The concept of 'time at large' is based upon the 'prevention principle' and arises when the contractor is delayed in completion due to some act of the employer, which 'prevents' timely completion. In order to avoid the prevention principle from applying many construction contracts and sub-contracts include provisions for extension of time. 'Time at large' is a concept often raised by contractors who have, for one reason or another, found it difficult to obtain an extension of time to complete their work on a project. Additionally, the development of alternative methods of extension of time determination may prevent time being set 'at large'. The contractor needs to ensure that its claims for extensions of time are both correct in terms of what is claimed but also timely. This leads to the issue of 'time-barred claims'. It considered was whether a contractor's claim for loss and expense was time-barred as it was not made within 28 days of the adjudicator's decision.