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Acceleration in Building and Construction Contracts

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Timing is a vital part of any building and construction contract and understanding the implications of delays can help in avoiding disputes.  The same can be said for when an employer wants a project completed ahead of time, known as acceleration. Andrew Cullyer, Litigation Executive specialising in construction disputes, examines the process and consequences of acceleration, discussing the very real dangers of getting the basics wrong in a project and explaining how disputes can be avoided. 

Time and acceleration in construction contracts

Time in building and construction contracts can be for a fixed period or a reasonable time.  When discussing acceleration of time, we are usually referring to projects that have a fixed period for completion. On such a project, an employer may wish for the project to be finished earlier than currently set out in the contract. The contractor may agree to this earlier date and be able to provide additional labour and material to achieve the new time scale.

Where a contract is not for a fixed period it is not clear how this principle would apply. However, if additional labour and materials are provided, then a reasonable time would likely and objectively be judged to be shorter than if those additional materials and labour were not provided. 

Any acceleration can usually only be instructed by agreement between the parties or by strict adherence to contractual procedures for acceleration. It is important that any agreement is clearly defined or that any contractual procedures are strictly followed.

Cost of acceleration in construction contracts

There is no obligation on the contractor to carry out this additional work for free. Indeed there is usually a substantial additional cost to accelerate the works.

It is important that either the totality of these costs are agreed upfront or, at least, the method of calculation is clear, and unambiguous. A failure to do this will increase the likelihood of disputes.

Delay and acceleration

When there are multiple different events affecting the likely completion of a project, some of which are delays and some of which are accelerations, things can get very complex, very quickly.

The delay of works that do not trigger effective acceleration does not necessarily mean there is no right to additional payment.

Where there is an agreement to accelerate the works to achieve an earlier completion date but those works are delayed such that the works are not completed any earlier (and no acceleration is achieved) then it becomes a complex question of whether the additional costs of any attempted acceleration are payable. This will usually be determined by who was responsible for any delay.

Where the works are delayed or in delay and an acceleration is agreed, then the possible outcomes include:

  1. The works are completed earlier than they otherwise would be;
  2. Or they are not and there has been no effective acceleration.

In either situation there is often a dispute over additional payment.  Usually, delay must be mitigated by the contractor irrespective of all else or where there has been no tangible benefit of acceleration.  Such arguments are multifaceted and it is impossible to say what the correct advice is without close analysis of the facts and circumstances.

There is not always a simple and straightforward answer. The more complex the construction project and the more complex the party agreement(s), invariably the more time consuming and costly it will be to sort out should a dispute arise.

You will save the most amount of money and time in the long run if you:

To have your questions answered on your construction project or if you wish to bring a claim against a party involved in your construction project, you can contact Andrew Cullyer today on 023 8071 7482 or email

For general Litigation or Dispute Resolution enquiries, contact Amelia Ford on 023 8071 7429 or email


This is for information purposes only and is no substitute for, and should not be interpreted as, legal advice.  All content was correct at the time of publishing and we cannot be held responsible for any changes that may invalidate this article.