Three percentages, not one
The contract states separate additions for labour, materials and plant because they cover different things. Applying an average to the lot is quick, and it is the reason the sheet comes back.
QScope Team · 19 February 2026 · 4 min read
Daywork is for work that cannot properly be valued by measurement at contract rates. The valuation is built from the prime cost of labour, materials and plant, with a percentage addition to each to cover overheads and profit.
Those percentages are stated separately in the contract particulars, and they are usually quite different from each other. Labour additions of well over a hundred per cent are common; materials and plant additions are typically much lower.
Why they differ so much
The percentages are not a uniform mark-up. Each covers a different set of costs that the prime cost figure excludes.
On labour, the addition covers employment costs beyond the wage: national insurance, holiday pay, pension, training levy, supervision, small tools, insurance, plus overheads and profit. That is a substantial list, hence a substantial percentage.
On materials, most of the cost is already in the invoice. The addition covers handling, waste, storage and financing, plus overheads and profit. A much shorter list.
Plant sits somewhere between, depending on whether it is hired or owned.
What blending actually does
Take a sheet with two thousand pounds of labour, three thousand of materials and five hundred of plant, and suppose the contract states additions of 130, 15 and 20 per cent.
Applied correctly the total is £4,600 on labour, £3,450 on materials and £600 on plant: £8,650. Applied as a single blended 55 per cent across the £5,500 prime cost, the total is £8,525. Close enough to look right, far enough apart to be argued about, and on the next sheet with a different mix the error runs the other way and is larger.
The problem is not the size of the discrepancy. It is that the figure cannot be checked, so every sheet becomes a negotiation instead of a calculation.
What the prime cost includes
Where the contract adopts the RICS definition of prime cost of daywork, that document decides what goes into the base figure before any percentage is applied. Reading it once is worth doing, because a percentage applied to the wrong base is wrong however carefully it is applied.
Records are the other half
Daywork stands or falls on contemporaneous records: who was on site, for how long, what plant was used, what materials went in, signed at the time by someone with authority to sign.
Sheets submitted weeks later, unsigned, reconstructed from memory, are the hardest money on any job to recover. Not because anyone doubts the work happened, but because nobody can now establish what it took.
Agreed is not the same as submitted
Only agreed sheets belong in the final account. Carrying submitted sheets as though they were agreed inflates the account and destroys confidence in the rest of it, which is a poor trade for a figure that was always going to be tested.
QScope applies each addition to its own element and shows the sheet total with the workings, so the figure being submitted is the figure that was agreed.