Previously there were three rooms in one space in that house: bathroom, leading to a toilet and a tiny little kitchen. None of these rooms were functional - all very tiny, dark and quite outdated. There was already a separate bathroom upstairs installed. So, the owners decided they didn't need another bathroom downstairs. And, like in many Edwardian houses, there was a side passage leading to the back garden, which could be utilized better.
We removed all the old appliances, finishes and equipment from site, knocked down the solid built partitions, broke the concrete floor and excavated it to the level suitable for floor insulation. Then we concreted foundations, built a new party wall and rear wall, joining into the original rear wall. It was good that neighbours gave a consent for a party wall - the wall could be built on a boundary line. This means saving around 15cm of internal space - in London every little centimetre counts. Once finished with the construction of the shell, we insulated the floor, concrete screeded the floor, drylined walls and carried out all the usual finishing jobs.
This type of extension is quite expensive in terms of costs per square metre - although the extra space built is not large, it costs same as to build a decent size rear extension. There is a great benefit though - the internal space of such properties can be arranged in a much better way and the actual floor space then increases quite considerably.
Below - images of what this property looked like before us and how we progressed.