We want to build a bathroom over an existing flat roof extension?

[milquetoast]

Any idea how much this would cost in London?

Looked at a place last month with an estate agent who recommended doing the same thing, and he said £10K. No idea if that's a little or a lot.

I think about 4k fir the structural work and then whatever bathroom you choose.

Thanks very. 10k is not so bad. I suppose that's without the furniture, tiles and all.

Wow, even better

You have to check if the existing extension can support another room on top.

It's needs to have been build with the support in place, or you will be in trouble.

We bought a house with a flat roof kitchen extension, and checked we could build another room on top before we bought. We then had a quote for one room to be build, and were told £20K. DH says he was having a laugh and thinks it would be more like £15K for a bedroom and an en suite.

That is a good point.

The proposed bathroom would be on the second floor. Ground floor is the original kitchen and there is a bedroom on the first floor. I believe the previous owner built the flat roof when they extended the kitchen side return, maybe not wanting water draining down on the kitchen's glass roof.