Building Variations: Why They Happen and What They Cost
Variations are not bad luck. They are the predictable consequence of decisions not made during design, documentation gaps the builder encounters on site, and changes of mind during construction.
A variation is any change to the scope, specification, or programme of a building contract after it has been signed. The cumulative cost of variations is one of the most reliable predictors of whether a project finishes on budget.
Why variations happen
- Incomplete documentation — where drawings or specification do not define something clearly, the builder makes an assumption. When expectations differ, a variation is raised.
- Client-initiated changes — decisions made during construction to change something already agreed. These are entirely avoidable if design decisions are locked before construction begins.
- Unforeseen site conditions — rock, contaminated soil, hidden services, structural issues in existing buildings.
- Latent conditions in existing buildings — asbestos, termite damage, structural deterioration not visible until demolition.
What variations actually cost
When a builder prices a variation, they apply their margin — typically 15 to 20 percent — to the cost of the work. A variation for $10,000 of actual work costs $11,500 to $12,000.
How to minimise variations
- Complete your design before going to tender
- Attach a specification to the contract
- Lock finish selections before construction commences
- Include a realistic contingency — 5 to 10 percent of contract value
Already feeling the budget pressure?
If your project has drifted beyond budget, realignment can bring it back.
We help homeowners, architects and developers recover cost and buildability without losing the design they set out to build.