ABSTRACT
The national heritage of the built environment in its widest sense is very considerable; as indicated earlier it probably represents something of the order of fifty times the annual net additions (Chapter 5). It contains development of all ages, exceptionally going back to the building of the Romans. Clearly its continued existence depends on continuous maintenance and adaptation to meet current needs. While each year some of the built environment ceases to be useful because of physical, functional and financial obsolescence, most of it has a long potential life. There are many demands for change as population and human activities migrate from one place to another and change in scale, and as changes occur in technology, lifestyles and human preferences. Given the sheer scale of existing built environment and the limited resources available to extend, replace, adapt and maintain it, there is a need to make the best use of what is available.
