The older a building is, the more chance there is that it’s listed. As a general rule, listing applies to all buildings built before 1700 and to most built between 1700 and 1840. The vast majority of listed buildings are Grade II listed, but more important ones are Grade II* and the most important are Grade I. In Scotland, categories A, B and C are used instead of grades. The listing applies to the whole exterior and interior of the building, and sometimes attached structures and buildings as well.
Listed buildings are considered to be of special historical or architectural interest of national importance. Listing doesn’t mean that the building can’t be altered or extended - it often can, but the local council will have more control over what changes are made to it and may refuse permission for alterations if it doesn’t think they’re appropriate. Listed building consent is required to make alterations and while some home improvements, such as internal redecoration, can usually be done without consent, many others, such as removing original features, knocking down walls and building extensions, can’t.
Listed building consent is obtained from your local council and is a similar process to applying for planning permission, although in some cases you’ll need planning as well. Historic England (see www.historicengland.org.uk for information on listed buildings), or Historic Scotland in Scotland (www.historic-scotland.gov.uk), may be consulted by the council about whether the alterations would be appropriate, especially with more important listed buildings.
Before making any changes to a listed building, you should consult your local council’s conservation officer, as work that seems minor may require consent. The officer should be able to advise you about what sort of work will be considered appropriate for the building (and what won’t) and any consents required. Altering, demolishing or extending a listed building without consent is a criminal offence and can result in a prison sentence and large fine, as well as other costs, so it’s not something you want to risk.
If listed building consent is granted, you may have to use traditional building materials and techniques to comply with it. These are often more expensive and specialised than standard ones - traditional lime plaster instead of conventional modern plaster, for example - as replacements are usually on a like-for-like basis.