best Answer

You can build over the drain and put a double sealed cover in the new floor. This will stop any risk of smells or overflow. But obviously if there was a problem you would need to allow access. Not nice in a bedroom. Or you can move the inspection chamber to outside the extension assuming there is room. This would be my preferred method. If the chamber is plastic this could be moved very easily and for little cost. (mostly labour charges for the digging and a few fittings and pipe as you would be able to reuse the existing chamber. If the chamber is brick then not only would you have the digging but the breaking down of the old chamber. (this can be time consuming) and the cost of new chamber, risers, cover, pipes and fittings. A couple of days labour and a few hundred on bits should cover it.


Answered 16th Nov 2017

The first reply from MK is exactly right, if you have enough room to the front, rear or side of the extension then move the chamber but if not the double sealed chamber cover is the alternative. Incidentally i do have a house with the double sealed chamber in a bedroom, you wouldn't even know it was there and there is access via a floor hatch.


Answered 17th Nov 2017

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