Construction, demolition and adaptation are core dynamic processes operating concurrently and continuously in cities at a range of rates and scales; from rapid comprehensive development and demolition across multiple blocks, to minor removals and additions to small-scale plots over time.

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Each process generates a constantly changing amount of form and space available for different activities. The ability of urban stocks to evolve sustainability, and efficiently, relies on a number of factors including:  quality of build, adaptability of construction structural systems, the capacity to extend incrementally in; system repairability (and affordability of these repairs) , conditions of ownership and planning policy frameworks.

The move towards a circular economy also relies on demolition and renewal being precisely targeted and for buildings to be reused wherever possible.

The rate of turnover, or churn in the stock, and the lifespan of buildings, and the number, type and location of buildings built anew, adapted and demolished, has significant implications for cities both in their capacity to create conditions to flourish in socio-cultural and economic terms, and their ability to reduce energy and material flows to meet global greenhouse gas targets. Reducing demolition rates and increasing reuse for example  keeps building materials, and their associated carbon reserves, held within stocks which turn this reduces emissions, waste related extraction, and processing associated with replacement. Throwing away finite, complex and expensive resources,  that have evolved, adapted and been tested over many decades, or in some case centuried , without proper assessment, is also of increasing concern.

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Colouring London's 'Dynamics' (Lifespan/History) category has been set up to allow demolitions and lifespans of London's buildings to be spatially tracked  for the first time. This is done by capturing  pairs of dates, and main land use for all historical constructions and demolitions on sites, since the first development on fields/previously unbuilt-on land. These date entries are essential to improving accuracy in urban metabolism/ long-term stock forecasting models. This is because mature stocks such as London's are relatively slow moving systems, with a c1% turnover per year. As such accurate future forecasts of spatial patterns of change, and long-term  cumulative impact of loss of buildings and the shortening/lengthening of lifespans require spatio-temporal data spanning extensive periods - i.e. over 150 years. These data are also necessary to generate visual simulations and evolution animations.

This, as in the case of our Age Category,  is designed  to be of specific interest to building historians, and those interested in building history. It is also designed to to demonstrate the the critical contribution of the humanities  to the sustainable planning agenda.

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