Concept, basic and execution design in a luxury renovation: what each delivers

What is the difference between concept, basic and execution design?

A concept design (anteproyecto) shows the idea: layout, style, volumes and a budget reference. A basic project (proyecto básico) sets the general characteristics of the building and is enough to apply for a licence, but not to start work. An execution project (proyecto de ejecución) describes everything down to details and specifications, and it is what you build from and fix a price on.

The three levels run in sequence, and each is tied tightly to the one before. The Spanish Technical Building Code (CTE) states directly that the execution project develops the basic one and cannot reduce the performance declared in it. That protects you: an attractive picture in the first phase will not turn into a simplified version in the second. In practice the same designer normally produces all three levels, because reworking someone else's documentation costs more than completing your own.

What does a concept design include and why do you need it?

A concept design answers the question of what is being built, and it is cheap compared with the cost of a mistake on site. It exists so that you make the main decisions before anyone starts calculating money.

In practice it includes two or three layout options, 3D visuals of the main rooms, a material direction (stone, wood, metal, colour), a lighting scheme and a budget reference as a range. It is a tool for conversation, not the basis of a contract. A concept design is not submitted to the town hall and cannot fix a price: it has no pipe sections, no tile or slab layouts, no socket schemes.

The most common mistake is to treat a concept as a project and ask for a fixed price. The contractor will either refuse, or name a figure with a large margin, or accept the price and later bill every clarification as extra work. It is better to read the concept as a range and move on.

What does a basic project contain?

A basic project describes what the building is and what its characteristics are, without execution detail. Under the CTE (Anejo I), it includes a report, general drawings and an approximate budget by chapter.

The report covers the parties involved (promoter, designer, other technicians), background information, a description of the solution, the declared performance of the building, ground and foundations, and fire safety. The drawings: location plan, site plan, general floor plans, roofs, elevations and sections. The budget is approximate, by chapter.

For a licence application on works that need one, a basic project is normally enough. The CTE puts it this way: its content is sufficient to request the licence but insufficient to start construction. Which exact package the town hall will accept for your works is confirmed with the technician and with the town hall itself, because it depends on the type of work. For a quote, a basic project gives a reference, not a price.

What drawings does an execution project for a renovation include?

An execution project contains everything needed to build without guesswork: report, drawings, technical conditions, quantities and a detailed budget. It is the document from which the contractor measures quantities and the installer knows what goes where.

Under the CTE, the execution project consists of a report (descriptive and constructive, with justification of CTE compliance and annexes: structural calculation, services, energy efficiency, quality control, health and safety study), all necessary drawings including structure, services and construction details, a specification (pliego de condiciones) with requirements for materials and for the execution of each work unit, quantities (mediciones) and a detailed budget with a price schedule. A control plan is a separate part.

In a luxury interior renovation, this set is usually extended with sheets that a construction project does not carry: tile and stone slab layouts, wall elevations, lighting, switch and socket schemes, ceilings with concealed recesses, drawings of fitted furniture and joinery, a sanitaryware specification, climate system schemes. These are the sheets that turn an expensive finish into something that can be ordered and built right the first time.

Do you need an execution project for a fixed-price quote?

In practice, yes. A firm price needs quantities and a specification, and those come from the execution project. Without it you are left with a quote built on assumptions and provisional sums for whatever is undefined.

That does not mean drawing every last screw. Part of the items can go in as a sum for unchosen materials, and how to do that without surprises is covered in another article. But the less documentation there is, the more lines in the quote rest on assumptions, and the wider the possible gap between the quote and the final payment. There is also an article on this site on how a fixed quote differs from measured pricing.

A practical rule: if you want a fixed price for a good renovation, give the contractor measurements, execution drawings and a materials specification. If there is no project yet, ask for an honest range with the list of assumptions.

Who signs the project, and which package does the licence need?

A technical project is signed by a designer whose qualification matches the type of works: an architect, an engineer or a technical architect, depending on the intervention. The Spanish Building Act (LOE, Ley 38/1999) treats the designer as a separate party, and the works are supervised by the works director and the execution director.

The roles under the LOE are these. The designer (art. 10) drafts the project in line with technical and planning rules. The works director (art. 12) answers for the technical side and signs the start record and the final certificate. The execution director (art. 13) controls execution and the quality of materials and signs the interim certifications. The contractor builds to the project and the contract. Who may sign a project for your works is explained in the article on signing technical projects, and the list of documents for the town hall is in the article on licence documentation.

An interior design project is usually drawn up and signed by an independent specialist (a designer or architect). BCN YARD works from such projects and runs the quote and the build, while the signatures on projects belong to independent specialists.

How does the project connect to the quote and the schedule, and how does BCN YARD work with it?

The usual order is: concept, survey and measurements, basic project (if a licence is needed), execution project, detailed quote, contract. Skipping the execution project does not save time; it moves the time to the site, where every undrawn decision is made under pressure.

The execution project lengthens preparation and reduces changes on site. Stone, concealed doors, bespoke furniture and climate systems are ordered only from drawings: in the 250 m² children's psychology centre in the Eixample there were 24 concealed doors and ventilation with heat recovery, and items like these are not ordered by feel.

At BCN YARD the exact price appears in the quote after the survey and measurements. We run projects in Russian and Spanish, answer an enquiry within an hour, one person is responsible for the project, and payment follows the contract, in stages. If you have a concept or a project from a designer, send it over: we will calculate quantities from the drawings and show which sheets still need to be drawn to make the price firm.