The detailed methodology of the process used across the UK by ONS in 2011 is set out in 2011 Built-up Areas - Methodology and Guidance, published in June 2013. It is summarised as "..a ‘bricks and mortar’ approach, with areas defined as built-up land with a minimum area of 20 hectares (0.2 km2 / 0.077 mile2), while settlements within 200 metres of each other are linked. Built-up area sub-divisions are also identified to provide greater detail in the data, especially in the larger conurbations."[1][2]
The total population of the built-up area defined on this basis in 2011 was 65,692 at the 2011 census[3] making Wrexham the fourth largest built-up area in Wales, and largest in North Wales at the time. This accounts for almost half (48%) of the entire country borough's population of 136,055 residents,[4] with the remainder living in Rhosllanerchrugog's built-up area of 25,362 residents (2011 census)[5] or in various villages and towns in rural parts of the county borough.
2021 census
For the 2021 census, the "Wrexham built-up area" was reduced to 44,785 residents, with other areas formerly considered part of the BUA split into separate ones.[6]
Subdivisions (2011 census)
The ONS provides sub-division statistics for the Wrexham built-up area for the 2011 census.