The question of what sort of residential mix is most ësustainableí is much debated by UK policy makers. It would seem obvious that an appropriate mix of new housing provision would cater for the diverse needs and incomes of households. However, there is strong evidence within the UK that housing developers have been reluctant to provide for this and rather have had a tendency to focus upon the construction of either high density apartments or large detached houses (Bramley & Brown 2008). The question arises as to whether the UK planning system should more actively promote a broader mix of housing developments? If so, it will need a stronger evidence base and diagnostic tools. Hence, the aims of this research are to analyse the implication of residential mix (type and density) upon house prices and use this output to simulate viability of alternative residential development schemes. The research will be undertaken in two stages. First, to develop hedonic house price models suitable for analysing values associated with different mix and density across England. This analysis will provide the capability to predict the likely sale prices for different hypothetical mixes of development in different locations. Second, utilise these hedonic prices, to provide a modelling capability to estimate development costs and residual land values across England, for defined new product mixes. By combining the hedonic price predictions and development costs it is then possible to provide an analysis of development viabilities (residual values) for a range of possible scheme mixes and densities. This would be a valuable addition to the information base for local planning authorities by indicating which residential mixes are most likely to be preferred by developers and which would be unlikely to proceed.