The complete structure
| Component | Content | Sensitivity |
|---|---|---|
| Materials | Supply price delivered to site, with a waste coefficient per material (cuts, breakage, losses) | Medium: prices verifiable in the market |
| Labour | Output (hours per unit, per trade grade) × the grade's hourly cost | High: the output is the decisive component |
| Machinery | Equipment hours × hourly cost (depreciation or hire, consumption, operator where applicable) | Medium |
| Auxiliary means | A percentage or reusable auxiliary prices (mortars, pastes, small materials) | Low per unit, relevant in mass |
| Indirect costs | A percentage on direct costs distributing site expenses not attributable to items | The project's declared convention |
The sum's total is the unit price at PEM level. Overheads and industrial profit do not live inside the breakdown: they are applied afterwards on the whole, as detailed in PEM and PEC.
The two components that decide the price
The output. It is labour's multiplier and the component with the most real variance: the same partition consumes different hours on a clear site or in occupied renovation, in a long series or around openings. Price databases publish average outputs under average conditions; adapting them to the project's real conditions is the professional gesture that separates a calibrated budget from a copied one. The detail is developed in labour outputs and auxiliary prices.
The waste coefficient. Every material carries its own (large formats lose more to cutting, fragile materials more to handling), and forgetting it produces systematically short prices that the site corrects the painful way.
The breakdown's three uses
Auditing. Faced with a received price, the breakdown allows the divergence to be located: not "this price is expensive" but "this output doubles the database's" or "this material is valued above market". The conversation changes nature.
Adapting. The same breakdown is recalibrated for the project: outputs according to execution conditions, materials according to real local prices, indirects according to the specific site.
Building. For units that exist in no database, the structure gives the method: compose materials, estimate the output by analogy with known units, apply the same auxiliaries and indirects. It is also the construction rule for new rates on site.
The essentials
A breakdown is five components with a clear hierarchy: the output decides, waste corrects, materials and machinery are market-verifiable, auxiliaries and indirects are declared as conventions. Its three uses (auditing, adapting, building) make the format the cost consultant's daily working tool and the rulebook for site changes. The complete application to a real case is in the step-by-step example.
Note: usual conventions in Spain in 2026; the specific percentages and coefficients are those each project declares.