The 3 kinds of variations
- Owner-requested: You changed something. Legitimate cost. Pay it.
- Site-condition variations: Something on-site was different than assumed (rock, soft soil, hidden asbestos). Legitimate IF the assumption was reasonable at contract signing.
- Provisional sum "true-up": The actual cost came in higher than the allowance. Legitimate ONLY if the allowance was set with genuine market data - watch for lowball allowances used to win the contract.
Push back on these
- Charges for work already in your fixed-price contract
- Variations quoted without a written cost breakdown
- Any variation that appears AFTER the work is done ("we assumed you wanted...")
- Provisional sum blow-outs on items where market pricing hasn’t moved since your contract
How to negotiate
Every variation needs a written cost breakdown BEFORE work starts. Ask for the labour hours, the material cost, the supplier quote. If the builder cannot itemise it, they cannot enforce it. Get everything in writing.