Change orders: economic valuation

📐 Article⏱ 7 min read

The change order (modificado) is the scope change with a name of its own: the contracted design and the one to be executed no longer coincide. Its economic management is simple in theory (value the change under the contract's rules) and demanding in practice, because it competes with schedule urgency and the temptation to "sort it out at the end".

The typology and its valuation

Type of change Valuation
Quantity variation of existing units Contract prices applied to the new quantities
New units New rates built with the contract's structure
Deletion of units Deduction at contract prices, with attention to costs already incurred (stockpiles, preparatory work)
The change's indirect effects Schedule, site resources, replanning: valued explicitly or waived explicitly, never left in silence

The fourth line is what separates well-closed change orders from postponed conflicts: a change that lengthens the works has a time cost (site resources, supervision staff, time-related overheads) that exists even if nobody writes it down. Silence does not eliminate it: it transfers it to the final account.

The documentary discipline

The change order managed in real time is a technical operation; the one rebuilt after the fact is a dispute. The healthy sequence: a written change order describing the scope, economic (and schedule) valuation before execution whenever urgency allows, approval by someone who can commit the developer, and formal incorporation into the contract (updated price schedule and current budget). Every piece numbered and traced: the change-order register is one of the files the final account will consolidate.

When urgency forces execution before valuation, the order is preserved in its essentials: a written instruction to proceed with valuation reserved, joint measurement of what is executed before it is concealed, and immediate valuation afterwards. What can never be rebuilt is the prior physical state.

Public and private

In the private market, the change order is a contractual matter: a well-drafted contract provides the procedure (who instructs, how it is valued, what happens to the schedule) and the parties follow it. In public works, contract modification is governed by the applicable procurement rules, with enabling cases, quantitative limits and formal procedures specified in the tender documents: the room for agreement is smaller and documentary rigour even more decisive.

The essentials

The change order is governed with four gestures: typify the change, value it under the contract's rules (new rates included), treat its schedule effects explicitly and document it before execution whenever possible. Its aggregate volume is also a project management indicator, read alongside deviation control.

Note: usual practices in Spain in 2026; in public works, the modification regime is that of the procurement rules and the tender documents.

Frequently asked questions

A change in the contracted scope, valued against the contract prices. It differs from a new rate, which creates a price for a unit not foreseen.

With contractual prices where the unit exists, and with new rates where it does not. The valuation is documented before execution, not after.

An instruction from the site direction, an accepted valuation and a record of the agreement before execution. Executing first and documenting later turns a variation into a dispute.

No. In public works variations are governed by procurement rules, with their own limits and procedures set out in the tender documents.

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