Variation Order in Construction: How Changes Are Priced

No building is constructed exactly as first drawn. Owners change their minds, ground conditions surprise, authorities add requirements and design coordination exposes clashes. A variation order is the formal instruction, issued under the contract, that changes the work the contractor must do. How variations are instructed, valued and recorded is one of the main reasons projects either hold their budget or drift far beyond it.

This article explains what counts as a variation, who has authority to order one, how variations are typically valued, how they affect time, and how both owners and contractors can manage them well. It describes common principles across standard forms; the precise mechanism always depends on the wording of your contract, and nothing here is legal advice.

What counts as a variation

Most standard forms define variations broadly. A variation generally includes:

Additions or omissions of work, such as an extra storey of balconies or the deletion of a feature wall.
Changes in quality, kind or specification, for example a change of floor finish or a higher concrete grade.
Changes in levels, lines, positions or dimensions.
Changes to the sequence, timing or method of work where the contract specified them.
Changes to site conditions imposed by the employer, such as restricted access or working hours.

Not every change is a variation. Work the contractor was already obliged to do, such as correcting its own defective work or completing items that were reasonably inferable from the contract documents, does not entitle it to extra payment. The boundary between “extra work” and “work already included” is where many disputes begin, which is why a clear scope at tender is so valuable.

Who can issue a variation order

Under most standard forms, only the contract administrator can instruct a variation: the architect under the SIA Building Contract, the Superintending Officer under PSSCOC, or the employer’s representative under many design and build forms. Instructions from anyone else, including the owner speaking directly to the site foreman, may not bind the contract and may leave the contractor unable to recover payment.

Instructions should be in writing. Many forms contain a procedure for confirming oral instructions: the contractor confirms in writing within a short period, and if the contract administrator does not contradict that confirmation within a further period, it takes effect as a written instruction. Under the 2020 edition of PSSCOC for construction works, for example, both periods are three working days. Whatever the form, the safe course is to put every change in writing before the work is done.

A contract administrator’s power to order variations is not unlimited. Changes that alter the fundamental nature or scale of the work may fall outside what the contract contemplates. This is a legal question that turns on the facts and the wording, and should be referred to legal advisers if it arises.

How a variation order is valued

Standard forms generally follow a hierarchy of valuation rules, usually applied by the quantity surveyor or contract administrator:

Contract rates apply directly where the varied work is of similar character and carried out under similar conditions to work priced in the contract.
Contract rates form the basis where the work is similar but the conditions or quantities differ significantly; the rates are adjusted pro rata.
A fair valuation is made where there are no applicable rates, typically built up from reasonable costs of labour, materials and plant plus overheads and profit.
Daywork may be used where work cannot properly be measured, paid on recorded hours and materials at agreed rates.

Omissions are normally valued at the contract rates for the work omitted. Most forms do not permit the employer to omit work simply to give it to another contractor, and doing so can expose the employer to a claim for the contractor’s lost profit.

Increasingly, contracts ask the contractor to submit a quotation before the variation is instructed, so that cost and time effects are agreed in advance. This is good practice wherever the change is not urgent, because a variation priced after the event is harder to challenge and more likely to be disputed.

Time effects and indirect costs

Variations rarely affect only the direct cost of the work. Additional work on the critical path delays completion, and most forms allow an extension of time for instructed variations, protecting the contractor from liquidated damages. Where the contract permits, the contractor may also recover prolonged preliminaries or loss and expense caused by the disruption.

Demonstrating that effect usually requires a credible programme. A schedule built with the critical path method allows the parties to show whether a variation actually delayed completion or simply consumed float. Without that analysis, time claims tend to become arguments of assertion.

Managing variations well

Variations are not inherently bad; they are how a contract adapts to reality. Problems arise when they are frequent, late or poorly documented. Several habits reduce the risk:

Complete the design before tender as far as is practicable. Many variations are design development in disguise.
Freeze decisions on finishes and layouts at agreed milestones, and recognise that late changes cost more than early ones.
Price before instructing, except for genuine emergencies.
Keep a variation register recording each instruction, its status, agreed value and time effect.
Check knock-on effects: a change to an opening, a load or a services route may need structural review, permit amendments or resubmission to authorities.

Structural changes deserve particular care. Relocating a column, adding a water tank or enlarging a slab opening may look minor on an architectural drawing but can require redesign, fresh calculations and, in Singapore, amended plans endorsed by a Professional Engineer. Value-driven changes are best handled through structured value engineering, so that savings are tested against performance before they are instructed.

When variations accumulate unchecked, they become one of the principal causes of cost overruns. Our consultancy regularly reviews the structural implications of proposed changes before they are priced.

Frequently asked questions

Can a contractor refuse a variation order?

Generally a contractor must carry out variations validly instructed under the contract, but it may be entitled to object to changes outside the contract’s scope or those the contract allows it to decline, so the wording should be checked.

Is an email a valid variation instruction?

It may be, if the contract’s notice provisions allow electronic communication and it comes from the person with authority to instruct variations. Contracts differ, so check the notice clause and confirm formally where in doubt.

Who values a variation?

Usually the contract administrator or quantity surveyor values it under the contract’s valuation rules, often starting from the contractor’s quotation or claim, with disputes resolved through the contract’s dispute process.

Do variations automatically extend the completion date?

No. An extension is normally granted only if the variation actually delays completion, and the contractor usually has to give notice and supporting evidence within the time the contract requires.

Is this legal advice?

No. It is a general explanation; the effect of any variation depends on your specific contract and facts, which should be reviewed by a qualified adviser.

Need a structural review of a proposed change before it is priced or instructed? Talk to our consultancy or get in touch.