The system's unit: the price breakdown
A unit price breakdown (precio descompuesto) adds up, for one unit of work: materials with their waste coefficients, labour (output in hours per unit multiplied by the hourly cost of each grade), machinery, auxiliary means (often via reusable auxiliary prices, such as a mortar) and the site indirect cost percentage. The structure serves to audit a received price, to adapt it to the project and to build prices that exist in no database.
Of its components, the most sensitive is the output: small variations in hours per unit move the price more than material prices do, and it is the least verified component. The complete construction is developed in unit price breakdowns: how they are built, with a step-by-step example as application.
The references: price databases
Price databases (regional reference databases and widely used professional ones) publish standard breakdowns, updated periodically, with associated measurement rules. Their good use follows three rules: choose the database consistent with the area and works type, declare it as the project's reference (codes and rules), and systematically adapt outputs and material prices to real conditions; a database is a calibrated starting point, not an automatic budget. The overview and selection criteria are in price databases: which exist and how to use them, with the BC3 format (FIEBDC) as the exchange standard between tools.
Prices in motion: new rates
When the works require an unforeseen unit, the price is agreed as a new rate (precio contradictorio), built with the same breakdown structure and, as far as possible, with the components already present in the contract (same hourly costs, same indirects, analogous materials). That continuity is the best defence against arbitrary negotiation: the new price is deduced from the existing price system instead of being invented under schedule pressure. Regime and method in new rates.
| Price component | Content | Where it is checked |
|---|---|---|
| Materials | Quantities per unit of work, with their wastage | Current price database and supplier quotation |
| Labour | Output in hours per unit and hourly cost | Provincial agreement and comparison with similar works |
| Auxiliaries | Intermediate prices used by several items | The single definition of the auxiliary in the system |
| Indirect costs | Declared percentage on direct costs | Budget report and tender documents |
The four analyses in this branch
Unit price breakdowns. The complete structure, component by component, and its audit uses.
Price databases. The Spanish landscape, selection criteria and adaptation rules.
Labour outputs and auxiliary prices. The breakdown's sensitive component and the system's reusable pieces.
New rates. When they apply, how they are built and how they are negotiated.
The essentials
The Spanish pricing system works as a coherent construction set: auditable breakdowns, declared reference databases, adapted outputs and new prices deduced from the same rules. The discipline that keeps it useful is twofold: always adapt the references to the specific project, and preserve the breakdown's traceability throughout the works, because it is the rulebook for changes. Its application to monitoring (certifying, controlling, valuing change orders) is developed in the economic monitoring branch.
Note: usual conventions and practices in Spain in 2026; each contract's regime prevails.