Built-up areas (BUAs) and built-up area sub-divisions (BUASDs) are a new geography, created as part of the 2011 Census outputs.
This data provides information on the villages, towns and cities where people live, and allows comparisons between people living in built-up areas and those living elsewhere. Census data for these areas (previously called urban areas) has been produced every 10 years since 1981.
A new methodology to capture the areas was used in the 2011 version, but it still follows the rules used in previous versions so that results will be broadly comparable. As before, the definition follows a ‘bricks and mortar’ approach, with built-up areas defined as land with a minimum area of 20 hectares (200,000 m2), while settlements within 200 metres of each other are linked.
The built-up areas and built-up area sub-divisions are available as boundary sets, name and codes and lookup files, which can be downloaded from ONS's Open Geography portal.
Users will need to be aware that there are areas included in the boundary datasets but not in the Census tables. These built-up areas and built-up area sub-divisions have been identified as areas that have not been allocated a population. In most cases this is because they do not have any residential buildings – for example, industrial estates, airports, theme parks, etc. There are 337 BUAs where population has not been allocated (305 in England, 32 in Wales) and 133 BUASDs where population has not been allocated (123 in England, 10 in Wales). The names and codes of these areas have been included in documentation that accompanies the files.