A revision constitutes a change or variation to an initially presented—or in-progress—design concept, and is typically a change of less than 1/4 of the design. A revision is simply meant to be a slight modification or course correction to progress toward the final design. A new design concept is not considered a revision. This means that a new design concept would be an addition to the project, and would need to be estimated separately, in addition to the current project estimate.