City Evolution - digital
In order to take a more rigorous and scientific approach to the building stock we first need to look at the way buildings are counted. The more accurately we can count buildings and classify them, according to their characteristics and use, the easier it will be to identify, analyse and predict relationships and patterns of behaviour within the stock as a whole. This will also give us back a common language, essential in enabling effective dialogue to proceed.
Buildings, as we have said, are the building blocks of our cities. However at present the UK appears to hold no published counts of the number of buildings in cities or in the country as a whole. Furthermore, information on building form and use is only made available by government in aggregated form, preventing precise quantities of specific building morphologies from being easily assessed.
Buildings today are in fact rarely used as units of measurement. As in other European countries, different ways of measuring stock have been developed by different sectors and bodies. Output Areas are the smallest geographic unit for which census data, for example, is published. These are designed to provide a small, stable geography for local statistics which also, in averaging around 125 households, enable data privacy
be maintained. Housing, property tax and land ownership data on the other hand are stored by ‘property’ (if relating to an individual address), by ‘dwelling’ (if relating to a self-contained domestic physical structure), by ‘household’ (if relating to a dwelling’s occupants), and by hereditament/floor space, which can span across buildings (if relating to a commercial or industrial building). Listed buildings are recorded as whole structures, however multiple buildings can be recorded as a single list ‘entry’, with counts also including structures such as railings and telephone boxes. The exact number of designated buildings is unknown.
During the 19th and early 20th century buildings were a more common unit of menasurement. Census information, which began in 1801, describe' houses' and 'buildings'. Larger blocks are seen as distinct units, within which there are sub demarcations for households where there was divided occupancy. Rates at this time tended to be charged on whole houses, not on dwellings or households.
In the London County Council 1940s assessment of WW11 bomb damage for example, every bombed building in London was given a colour code. From this the precise amount of buildings with a specific level of damage could be quickly quantified, and the location of prority areas for intervention identified. But from the late19th century the number of purpose built flats grew, with large scale estates built after WW1 and developed on a much larger scale after WW11. These included high rise blocks known as 'streets in the sky' where the population of an entire street was contained within a single building with a single entrance. Structural subdivision of older properties and inclusion of multiple addresses within a single building also became common.
Building footprints, able to contain one or many properties and/or households, provide a unit of measurement understood by everyone. To this land parcel, 'dwelling', 'household' or 'property' data can all be related . Metadata release using building footprints in many other countries is now giving us national (the Netherlands has 9,866,539) and citywide building counts. Though the latter may be of more relevance for comparison between UK cities owing to comparable morphologies, international comparisons (for different building age groups, uses, and square meterage) are also of relevance to energy assessment.
At the moment even using OS MasterMap, the UK most advanced (restricted) digital mapping product, an automated count of UK building footprints is not possible. This is because liftshafts (shown below in red within tower blocks), balconies, external staircases etc particularly within postwar buildings are counted as separate polygons.
As explained in our open footprint section, the UK urgently requires comprehensive simplified building outlines from OS to facilitate smarter approaches to city sustainability. These include enabling currently fragmented data/counts to be locked into, and related to, building footprints ie recognisable and understandable spatial locations, for which metadata is able to be visualised.
Further discussion of issues relating to building counts will be posted here such as those relating to commercial premises spanning across more than one footprint, and questions concerning building subdivisions within large-scale social housing blocks.