We first clarify which area is being calculated
Building footprint, gross floor area, usable area and saleable or lettable area answer different questions. The rules for measuring and accounting for each must be specified. Revenue must be calculated on the quantity that can actually be sold or let, and costs on the corresponding technical scope. A net-to-gross ratio can be used for an early estimate if it is labelled as an assumption. As surveys and layout assessments progress, it must be replaced by an itemised area schedule.
We test the brief against a workable layout
The number of homes that can be accommodated depends on the structural layout, building depth, daylight, circulation, escape routes and the space needed for building services. Apartment proportions, ease of furnishing and the relationships between rooms affect everyday use and, in turn, market appeal. We therefore check the area-based target against at least one layout option developed by a designer. We also establish the space required for shared and service areas, and feed the specialist findings back into the area schedule and cost estimate.
Parking can change the financial case
In the P-01 illustrative example, the calculated residential and commercial scheme requires more parking spaces than can physically fit on the site. Resolving the shortfall requires evidence of the chosen solution's legality, actual capacity and the durability of the right to use it, as well as its implementation cost and timescale. We treat these as conditions of the development scheme and financial model. If the required parking cannot be secured, a smaller scheme or a different use must be assessed and recalculated.
Identify the evidence required
The assessment is based on the survey, documents describing title and use, applicable regulations and available drawings. We check the documents’ dates, their consistency with one another and their relationship to the actual condition. Depending on the assignment, these are supplemented by structural and other specialist investigations, utility providers’ capacity information, layout options and market comparisons. For every material input, we state whether it is a verified fact, a specialist estimate or a working assumption that still requires checking.
The development brief provides a basis for decisions and design
A substantiated development brief specifies the intended use, required quality, space requirements and key conditions for implementation. It makes clear which quantities are already supported by assessments and which depend on further decisions or verification. We also identify the changes that would require the financial appraisal to be revised. For open questions, we specify the investigation, responsible party and decision point. This enables the investor to judge which uncertainties warrant the next investment of time and money.
The examples are illustrative and do not describe client projects.
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