We have just bought a one bed coach house above 3 single garages. We own the first garage (and are the freeholders of the whole building) and the previous owner has half converted it into an extra bedroom. When I say 'half converted' he has insulated the floor and walls, plastered, painted, added skirting boards, proper lighting and sockets etc. The only thing he hasn't done is taken off the garage door and put in a proper window. At the moment the only light comes from a 2 ft square non opening window at the opposite end to the garage door, so it is a bit like a cave.
We are thinking of adding a loo and sink under the stairs, taking off the garage door, bricking up and adding a proper opening window. Any ideas how much that will cost? Where will the water come from for the loo etc? Does that have to come down from the existing bathroom or will there be pipework outside we can tap into?
The heating is in the form of an electric storage heater which is adequate as it is only going to be an occasional guest bedroom.