The cost of a construction variation is usually paid by the party responsible for the change. However, the answer depends on why the variation was needed, what the construction contract says and whether the additional work was properly instructed.
A client will normally pay when they request extra work, change the design or alter the agreed specification. A contractor may be responsible when work is required to correct their own error, defective workmanship or failure to follow the agreed plans.
Other situations, including unforeseen site conditions, design development and compliance requirements, can be less straightforward. In these cases, the contract, project records and cause of the change must be reviewed before responsibility can be established.
This article provides general construction guidance and should not be treated as legal advice. Professional advice should be sought where responsibility is unclear or significant costs are involved.
Who Pays For Variations In A Construction Project?
The client will usually pay for changes they request or for risks allocated to them under the construction contract. The contractor will generally be responsible for costs caused by their own errors, defective work or failure to meet their existing contractual obligations.
However, responsibility is not always straightforward. Unforeseen conditions, revised designs and compliance requirements may need to be reviewed against the contract before the parties can establish who should pay.
This article will cover:
- What is a construction variation?
- When does the client usually pay for a variation?
- When is the contractor responsible for the cost?
- Who pays for unforeseen construction work?
- Can a builder charge for work that was not approved?
- How are construction variations valued?
- Why written variation instructions are important
- How to prevent disputes over additional work
- When to involve a quantity surveyor
What Is A Construction Variation?
A construction variation is a change to the work originally agreed under a building contract.
Depending on the contract, it may also be described as a change order, variation order or compensation event. It can involve an addition, omission or alteration to the original scope of work.
Common examples include:
- Changing the design or specification
- Adding work that was not originally included
- Removing part of the agreed scope
- Altering materials, finishes or dimensions
- Changing the sequence or timing of the work
- Completing additional work following an unexpected discovery
Not every instruction is necessarily a variation. Some instructions may clarify work that was already included in the contractor’s obligations.
For example, asking a contractor to complete an item shown on the agreed drawings would not normally increase the contract value. Asking them to install a more expensive material than the one specified may be treated as a variation.
The distinction is important because it can affect whether the contractor is entitled to additional payment, extra time or both.
When Does The Client Usually Pay For A Variation?
The client will usually pay when they request a change that increases or alters the contractor’s agreed scope of work.
For example, the client may decide to:
- Change the internal layout
- Upgrade the agreed finishes
- Increase the size of an extension
- Add electrical points or additional fittings
- Replace one material with a more expensive alternative
The client may also be responsible when a variation results from revised information issued by their architect, engineer or design team.
These changes can increase the contractor’s labour, materials, plant, management and subcontractor costs. They may also affect the construction programme, particularly if materials have already been ordered or completed work must be altered.
However, the contractor should not simply carry out the additional work and add an unexplained charge to the final account.
The variation should follow the procedure set out in the contract. Wherever possible, the contractor should provide a quotation explaining the expected cost and programme impact before the work begins.
The client or authorised contract administrator can then approve, reject or amend the proposed change.
Professional contract administration can help ensure that variations are instructed, recorded and managed in line with the relevant contractual procedures.
When Is The Contractor Responsible For The Cost?
A contractor will not normally be entitled to additional payment for correcting their own mistake or completing work that was already included within their contractual obligations.
The contractor may be responsible where the extra work has been caused by:
- Defective workmanship
- Incorrect setting out
- Failure to follow the drawings
- Use of unsuitable materials
- Damage caused by the contractor
- Poor coordination of subcontractors
- An error within the contractor’s design responsibility
For example, if a wall is built in the wrong position and must be rebuilt, the cost would not usually be treated as a client-funded variation. It would normally be considered remedial work required to meet the original contract.
Responsibility can be less clear when the drawings, specification or tender documents contain missing or conflicting information.
The contractor may argue that the additional work could not reasonably have been identified when the price was prepared. The client may argue that an experienced contractor should have included it.
Professional quantity surveying services can help review the contract documents, pricing assumptions and project records to assess whether the contractor has a valid entitlement to additional payment.
Who Pays For Unforeseen Construction Work?
There is no single rule stating that the client or contractor must always pay for unforeseen construction work.
Responsibility depends on how the risk has been allocated in the contract and whether the condition could reasonably have been discovered before work began.
Examples of unforeseen conditions include:
- Hidden structural damage
- Unexpected ground conditions
- Unrecorded pipes, cables or drainage
- Asbestos or hazardous materials
- Defects concealed behind walls or floors
- Poor-quality historic construction work
In some contracts, the client retains responsibility for risks associated with existing buildings, incomplete information or hidden ground conditions. In others, the contractor may have accepted greater responsibility for inspecting the site and allowing for foreseeable risks.
The contractor should notify the client or contract administrator as soon as an unexpected issue is identified.
The notification should explain what has been found, why it affects the work, what action is required and the likely effect on cost and time.
Photographs, inspection reports, site records and correspondence should also be retained. These records may be important when deciding whether the condition was genuinely unforeseen and who should pay for the resulting work.
Can A Builder Charge For Work That Was Not Approved?
A builder may find it difficult to recover payment for additional work that was not properly instructed or approved.
Most formal construction contracts explain:
- Who is authorised to instruct variations
- How an instruction should be issued
- When the contractor must provide a quotation
- How the change will be valued
- How delays or additional time will be managed
If the contractor completes extra work without following the agreed process, the client may dispute whether the work was requested, necessary or chargeable.
However, a lack of formal approval does not automatically mean that payment will never be due. Emails, messages, meeting notes or the conduct of the parties may provide evidence that the change was requested or accepted.
Emergency work may also need to be completed before a formal instruction can be issued, particularly where action is required to prevent damage or protect health and safety.
Verbal instructions create greater risk because the parties may later disagree about what was requested. Contractors should confirm verbal discussions in writing before proceeding wherever possible.
The person issuing an instruction must also have the authority to approve the change. A request from someone who is not authorised under the contract may not provide the contractor with a clear entitlement to payment.
Effective contract administration can help ensure that instructions, approvals and contractual procedures are properly managed throughout the project.
How Are Construction Variations Valued?
Construction variations should be valued using the rules set out in the relevant building contract.
Where the varied work is similar to work already included in the contract, existing rates may be used. Where the work is different, adjusted or newly agreed rates may be required.
A variation valuation may include:
- Labour
- Materials
- Plant and equipment
- Subcontractor costs
- Site management and preliminaries
- Reasonable overheads and profit
- The effect of disruption or changed sequencing
The contractor should provide enough information to show how the proposed amount has been calculated. This might include supplier quotations, invoices, labour records, timesheets and subcontractor breakdowns.
Omissions should also be considered.
For example, if the client removes £8,000 of work and replaces it with £12,000 of alternative work, the overall adjustment should normally reflect both the addition and the omission.
Variations can also be reviewed as part of regular construction valuations. This helps the project team understand how approved changes affect interim payments and the forecast final cost.
Why Written Variation Instructions Are Important
Written variation instructions provide a clear record of what has changed, why it has changed and who authorised it.
A suitable variation record should include:
- A clear description of the change
- Relevant drawings or specifications
- The reason for the variation
- The date it was requested
- The person who approved it
- The estimated or agreed cost
- Any effect on the completion date
- The current approval and valuation status
This gives the client greater control over the budget and helps the contractor understand exactly what must be delivered.
Written records are particularly important because the impact of a variation may extend beyond the immediate work.
Changing a material may create cancellation charges or longer lead times. Moving a wall may affect electrical, plumbing, flooring and decorating work. A late design decision may disrupt the contractor’s planned sequence.
Recording these effects when the variation is instructed makes it easier to assess the true financial and programme impact.
The parties should also maintain a live variation register. This should show whether each change has been requested, priced, approved, completed and included within the latest project forecast.
How To Prevent Disputes Over Additional Work
Clear documentation and consistent change control can significantly reduce the risk of variation disputes.
The project should begin with detailed drawings, specifications and scope documents explaining what is included in the contractor’s price. Assumptions, exclusions and provisional allowances should also be clearly identified.
A detailed cost plan can help establish realistic project allowances and identify financial risks before construction begins.
During the project, each variation should follow a clear process:
1. Identify The Proposed Change
The project team should clearly explain what is changing and why the change is required.
2. Review The Original Scope
The drawings, specification, contract documents and contractor’s quotation should be checked to confirm whether the work is genuinely additional.
3. Assess The Cost And Programme Impact
The contractor should provide a breakdown of the expected cost and explain whether the change will affect procurement, sequencing or completion.
4. Obtain Written Approval
The variation should be approved by the person authorised under the contract before the work begins wherever possible.
5. Update The Variation Register
The project cost forecast should be updated to show the latest approved, pending and potential variations.
6. Agree The Final Value Promptly
The parties should avoid leaving every variation until the final account. Delayed agreement can result in missing records, disputed memories and unexpected costs.
Where a disagreement arises, the parties should first review the contract, original pricing documents, instructions, quotations and site records.
Specialist construction dispute resolution support may be required where the parties cannot agree whether a variation is valid, who is responsible or how much should be paid.
When To Involve A Quantity Surveyor
A quantity surveyor can support the project team before construction begins, throughout the work or when a specific variation dispute arises.
Their role may include:
- Reviewing the original scope and contract
- Assessing contractor quotations
- Maintaining a variation register
- Valuing additions and omissions
- Updating the forecast final cost
- Reviewing supporting cost records
- Supporting interim valuations
- Negotiating the final account
- Providing an independent view on disputed costs
A quantity surveyor should be involved promptly when a variation is substantial, affects several areas of the project or may delay completion.
Early involvement can also help prevent disputes by ensuring that changes are properly recorded, priced and approved before the work is carried out.
Through professional quantity surveying services, the project team can gain a clearer understanding of the commercial effect of each change and maintain greater control over the final project cost.
Who Ultimately Pays For Construction Variations?
The client will normally pay for changes they request or for risks allocated to them under the contract.
The contractor will generally be responsible for correcting their own errors, defective workmanship or failure to meet their existing obligations.
For unforeseen conditions, design changes and compliance-related work, responsibility depends on the contract, the reason for the change and the available evidence.
The main points to remember are:
- Client-requested additions are normally paid for by the client.
- Contractors are generally responsible for correcting their own mistakes.
- Unforeseen work depends on how risk is allocated under the contract.
- Additional work should be properly instructed and approved.
- Variations should be supported by clear cost records.
- Additions and omissions should both be reflected in the valuation.
- A live variation register should be maintained throughout the project.
- Professional advice should be obtained where responsibility is disputed.
So, who pays for variations in a construction project? The answer will depend on who caused or requested the change, the terms of the building contract and whether the correct contractual process was followed.
Written instructions, accurate records and regular cost reporting allow the parties to understand the financial impact of each change as the project progresses rather than facing unexpected costs at the end.
Bhangals Construction Consultants can support clients, developers, contractors and professional teams with variation management, quantity surveying, valuations, cost planning and contract administration.
Speak to our team for greater clarity and control over construction variations, additional costs and the final account.