Dealing with variations in building contracts

Variations to the scope of works, or variations to the services to be provided, under a construction project are common in the building industry.

A variation may be requested by either party or arise out of necessity, for example, due to changes required in legislation or because of a latent condition.

When negotiating a variation, it is important to follow the process required under the contract and to ensure that the variation is clearly documented.

What is a variation?

The scope of works to be provided under a building contract will generally be set out in attached specifications, plans, or a service brief, which together form the whole contract.

The scope of works is an integral part of the contract. It identifies those works for which the contractor will ultimately be liable and is the basis from which alterations or additions will be classified a variation. The categorisation of a variation is important as it affects a contractor’s right to claim additional costs and a principal’s obligation to pay them.

The following concepts are relevant in determining what constitutes a variation:

  • The variation must be requested and be something that is not already covered in the scope of works. If there is no request by a principal to vary the scope of works, a contractor will have difficulties in claiming additional costs.
  • Similarly, if higher quality materials are provided than what is specified in the scope of works, a contractor will not have a right to charge for the upgrade unless this was specifically requested.
  • Work that is indispensably necessary to complete the job, although not spelt out in the contract or scope of works, is not a variation. An example of work that is intrinsic to the job is the installation of hinges when hanging doors – although the specifications may not refer to ‘hinges’ per se, it is obvious that the provision and installation of doors cannot be completed without this component.
  • A complete change to the scope of works by the principal is not a variation and may give a contractor a right to terminate the contract.

Dealing with variations

Variations to the scope of works often lead to disputes in the construction industry. It is therefore important that both parties understand the significance of a variation and the processes required for requesting and claiming them.

A principal may require that the contractor undertake more or less work than that provided in the scope of works. Issues can arise where a contractor is not qualified for, or does not have sufficient resources to, undertake the additional work. Similarly, if work falling within the scope of works of a contract with one contractor is given to another contractor, this will be problematic for both parties and may result in a breach of the contract by the principal.

To avoid a potential breach which could allow a contractor to terminate the agreement, principals should ensure that their contracts contain provisions that enable them to request variations to the original scope of works. The contract should identify the circumstances under which a variation might be requested and set out clear processes for varying the scope of works or services.

Principals should also be aware of the difference between a variation and a complete overhaul of the scope of works which may entitle the contractor to terminate the contract.

Contractors should ensure that they will be adequately paid for works additional to the original scope and follow the processes outlined in the contract for applying for modifications.

A variation may be requested by a contractor who needs to carry out additional work to fulfil the scope of works. This may occur where latent conditions arise. Latent conditions are physical conditions on the development site that are materially different to those that would reasonably have been contemplated, notwithstanding a contractor having made all due inspections and investigations of the site.

The contract will generally provide a timeframe during which a contractor may notify the principal of a pending variation. The contractor will typically be required to set out reasons why the variation is required and the costs in carrying out the additional work. The contractor should always obtain approval before undertaking any variations.

Quantum meruit claims

In some circumstances, strict compliance with the variation procedures set out in the contract will not be commercially efficient. The need to make a variation may arise without adequate time to follow due process, particularly when it is necessary to avoid delays or wastage.

Even if they are refused payment for the variation on the basis that the correct process was not followed, a contractor may still have a quantum meruit claim. In this case, the amount of the claim will be a reasonable price for the work carried out by the contractor, often based on industry standards.

A principal that requests and supervises a variation, despite the fact that the formal process was not followed, will be prevented from benefiting from the additional or modified works.

To succeed in a claim, it must be shown that the principal received a benefit, the contractor incurred expenses in doing the work, and that it would be unfair for the principal to retain the benefit without paying for it.

A contractor who refuses to undertake work requested by a principal that falls well outside of the scope of works provided in the contract, may also have a quantum meruit claim. One example of this is work that is unexpected and that does not ordinarily fall within the principal’s area of construction. In this case, if the contract is terminated, the contractor may be paid for the work completed to date.


A clearly defined scope of works and detailed process for dealing with variations must be included in all construction projects.

The scope of works should be sufficiently detailed and cover additional matters that may arise during construction of the project. The clearer the scope of works, the easier it will be for both parties to recognise and deal with a variation.

If you or someone you know wants more information or needs help or advice, please contact us on +612 9248 3450 or email