The provision of “affordable” homes is an issue of profound international importance. It is estimated that 1.6 billion people live in substandard housing and that 100 million people are homeless. The problem is particularly acute in relation to the growing urban sector where every week more than a million people are born in, or move to cities in the global South. Approximately 1 billion people (32% of the global urban population), live in urban slums. If no meaningful action is taken, the United Nations reports that the number of slum dwellers worldwide will increase over the next 30 years to nearly 2 billion.