There are over 370,000 listed buildings in the UK, all with their own special charm. Period features and eccentricities can be a real draw, but what exactly does listing mean for a potential owner? Is that beautiful old cottage you have your eye on just a crumbling wreck of paperwork and frustration?

'Listing' is essentially the legal protection of important buildings against demolition, alteration or extension. While overall responsibility for listing lies with the Secretary of State, it's the job of English Heritage to assess and advise on applications. Of course it's not just residential properties that are listed; pubs, warehouses, factories and theatres can all warrant careful preservation. Criteria for listing include:

Age

The older and rarer a building, the better it's chances of being listed. Buildings constructed before 1700 which have survived in their original condition are pretty much guaranteed to make the list. Anything dating before 1840 stands a good chance too. From 1840 onwards there are more surviving examples so requirements are stricter. A building will need some special interest above and beyond its age. While modern buildings can be listed, those built after 1945 will need something exceptional about them to be listed.

Listed Property Owners Club

Architectural Interest

The style and proportions of a building are important factors. Properties built by notable architects will get bonus points, as will those featuring important examples of building techniques or layout. Any alterations must be judged to have added or preserved architectural interest rather than detracting from it.

Historical Interest

Connections with historic figures or events can work in a building's favour. A passing lodger won't count for much, but many buildings have played significant roles in Britain's social, economic, cultural or military history.

Group Value

Some buildings which wouldn't necessarily make the grade on their individual merit will be listed because of their 'group value' This tends to be when a building forms part of an important architectural unity or example of planning, such as a square, terrace or model village.

Listed buildings are graded to reflect their relative importance:

• Grade I are those of exceptional interest
• Grade II* are particularly important and of more than special interest
• Grade II are of special interest and warranting preservation. Around 92% of listed buildings fall into this category.

When thinking about buying a listed property it is important to check that any changes made by previous owners have been carried out in accordance with the strict regulations governing renovation and maintenance. Listed properties are protected inside and out, and you can't change the character of the building without permission in the form of Listed Building Consent (LBC). Alterations requiring applications include:

Listed Property Owners Club

• Painting over brickwork
• Removing external surfaces
• Adding dormer windows or roof lights
• Changing roofing material
• Putting up aerials or satellite dishes
• Removing internal walls
• Altering fireplaces, panelling or staircases

As a new owner, you can't be prosecuted for someone else's shoddy work or failure to acquire LBC. However, you do need to watch out in case you are forced to rectify previous mistakes from your own pocket. This can be a real nightmare, and it is well worth bringing in a solicitor or surveyor with experience dealing with listed buildings. You can also get useful information from the Listed Property Owners Club www.listedpropertyownersclub.co.uk and English Heritage www.english-heritage.org.uk.