The first conservation areas were created in 1967, and there are now over 8000 conservation areas in England. Local authorities have the power to designate as conservation areas in any area of 'special architectural or historic interest' whose character or appearance is worth protecting or enhancing. This 'specialness' is judged against local and regional criteria, rather than national importance as is the case with listing. English Heritage can designate conservation areas in London, where we have to consult the relevant London Borough Council and obtain the consent of the Secretary of State for National Heritage. The Secretary of State can also designate in exceptional circumstances - usually where the area is of more than local interest.
Procedures are basically the same as for listed building consent applications.
Generally there is a presumption in favour of retaining buildings which make a positive contribution to the character or appearance of the conservation area. If you live in a conservation area, you have to obtain permission before making changes which would normally be permitted elsewhere, to ensure that any alterations do not detract from the area's appearance. These changes include certain types of cladding, inserting dormer windows, and putting up satellite dishes which are visible from the street. Under legislation introduced in 1995, local authorities can make further restrictions on the kind of alterations allowed, depending on how these might affect the key elements of buildings in the conservation area. Examples might be putting up porches, painting a house a different colour, or changing distinctive doors, windows or other architectural details.