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Contracts & Legal

Modification

In Plain English

Any official written change to the contract after it has been signed.

Definition

A modification is any change to the contract documents after they are executed, including change orders, construction change directives, and written orders for minor changes. All modifications must be in writing to be enforceable. Modifications adjust the contract sum and/or contract time and become part of the contract documents.

Why It Matters in Bidding

Estimators must price modifications precisely because each one resets the contract sum and schedule, and unpriced or poorly documented changes are a leading source of disputes and lost margin. During bidding, understanding how a contract defines and authorizes modifications tells you how much risk you carry when scope shifts after award. Tight modification language protects both cash flow and the right to recover added costs.

Example

When the owner adds a rooftop unit after award, the GC issues a change order modification adding $42,000 and 10 days to the contract before the subcontractor begins fabrication.

Related Terms

Change OrderChange DirectiveAddendumContract Sum

Frequently Asked Questions

A change order is one type of modification. The broader category also includes construction change directives and written orders for minor changes. All three are modifications because they formally alter the executed contract, but they differ in who signs, how pricing is agreed, and whether work can proceed before the price is settled.
No. Standard contracts require modifications to be in writing to be enforceable, protecting both parties. Verbal directions to change scope create payment disputes because there is no agreed price, time impact, or signature. Estimators and field staff should refuse to proceed on cost-bearing changes until written authorization exists.
Not always. A written order for a minor change can adjust the work without affecting the contract sum or time. Other modifications adjust price, schedule, or both. The estimator's job is to evaluate each one and document any cost or time impact before the modification is executed.

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