How much will it cost?
The Royal Institute of Chartered Surveyors (RICS) gives a guide cost of between £1,260 and £1,680 per square metre for an extension with plastered finish. So they estimate that the shell of a 20-square metre, single-storey extension might range from £25,200 to £33,600 – that’s for base, walls to plaster finish, tiled roof, one radiator, …