Why a unit rate prices a small job too cheap
A unit rate is what one more of something costs once you are there. On a small job almost all of the cost is being there at all.
A unit rate is the most useful number in estimating and the most dangerous one on a small job. It answers a precise question — what does one more cubic metre cost, once the gang is on site and the machine is working — and it answers nothing at all about the cost of getting there. On a job with four hundred cubic metres of dig that distinction does not matter, because the mobilisation is a rounding error against the measure. On a job with 1.7 cubic metres it is the entire price.
1.7m³ of pad excavation at £90 a cubic metre is £152. Nobody brings a machine and a banksman to a churchyard for £152. 1.35m³ of GEN3 at £280 is £378, and the ready-mix lorry has a minimum load which it charges for whether you take it or not. Price a garden room, a boundary wall or a single pad off unit rates alone and the quotation comes out too cheap to deliver — not because the rates were wrong, but because they were answering a different question.
What a minimum charge actually covers
The delivery. The minimum load. The half day a two-man gang cannot sell to anybody else. The plant hire that comes in day units whether you need six hours or two. The trip to the tip. The setting out. Every one of those is a real invoice and none of them scales with the measure.
Any estimator who has priced small works knows this and prices it in their head. What they rarely do is write it down in a way that survives being handed to somebody else, or to a spreadsheet, or to software — and that is where it gets lost. A rate library holds rates. It has nowhere to put "and the least this costs at all is four hundred pounds".
Pricing the line at whichever is greater
CONSTRUX holds both against every measured line: the rate, and the least the item costs to do at all at the quantity measured. The line is priced at whichever is greater, and where the minimum carried it the estimate says so by name rather than folding it silently into a number nobody can reconcile against the rate beside it.
Two rules keep it honest. It never touches a line with no rate against it — a minimum charge there would replace a visible gap with a plausible number, and a plausible number is not questioned. And where it lifts a line, the uplift goes on in the proportions that line is already priced in, so a groundworks minimum stays in groundworks rather than appearing as a site-wide cost nobody can trace.
Where the number comes from
From the same place as the rate. Where the business has priced the work before, its own committed rates answer both questions. Where it has not, the market view it asks for includes the minimum — and both are labelled as a market view everywhere they appear, kept out of the rate history, and put in front of a person to keep or change before anything is sent to a customer.
It is one field. On a small-works contractor pricing two jobs a week, it is the difference between a quotation that makes money and one that wins. The demonstration project prices a churchyard retaining wall end to end if you want to watch it happen.
See the record being made rather than described.
Launch the demo environment