Worked example: a unit price breakdown step by step

📐 Focus⏱ 6 min read

The best way to fix the breakdown's structure is to build a complete one. Chosen unit: m² of single plasterboard partition on metal framing, with insulation, in new construction under average conditions. The values are pedagogical and rounded: they illustrate the method, they do not replace a current price database.

Step 1: materials, with their waste

Material Quantity per m² Waste Unit price Amount
Plasterboard 15 mm (2 faces) 2.00 m² 5 % €4.50/m² €9.45
Metal framing (studs and tracks) 3.20 lm 5 % €1.60/lm €5.38
Mineral wool 48 mm 1.00 m² 5 % €3.00/m² €3.15
Screws, compounds and joint tape Set n/a n/a €1.80
Materials subtotal €19.78

Step 2: labour

Grade Output Hourly cost Amount
Installer (first grade) 0.35 h/m² €24.00/h €8.40
Assistant 0.18 h/m² €20.00/h €3.60
Labour subtotal €12.00

The output is the price's strong hypothesis: 0.35 h/m² assumes normal series on a clear site. In fragmented renovation, the same partition can go to 0.45-0.50 h/m², and the price rises by several euros without any material changing.

Step 3: auxiliaries, indirects and total

Item Calculation Amount
Auxiliary means (2 % on directs) 0.02 × 31.78 €0.64
Indirect costs (3 %, the project's convention) 0.03 × 32.42 €0.97
Unit price (PEM level) €33.39/m²

Level reminder: this price lives at PEM. Overheads and industrial profit (13+6 convention) are applied on the whole budget to form the contract budget, as detailed in PEM and PEC.

What the example teaches

Three readings. The hierarchy of sensitivities: the output (€12 of 33) is the dominant lever; materials are market-verifiable; auxiliaries and indirects are declared conventions. The role of waste: the systematic 5 % adds almost a euro per m² here, invisible item by item and very visible in the mass. And the audit use: faced with an offer for this partition at €28 or €42, the breakdown locates the divergence in minutes (optimistic output, overvalued material, loaded indirects) and turns haggling into a technical conversation.

Note: rounded pedagogical values for Spain in 2026; real prices are taken from a current database adapted to the project.

Frequently asked questions

Materials with their wastage, labour with its output and hourly cost, then auxiliaries and indirect costs as declared percentages. The partition example runs through all three steps.

€12 out of a unit price of €33.39/m², making it the dominant lever. A worse output moves the result more than any material does.

A systematic 5 per cent adds almost one euro per m² here. It is invisible item by item and very visible in the budget total.

No. They are illustrative and rounded: they show the method and are replaced by those of a current price database adapted to the project.

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