FIXED PRICE VS COST PLUS · VICTORIA
Fixed-Price vs Cost-Plus Building Contracts in Victoria
The contract pricing method changes how cost risk is shared between the homeowner and builder.
Short answer
A fixed-price contract sets an agreed contract price subject to the contract terms, approved variations and stated allowances. A cost-plus arrangement charges the actual cost of work plus an agreed builder fee or margin. In Victorian domestic building, cost-plus contracts are legally restricted, so homeowners should check current Consumer Affairs Victoria guidance and obtain independent legal advice before signing one.
What a fixed-price contract does
A fixed-price contract provides a defined contract sum for an agreed scope, drawings and specification. That does not mean the final amount can never change: approved variations, prime cost items and provisional sums can still affect the amount payable.
The clearer the documents are before signing, the less uncertainty is carried inside allowances and assumptions.
What cost-plus means
Under a cost-plus model, the project is charged from actual project costs together with the agreed builder fee or margin. This can be useful only in circumstances where the final scope genuinely cannot be priced reliably in advance.
Because the final cost is not fixed at contract signing, transparent records and a realistic estimate are particularly important.
Victorian domestic building law restricts cost-plus contracts
Consumer Affairs Victoria advises that cost-plus methods are restricted for domestic building work and recommends legal advice before signing this type of contract.
The rules can change, so use the current official guidance at the time the contract is prepared rather than relying on an old article or template.
Whichever method is used, define the scope
- ✓Contract drawings and specifications
- ✓Builder margin or fee where applicable
- ✓Prime cost and provisional sum allowances
- ✓Variations process
- ✓Progress payments
- ✓Site-cost assumptions
- ✓Records and supporting invoices where required
Questions homeowners ask
Does fixed price mean the price can never change?+
No. The contract can still change through lawful variations and adjustments to specified allowances such as prime cost and provisional sum items.
What is a cost-plus contract?+
It is a pricing method where actual project costs are charged together with an agreed builder fee or margin rather than one fixed construction price.
Are cost-plus contracts allowed in Victoria?+
They are restricted under Victorian domestic building law. Check current Consumer Affairs Victoria guidance and obtain legal advice before entering this type of contract.
Which contract gives more price certainty?+
A well-documented fixed-price contract generally provides greater upfront price certainty, provided the scope and allowances are clearly defined.
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Related EBC pages
- Building Contract Checklist Victoria
- Prime Cost Items and Provisional Sums
- Building Variations Explained
- Builder Quote vs Estimate