"Construction projects rarely run as expected. Additional works may be required by the client as the project progresses, or may become necessary because of unforeseen conditions on site. Unanticipated delays will mean a project will take longer to complete, or the cost may rise unexpectedly. All of these events could give rise to a claim - the assertion of a right, usually by the contractor, to an extension of the contract period or an additional payment under the terms of the building contract. While the basis of a claim may be real, many claims advanced by contractors are unsound, often because the basic principles are misunderstood"--