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's real cost is rarely just the work itself — it is that work plus the builder's margin, applied to a decision made under time pressure rather than during design.
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
Every item on that list is really the same instruction in different forms: resolve decisions during design, not during construction. See why rushing the design phase costs you more for why that instinct to move faster is exactly what produces the gaps variations come from.
And if a variation price itself will not move once raised, see builder won't negotiate contract changes for what is actually happening on the other side of that conversation.
Frequently asked questions
Are variations always the client's fault?
No. Incomplete documentation and unforeseen site conditions cause plenty of variations that have nothing to do with a change of mind.
What single change reduces variations the most?
Locking finish selections and completing the design before going to tender — decisions made under construction time pressure are the most expensive kind.
Already facing a variation you did not expect?
Realignment finds a way back to budget without abandoning the design you started with.
A structured way to recover cost once a project has already drifted.