The documentary content
The design content annex of part I of the CTE (Código Técnico de la Edificación, the Spanish building code) organises the proyecto de ejecución in four blocks. All four are delivered together and none is dispensable.
The report, with its descriptive part inherited from the básico and its construction part fully developed: foundations, structural system, envelope, compartmentation, finishes, conditioning and services, together with CTE compliance justified basic document by basic document and compliance with the rest of the applicable regulations. This regulatory justification, with its sheets and verifications, is the part of the design that speaks directly to municipal control and to later quality control.
The drawings, now of complete definition: structure with its details, services developed and sized, construction sections, joinery, and a level of detail sufficient for the works to be executed without interpreting. A drawing that forces interpretation on site generates new rates.
The specifications, particular technical and administrative conditions, which set how the work units must be executed and accepted. They decide any dispute over the acceptance of a unit.
And the economic block: the mediciones (bill of quantities) and the budget, with unit prices and breakdowns, which turns the drawn building into an accountable building. From that structure come the contract, the certificates and the settlement.
To this core are added the concurrent studies and documents required by their own regulations, with the health and safety study as the universal piece. Each follows its own regulation and its own validation where applicable.
The quantities: the economic heart of the document
For the construction economist, the bill of quantities is the piece that distinguishes a serious detailed design from a decorative one. Measuring is describing the works in contractable units: each item with its complete definition, its explicit measurement rule and its quantity justified on the drawings. From that description flow, in chain, the design budget, the clean comparison of tenders, the unit-price contract, the monthly certification of executed works and the final settlement.
The quality of a set of quantities is recognised in four traits: completeness, without forgotten units that later surface as new rates; explicit measurement rules consistent with the price databases used; traceability, every quantity reconstructible from the drawings; and structure, ordered chapters that allow comparing and certifying without archaeology. The methodological detail of this craft is developed in the guide to mediciones y presupuestos (Spanish bills of quantities and budgets) and, for the specific document, in the article on the bill of quantities of the detailed design.
The document everything is measured against
The reference status of the proyecto de ejecución has practical translations in every later phase. In procurement, it is the common base on which contractors tender: identical quantities for all make offers comparable, and its errors become contract disputes. On site, it is the control benchmark: the execution direction verifies what is built against its drawings and specifications, and certifies against its quantities and prices. At closure, it is the settlement yardstick: what was executed is settled by comparison with what was designed and contracted.
This centrality explains the formal control the rules reserve for it: the proyecto de ejecución of building works is one of the documents subject to obligatory professional validation under Royal Decree 1000/2010, and its regulatory justification is what is checked in the licence procedure, as developed in the article on justifying the CTE in the design within the guide dedicated to the code. Validation and licence check different documents of the same design.
Coherence with the básico and change management
The detailed design must develop the licensed básico without betraying it: the parameters the licence controlled, areas, heights, coverage, use, are untouchable without a licence modification, while technical development is its natural territory. Professional management of this boundary involves documenting changes between versions: a básico-ejecución differences table, with its classification, admissible development or alteration subject to modification, saves discussions with the municipality and leaves a trail for financiers and purchasers.
Economic reading: what documentary gaps cost
| Typical gap | Deferred cost |
|---|---|
| Unmeasured units | New rates on site, negotiated without competition |
| Ambiguous measurement rules | Certification disputes month after month |
| Missing construction details | Interpretation on site, uneven quality, late orders |
| Generic specifications | Unit acceptances without an enforceable standard |
| Incomplete regulatory justification | Licence requirements, delays |
The investment rule is clear and counterintuitive for the hurried developer: the proyecto de ejecución is the best place in the process to spend one more week. Every hour of measurement and detail avoids multiples of its cost on site, where the same problems are resolved with the works stopped, the contractor in a position of strength and the calendar against you.
Frequent errors
The first is inheriting quantities from previous projects and adapting them superficially: inherited rules and quantities are the classic source of ghost items and omissions. Quantities are taken from the actual design rather than from a precedent.
The second is closing the budget before the drawings, with quantities that no longer correspond to the final delivered document. The correct order is final drawings, then quantities and budget.
The third is treating the specifications as filler literature: in a unit acceptance dispute, the specifications are exactly the only thing that counts. The specifications are written for the project's actual units.
The fourth is neglecting the chapter and item structure thinking only of the design: that structure will be the contract's, the certifications' and the settlement's, and its defects are dragged to the end. Adopting a standard structure before measuring starts is worth the effort.
Note: the required content of the proyecto de ejecución is that of the design content annex of part I of the CTE, completed by the sectoral and regional regulations applicable to each works.