Small buildings become exempt from needing an EPC on the basis of their size if they are completely detached and have a floor area of less than 50m2.
Other small buildings below 50m2 are not exempt.
These are the requirements of the Department of Communities and Local Government. The RICS Code for Measuring Practice is used to assess the net internal floor area.
This is the case for EPCs required at the point of sale or let. However, all buildings, irrespective of size will require an EPC for a feed-in tariff assessment or for the Green Deal.
