Teoría y práctica del diseño urbano para la reflexión de la ciudad contemporánea

242 Teoría y Práctica del Diseño Urbano ness, but more fundamentally to certain characteristics of the residential development process. Market conditions Housing quantity has been one of the ‘overriding preoccupation(s) of planning for much the last 100 years’ (Carmona et al., 2003). Inmore recent times we have witnessed what has been called the ‘affordability-led’ housing supply de- bate (Gallent and Tewdwr-Jones, 2007) where the main issue for housing policy makers has been to plug the gap between the long-term increase in house prices and its consequent lack of affordability for increasing numbers of households. House building is a risky and uncertain business, partly due to the time lag between the start of the development process and the sale of the completed house. The housing market is also volatile and particularly susceptible to ‘shocks’ that affect the demand side of the market, such as interest rate move- ments or credit availability, as graphically illustrated by the credit crunch of 2007/08. Additional sources of uncertainty derive from planning reg- ulation: whether land will receive planning permission, and under what terms, including the content of section 106 plan- ning agreements (which are designed to deliver particular lo- cal or community benefits as part of planning permissions). Paradoxically, planning is meant to increase certainty for de- velopers, but delays in the preparation of plans and the discre- tionary nature of planning control, mean that planning is of- ten a source of uncertainty in addition to market volatility. In this context house builders have traditionally been attached to a restricted range of standard house types, which are ‘tried, tested and sell’ (Hooper and Nicol, 1999). Build costs are pre- dictable, design costs are minimized and allegedly conserva- tive mortgage providers and new home buyers are not put off. As such the debates about design quality stemming from is- sues of housing quantity are interesting. In the affordability- led housing market it is interesting that a number of com- mentators indicate that market pressures lead to ‘product homogenisation’ (Carmona et al ., 2003; Gallent and Tewdwr- Jones, 2007; Punter, 2007; amongst others). In other words the type of development produced by the housing market is a re- sult of the restrictive planning system that appears to favour