The canonical hierarchy
| Level | Content | Golden rule |
|---|---|---|
| Economic levels | PEM (direct works budget), contract budget, total cost | Every figure declares its level |
| Chapters | Major work blocks in construction order | Stable, comparable structure across projects |
| Sub-chapters | Breakdowns where the chapter requires them | Only if they aid reading, not by habit |
| Work items | The elementary unit: code, description, unit, quantity, price | The description is contractual |
The economic levels are the trade's first source of misunderstanding: the exact definition of PEM and PEC, their conventional percentages and the documents where each appears are developed in PEM and PEC: definition and differences. The typical order and content of the chapters, with their usual weights by works typology, are covered in the budget by chapters.
The work item: the system's cell
The whole system rests on the quality of the work items. A complete item contains: a unique code (its own or inherited from the reference price database), a description defining the element, its materials, its installation and its inclusions, a unit of measure consistent with the measurement rule, the quantity and the unit price.
Three drafting rules concentrate dispute prevention. What is not described does not exist: builder's assistance, trims, testing and certifications are described or lost. The unit follows the rule: measuring a partition in m² deducting openings above a certain threshold requires saying so in the item, because the tendered unit price depends on it. One item, one element: omnibus items grouping heterogeneous work prevent precise certification and partial valuation when the scope changes.
Lump sums: the controlled exception
Lump-sum items (partidas alzadas) assign a global amount without quantities. They are legitimate for what genuinely cannot be measured at design stage and dangerous when they replace definition: every lump sum is a space of interpretation that will be negotiated on site. Their two regimes (to be justified, integral payment), correct uses and risks are developed in lump-sum items: types, correct use and risks.
The three analyses in this branch
PEM and PEC: definition, differences and uses. The budget's economic levels, their conventional percentages and the map of documents where each appears.
The budget by chapters. The typical structure of a building project, each chapter's content and usual weights.
Lump-sum items. The two regimes, legitimate uses and the drafting rules that limit risk.
The essentials
The budget's structure is a convention serving three uses: designing, contracting and monitoring. Declared economic levels, chapters in stable construction order, work items with complete contractual descriptions and lump sums reduced to what strictly cannot be measured: with those four disciplines, the budget serves all three uses at once. Its natural counterpart, the method that fills the quantities, is developed in the takeoff branch.
Note: usual conventions and practices in Spain in 2026; each contract's regime prevails.