Q. Is there a limit to the size of an extension I can build at the back of my house?

HMH: Yes. 40 square metres (about 430 sq.ft) but there are certain limitations you also need to be aware of. Any earlier (post 1963 extension) is taken out of this area. The area is an internal wall measurement but if a section of back wall becomes “internal” it’s area also needs to be included. The extension must be single storey except for 12 square metres which can be upstairs in a terraced or semi-detached house or 20 sq.m. for a detached house. This upstairs extension also need to be at least 2 metres from the site boundary. There are other restrictions on upper storey windows. Remember that if your house is a protected structure the above rules may not be assumed as the “character” of the house needs to be considered carefully.