Variation Order Cost Calculator

Because three things are missing: the instruction showing who ordered the change, evidence it happened — photographs, inspection records, delivery notes — and the build-up showing why that rate. Auditors work on no instruction, no claim; no evidence, no measurement; no build-up, no price. The classic mistake is doing the work first and signing afterwards, when the client is no longer in a hurry and the leverage has flipped.

Three cases: no identical or similar item exists in the bill; the quantity changes by more than 15% so the rate becomes unreasonable at the new volume; or a design change alters the method or specification materially. Otherwise the original rate stands. Re-pricing needs a labour, material and plant build-up, and auditors check consumption and market rates line by line, cutting anything inflated.

A design change is a drawing revision issued by the designer and confirmed by the client, with formal paperwork; a site instruction records small or temporary work on the spot — hitting an obstruction, temporary propping, acceleration measures. Both are valued at settlement, but site instructions carry a higher evidential bar because they confirm after the event, so they are the first thing questioned in audit. Sign them the same day, with photographs.