The preliminary studies: verify before drawing
The preliminary studies are the information phase: gathering and verifying everything that conditions the project before investing in designing it. Their characteristic content is organised on four fronts.
The planning front: what the urban plan allows on the site, buildable area, uses, heights, coverage, setbacks, and what charges or constraints weigh on it, from heritage protections to easements. It is the sovereign check, because an error here invalidates everything after.
The physical front: the survey of the site or the existing building, the geotechnical study when the stage allows it or at least its provision, the available urban services and the pre-existing conditions. Without that survey any design assumption is left without a base.
The brief front: what the developer needs, in areas, uses and performance, and with what priorities when the site cannot take everything. The priorities are written down before drawing and signed off.
And the economic front: the first cost envelope, built from market ratios on the brief's areas, with a wide and honest range. At this point of the process, a context reference such as the guide to construction cost per square metre in Spain is exactly the kind of data the estimate needs.
The deliverable of the phase is not a design: it is an informed decision. Proceed, adjust the brief, renegotiate the land or abandon, with numbers and constraints on the table.
The anteproyecto: the solution before the commitment
With the information verified, the anteproyecto (preliminary design) translates the brief into an overall architectural solution: siting, massing, floor organisation, first areas by use, general image. Its level of definition is deliberately open, without construction detail or complete regulatory justification, because its function is to compare and decide, not to process.
What is decisive about the anteproyecto is the list of variables it freezes. Shape and compactness, which govern the envelope area per useful square metre and with it a substantial part of the facade cost and the future energy bill. The position of the cores, which determines circulation, evacuation and common area. The structural grid, which fixes spans and with them the system and cost of the structure. The ratio between built and useful area, which is the measure of the design's economic efficiency. None of these variables will ever again be so cheap to change: at basic design, touching them costs redesign; at detailed design, it costs a project; on site, it costs serious money.
Estimating without quantities: the craft of the envelope
The classic objection to early estimating, there is nothing to measure, confuses measurement with estimation. In preliminary studies and anteproyecto one estimates by ratios: areas by use multiplied by market unit costs, corrected by the factors the prior information has already revealed, intended quality, site difficulty, probable structural system, local price context. The correct result is not a figure but a range with written assumptions, which narrows at each following stage.
Two practices separate the professional estimate from the conversational number. First: declaring the perimeter, what it includes and what it does not, works, fees, taxes, external works, VAT, because half of the economic misunderstandings of projects are born from different perimeters in different heads. Second: versioning the estimate with the design, so every evolution of the scheme has its economic echo and deviations are detected on paper rather than in the contractors' tenders.
Economic reading of the two stages
| Decision of the stage | Economic lever it fixes |
|---|---|
| Brief and areas | The size of the whole problem |
| Choice and negotiation of the land | The land cost per sellable square metre |
| Shape and compactness | Envelope cost and energy demand |
| Grid and structural system | The structure chapter and its schedule |
| Target quality level | The positioning of the entire budget |
The economic synthesis is the funnel rule stated in the process guide: the capacity to influence cost is maximal here and only falls afterwards. The best-invested economist hours of the whole process are those of these two stages, when every alternative can still be compared for the price of a calculation.
Frequent errors
The first is starting to draw before verifying the urban plan, designing on a buildable area or a use the site does not admit. The planning check comes before the first sketch.
The second is skipping the anteproyecto out of haste and entering the basic design directly, losing the only cheap iteration of the overall solution. That iteration costs days and avoids redesigns measured in weeks.
The third is estimating with a single ratio and no assumptions, generating an unreal economic anchor that will chase the project all the way to the tenders. A ratio is always accompanied by its scope and its date.
The fourth is not versioning: a brief that grows, qualities that rise and an estimate that is never touched, until the rude awakening with the detailed design's quantities. Every change of brief requires the estimate to be revised.
Note: the contents described correspond to usual professional practice; the naming and scope of the preliminary stages can vary with the commission and the type of developer.