Urban morphogenesis at the microscale: how houses change

The incidence of change to existing houses and gardens within England's interwar residential areas is examined, the focus being on sample areas originally developed by private enterprise in Birmingham and London. Larger-scale changes, mostly subject to development control by the local authority, notably the building of additional houses within existing gardens, subdivisions and amalgamations of houses, changes of use, extensions and other significant structural works, are distinguished from changes initiated by households without planning permission, and often without building permission, such as changes to chimneys, reroofing, and changes to doors, windows, porches, and gardens. Changes subject to development control are negatively correlated, and smaller-scale changes are positively correlated, with the dwelling density at which the sample areas were originally developed. Among the factors responsible for this are the greater susceptibility of the areas of higher dwelling density to the contagious diffusion of minor and cosmetic changes.