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The paper describes the development and application of physical-financialmodelling techniques to the analysis of relations between development design –covering the broad characteristics of a scheme, such as land use mix, developmentdensity and built form – and financial viability. It is divided into two parts

severely restricting the reliability and accuracy of any assessments of financial viability or marketability. As the project proceeds better information becomes available but this is at the price of increased ‘lock-in’. The developer knows more about the scheme but has less scope to react to that knowledge by withdrawing from or altering it without incurring substantial costs.

For the developer, the key design-related part of the development process is the transition from principles and possibilities to the position where the main physical parameters (development density, site morphology and use) are fixed. That is, the move from project inception, where "a few simple sketches [are compared with] ‘back of an envelope’ calculations" (Syms, 2006, page 6, square brackets added), to the detailed scheme design and feasibility study. The latter stage will include drawings of sufficient detail to obtain planning permission and a full financial appraisal, incorporating sensitivity and cash flow analyses. However, it is not clear how one progresses from the one position to the other. Most texts refer to a process of constant review so that "each time the design is refined, viability is reassessed" (Adams, 1994, page 50). Computer packages are used: by developers to assess the financial implications of change (Byrne, 1996; Syms, 2002; Havard, 2008); and by architects to develop designs and to discuss changes with the client (Tunstall, 2006). However, there is no significant integration of financial appraisal and CAD software.

All the development texts reviewed by Crosby et al (2008) take a single, fixed design as the starting point of the development appraisal. Sensitivity analysis - the assessment of the impact of specified changes upon project viability - considers market variables (such as rents, yields, prices, interest rates and building costs) but not design change. This is reflected in the structure of development appraisal software. Havard (2008) illustrates the application of industry-leading software to development appraisal. Complex, sophisticated financial analyses are supported. However, the user must enter all the physical and financial details of each part of the subject scheme (Ibid., pages 238-239). These include the use, gross floor space, net/gross ratio, construction costs and rents/yields or selling prices for each building type. Consequently, if the design is changed, most of these input variables - especially those relating to floor space, use and number of floors - have to be altered manually. While this may offer a time-consuming and awkward link between design and finance, no such link is made within CAD software. Tunstall (2006) lists 14 advantages of CAD but none relate to using it to explore the relation between design form and financial structure.

Techniques that provide a more effective link between design and finance therefore address an important shortcoming in the current set of analytical tools available to developers, designers and others with an interest in promoting schemes with higher design quality. It is to the development of such techniques that we now turn.

Visualization and Financial Appraisal

Visualization Techniques

The physical form of the built and natural environment has long been represented in visualizations. Before the digital era traditional analogue techniques such as plans,