Last Updated: 29 October 2026
Quick Summary
A variation is a formal, written change to the scope of work under a building contract, while change orders is the American term for the same thing. Both require a written instruction, a cost adjustment and usually a time extension, and the contract wording determines which clause applies.
- Under NEC4, the contractor commonly submits a compensation event quotation within three weeks unless the contract is amended.
- A variation agreed verbally and never written down is the most common cause of a budget overrun at final account stage.
- Number every variation sequentially and never reuse a number, as a missing reference is the first thing a quantity surveyor will query.
- Liquidated damages do not apply to delay caused by the employer's own variations.
- Agree the variation procedure, valuation method and notice period in writing before the first skip arrives.
Table of Contents
- Variations vs Change Orders: What the Terms Actually Mean
- Why Variations Are Unavoidable in Older Properties
- How a Construction Contract Variation Template Protects Both Sides
- The Impact of Change Orders on Project Timeline
- Approval Workflows, Signatures and Keeping Records
- How to Dispute a Builder's Extra Costs
- What to Agree Before Your Builder Starts on Site
- Frequently Asked Questions
Variations vs Change Orders: What the Terms Actually Mean
That distinction matters more than most homeowners realise. The disputes that arise on residential projects rarely start with bad intentions. They start with a builder saying "change order" while the contract says "variation", and neither side agreeing on what that triggers.
Both describe the same event: work that differs from the agreed scope. Both require a written instruction, a cost adjustment, and usually a time extension. The difference is procedural, and procedure is what protects your money.
Why the Wording Matters on a Renovation Contract
Your construction contract defines how a formal modification is administered. Under JCT contracts, variations are governed by a specific clause that sets out how the contractor must be instructed and how the cost is valued.
Use the wrong term and you may find yourself arguing about which clause applies. A verbal agreement to "add a change order" carries no weight if your contract only recognises written instructions issued as variations.
Why Variations Are Unavoidable in Older Properties
Open a wall in a Victorian terrace and you will find something the survey could not see. Rotten lintels, outdated wiring, a chimney breast removed without proper support.
So when a homeowner asks us how we can promise a timeline on a loft conversion when nobody can predict what is behind the walls, the honest answer is that we cannot predict it.
A common mistake is treating every discovery as a dispute. Most are simply omissions and additions that need documenting, valuing and signing off before work continues.
How a Construction Contract Variation Template Protects Both Sides
A construction contract variation template is a standard form that records the change, its cost, its effect on the project programme, and both parties' signatures.
The template does not need to be complicated. It needs to be consistent.
Most guides stop at that description. The useful version is the form itself, so here is a model variation request you can adapt to your own contract.
Model Variation Request Form
Project details
- Project address and contract reference
- Contract form and edition (for example, JCT Intermediate Building Contract 2016, or NEC4 Engineering and Construction Short Contract)
- Date of instruction and variation reference number
The change
- Description of the work being added, omitted or altered
- Reason for the change and who requested it (employer, contract administrator, or site discovery)
- Drawing or specification reference affected
Cost
- Priced adjustment, broken down by labour, materials, plant and preliminaries
- Basis of valuation (schedule of rates, dayworks, or fair valuation under the contract)
- VAT treatment
Time
- Effect on the programme, stated in working days
- Proposed extension of time, if any
- Revised completion date
Authority
- Contract clause under which the instruction is issued
- Name and signature of the person authorised to instruct the change
- Employer's acceptance and date
Record
- Date work is to start
- Cross-reference to any early warning or compensation event notice already issued
What a Variation Request Should Always Include
- A clear description of the work being added, omitted or altered
- The reason for the change and who requested it
- A priced cost adjustment, broken down by labour and materials
Watch out: a variation agreed verbally and never written down is the single most common cause of a budget overrun at final account stage. If it is not on paper, it did not happen.
Where the Standard Forms Differ
Under a JCT contract, the variation is instructed by the contract administrator and valued under the valuation rules in the contract conditions, which typically allow a schedule of rates, dayworks, or a fair valuation where neither applies. Under an NEC4 contract, the equivalent mechanism is the compensation event: the project manager instructs a change, the contractor submits a quotation within the period stated in the contract (commonly three weeks unless amended), and the quotation is assessed against the defined cost plus fee.
The Impact of Change Orders on Project Timeline
Every variation carries a time consequence, even the small ones. Ordering a different tile or moving a socket means the trades behind that decision wait, and the delay ripples through the programme.
This is where the impact of change orders on project timeline becomes financial. Building contracts often include provisions for liquidated damages if the contractor runs late, and these usually account for agreed extensions.
The mechanism that resolves this is the extension of time, and it is worth understanding before you sign anything. How to ensure builders stick to timelines sets out practical ways to hold the builder to the agreed programme once variations start pushing dates.
Extension of Time, Not Just Delay
An extension of time is the contractual adjustment to the completion date that follows a variation or a relevant event. Under a JCT contract, the contract administrator must assess the delay and notify an extension within the period set by the conditions; the contractor is usually required to give notice of the delay as soon as it becomes apparent. Under NEC4, the equivalent sits inside the compensation event process: the contractor's quotation must state the effect on the programme and the completion date, and the project manager accepts or assesses it.
The Notice Trap
Most disputes about time are not about the facts; they are about notice. A common pattern is a contractor who carries out extra work on a verbal instruction, then discovers at final account that no extension was ever recorded and the completion date has passed. The employer argues the delay is the contractor's; the contractor argues the variation caused it.
Sequencing and Batching Decisions
Where a variation is unavoidable mid-stage, ask the contractor to state which trades are affected and whether the delay is on the critical path. A two-day delay to a tiling decision may cost nothing if the plasterer is still working; the same delay to a structural steel decision can push the whole programme. Recording that distinction in the variation document is what turns a vague argument about time into an evidenced claim.
Approval Workflows, Signatures and Keeping Records
Whatever system you use, the workflow should be the same:
- The change is identified on site and logged
- The contractor prices it and issues a written variation
- The homeowner reviews the cost and time impact
- Both parties sign and date the document
- The variation is filed against the project baseline
- The final account reconciles every variation issued
If you want to see how a builder formally runs this through a live project, read how we work from first site visit to final sign off.
Every variation should follow the same six-step workflow, from logging the change on site to reconciling it in the final account.
| Step | What to do |
|---|---|
| 1 | Change identified on site and logged |
| 2 | Contractor prices it and issues a written variation |
| 3 | Homeowner reviews the cost and time impact |
| 4 | Both parties sign and date the document |
| 5 | Variation filed against the project baseline |
| 6 | Final account reconciles every variation issued |
How to Dispute a Builder's Extra Costs
Start by checking whether the cost was genuinely additional. Ask for the variation document, the original scope of work, and the clause in your contract that permits the charge.
Genuine disputes usually fall into three categories: work claimed as additional that was already in scope, variations issued without prior written instruction, and costs that have been marked up beyond what the contract allows. Each has a different remedy.
Before you dispute anything, compare the extra cost against what a fair quote should have included in the first place.
When a Verbal Agreement Is Not Enough
A verbal agreement is difficult to enforce because it leaves no record of what was actually agreed. If your contract requires written instructions, a phone call approving extra work does not vary the contract, however clear the conversation felt at the time.
That cuts both ways. A builder who carries out extra work on a verbal instruction may struggle to recover the cost. A homeowner who verbally agrees to a change may find the price is not what they remember.
What to Agree Before Your Builder Starts on Site
The best time to resolve variation risk is before the first skip arrives. Get these agreed in writing:
- The variation procedure, named clause and who has authority to instruct changes
- How costs will be valued, whether by schedule of rates or dayworks
- The notice period required before extra work starts
If you are close to appointing a contractor, you can find out more about FMT Construction's services on our website, or contact us to discuss how we handle changes on your project.
Variation terms are the part of a building contract homeowners skim and later wish they had read. FMT Construction has over 35 years of practical experience and offers expertise in complex structural alterations, bespoke construction solutions and modern building methods, with safe and solid construction standards and long-lasting results.
Frequently Asked Questions
What is the difference between a contract variation and a change order?
A variation is the general term for any alteration to the agreed scope of work, used widely in JCT contracts. A change order is the formal written instruction that records that alteration, its cost adjustment and any time extension. In practice they describe the same event at different stages: the variation is the change itself, the change order is the paperwork that makes it contractual. Without the second, the first is just a conversation on site.
Can a builder charge extra for work not in the original contract?
Only where the extra work was properly instructed and agreed. If your builder carried out additional work without a written instruction or your approval, the position depends on your contractual terms and whether you accepted the work as it progressed. Verbal agreements can be binding in construction, which is exactly why you should confirm every instruction in writing the same day. If a charge appears without warning, ask for the written instruction, the priced breakdown and the contractual clause it relies on before paying anything.
How do change orders affect the final completion date of a renovation?
Every change order should state its time impact, not just its cost. Additional work, waiting for new materials or revised structural calculations can each push the project programme back, and if the delay is caused by instructed variations, a time extension is usually justified. Without that written time extension, you may find the completion date and any liquidated damages become a dispute. Ask your project manager to update the programme each time a change order is signed.
What happens if I refuse to sign a change order?
Refusing to sign means the work should not proceed, and your builder cannot recover the cost of uninstructed work through the final account. The correct step is to challenge the scope or the price in writing rather than simply ignoring the document. Ask for a breakdown, compare it to the original contract rates, and agree a revised figure. If no agreement is reached, most JCT and NEC contracts set out a notice and dispute resolution process you can follow.
