Remeasurement and approximate quantities

Where a bill of quantities includes items marked as approximate quantities, those items are not a firm commitment. The work is measured as it is actually executed and valued at the rates in the bill. That is the whole mechanism, and for most items it works without anyone thinking about it.

The rate is the point

The reason approximate quantities are used is that the design is not developed enough to measure firmly, but the nature of the work is known well enough to price. Excavation depths, drainage runs, ground remediation: the item is understood, the extent is not.

Because the rate is agreed and only the quantity is open, remeasurement is usually straightforward. Measure what was done, apply the rate, done.

Where it stops being straightforward

Under JCT, where the approximate quantity is not a reasonably accurate forecast of the quantity actually required, the valuation rules require a fair allowance for the difference.

That matters because rates are quantity-sensitive. A rate for two hundred metres of drainage carries a share of mobilisation, setting out and supervision that does not double when the quantity doubles, and does not disappear when it halves.

Both directions

The adjustment cuts both ways, which is worth saying because it is usually raised by contractors when quantities fall short and by employers when they overrun.

If a quantity comes in at four times the bill figure, the contractor may be over-recovering on fixed elements built into the rate. If it comes in at a quarter, it may be under-recovering on the same elements. A fair allowance is a fair allowance in either direction.

What reasonably accurate means

There is no percentage in the contract, and there is no useful rule of thumb. A twenty per cent movement on a large, simple item may change nothing about the appropriateness of the rate. A twenty per cent movement on a small item with heavy mobilisation may change it completely.

The test is whether the rate remains a reasonable basis, not whether the quantity moved by more than some threshold.

Record the measure, not just the total

Remeasured work is checked long after it is buried. The dimension sheets, the site records and the agreement of the measure at the time are what make it stand up. A total with no supporting measure is not a remeasurement, it is an assertion.

Agreeing the measure jointly as the work proceeds costs an hour a month and removes the single most common source of final account argument on remeasured contracts.

In interim valuations

Approximate quantities are valued on the work actually executed to date, at the bill rate, in the ordinary way. What should not happen is valuing at the bill quantity because the item is nominally complete. The bill quantity was always an estimate; only the measure is real.