Permitted development is an aspect of town and country planning in the United Kingdom which allows people to undertake minor development under a deemed grant of planning permission, therefore removing the need to submit a planning application. Permitted development is currently set out in the Town, Country and City Planning (General Permitted Development) Order 1995 (amended in 2008).
Extensions at ground level are now principally governed by maximum dimensions depending upon the location and number of storeys e.g. a single storey extension to the rear of a detached house should be a maximum of 4 metres deep from the original rear wall and a maximum of 4 metres high. There are additional clauses relating to using similar materials, side windows to upper floors, eaves heights etc
Small porches (up to 3m² externally) follow the previous guidance including a maximum height of 3m and minimum distance from a highway of 2m.