When it applies and when it does not
It applies when the executed unit does not exist in the contract's price schedule and cannot reasonably be assimilated to an existing one. It does not apply when the unit exists with a different quantity (that is a quantity variation, handled by the contract's prices) nor when the difference lies in foreseeable execution conditions the offer should have incorporated. The boundary matters: every unnecessary new rate opens a negotiation the agreed prices had already closed.
The construction: deduce, do not invent
The new rate is built with the breakdown's structure and, as far as possible, with the components already present in the contract:
| Component | Priority source |
|---|---|
| New materials | Prices justified with supply quotations |
| Labour | The contract's same hourly costs |
| Outputs | By analogy with comparable units in the contract's own schedule |
| Auxiliaries and indirects | The contract's same percentages and auxiliaries |
| Overheads and profit | The contract's, applied as in the other prices |
That continuity has a double virtue: it confines the negotiation to the genuinely new components (usually materials and output) and produces prices consistent with the contract's general level, defensible before any later review. Starting each new rate from scratch instead opens the whole price to discussion.
The negotiation and the file
Three disciplines separate the technical new rate from the contentious one. Before execution: the price is proposed, discussed and approved before execution whenever urgency allows; a price negotiated with the unit already executed is negotiated without an alternative. In writing: a broken-down proposal, approval by the client or its site direction, and formal incorporation into the contract's price schedule. With traceability: each new rate is numbered, linked to its cause (change order, discovery, design indefinition) and feeds the record the final account will consolidate.
In public works, the new-rate regime is governed by the applicable procurement rules, with their own procedures and limits specified in the tender documents; the price construction logic is the same. The tender documents are worth reading before proposing the price, since they set the procedure and the periods.
The essentials
The healthy new rate is recognisable by three traits: it applies only to genuinely new units, it is deduced from the contract's price system instead of being invented, and it travels in writing before execution. Its volume is also a management indicator: many new rates signal design indefinition or badly used lump sums upstream, and their aggregate treatment belongs to change orders.
Note: usual practices in Spain in 2026; in public works, the applicable procedure is that of the procurement rules and the tender documents.