Variations in construction projects occur due to inadequate, incomplete, inconsistent contract documents, drawings, and project specifications or due to errors or missed out parts in them. Project documents with such occurrences often give rise to claims or disputes resulting in change orders from the contractor. Carefully and comprehensively prepared, and thoroughly reviewed contract documents would minimize the potential of such incidents, and the designers, architects, project managers should take appropriate measures to ensure that the contractors are issued error-free, adequate, consistent and complete sets of contract documents prior to agreement signing.

Another area for initiation of variations is errors and uncomplete tender documents. It is the responsibility of contract managers, quantity surveyors, or construction managers to review tender documents for detecting such incidents and rectify it during tender evaluation and negotiation period.

A frequent source of variations is the inconsistency of contract documents. For large projects, the contract documents include large volumes with thousands of pages and it may be extremely difficult to maintain consistency in the documents considering that different volumes are prepared by different departments of the owner or the architects or consultants. One way to avoid variations due to such causes is to establish the precedence of documents in the Conditions of Contract.