Changes to the scope of a project beyond the final authorization inevitably result in longer duration and higher costs. Freezing of scope allows detailed design and material procurement to progress rapidly without rework and inefficiencies; and results in better budget accuracy with lower overall costs. Conceptual design and project definition should have progressed to the point that the authorization (definitive) cost estimate can be developed.
Evaluation of alternatives, value engineering, constructability input, and safety reviews should be completed before the scope is frozen. An effective change control process must also be in place. Team factors include a high level of trust among the owner, contractor, and other team personnel; inclusion of a user representative; and commitment to avoid scope growth, even if funds are available. Subdivision of the project into smaller components produces quicker and more concise definitions, resulting in shorter durations. Resistance to changes after a scope freeze must be driven by the owner Management. Costs for implementation of process changes that support early freeze should be weighed, but are usually relatively small. (RS41-1, p. 4)