Buildings which are listed or which lie within a conservation area are protected by law. This does not mean that you can never alter or demolish one, but carrying out relevant work without the appropriate consent is a criminal offence. Unfortunately many building contractors and even some architects who do not specialise in historic building work are unaware of the alterations which require consent, leaving them and their clients liable to criminal prosecution.

In brief the following works require consent throughout England, Scotland, Wales and Northern Ireland:

• All works affecting a scheduled monument or the ground surrounding it require scheduled monument consent.
• The demolition or alteration of a listed building and historic structures within its grounds requires listed building consent.
• The demolition of an unlisted building in a conservation area requires conservation area consent.
• Alterations to the exterior of all buildings may also require planning permission and an application may be needed for some works to houses in conservation areas and other buildings affected by an 'Article 4 direction' which otherwise would not require one.

Although there are slight variations in the legislation protecting historic building and conservation areas throughout the UK, the same principles apply.

Conservation Area Consent

The demolition of a building requires conservation area consent if the building is situated within a conservation area. (Prior to the case of Shimuzu v Westminster City Council in 1997 'demolition' was taken to include the demolition of part of a building, such as a chimney stack or a front porch. However, on appeal the House of Lords ruled that the removal of part of a building constituted an alteration, not demolition. As a result the demolition of a part of a building in a conservation area no longer requires conservation area consent, no matter how important that part is to the character of the building and of the conservation area).

Unauthorised demolition is a criminal offence.

Listed Building Consent

No person shall execute or cause to be executed any works for the demolition of a listed building unless the works are authorised.

Listed building consent is required for all alterations to listed buildings and their interiors irrespective of their grade or category of listing. It is also required for alterations to any object or structure which lies within the grounds or 'curtilage' of a listed building and which was constructed before 1 July 1948.

This may be taken to include garden walls, sundials, dovecotes and other such objects and structures as well as buildings which are ancillary to the principal building, not separated from it, and were so at the time of listing. It is important to note that altering a listed building without consent is a criminal offence.