Dayworks rate calculator
Build a daywork claim the way a contract values it: the prime cost of labour, materials, and plant, plus the percentage additions agreed in your contract. Works for JCT building contracts, CECA civil engineering schedules, and NEC4.
Daywork is the method a construction contract uses to value extra work that cannot be measured and priced from the bill rates: small variations, unforeseen ground, opening up, or attendance on others. Instead of a measured rate, the work is valued at its prime cost (the actual cost of the resources used) plus a percentage addition for overheads and profit. This calculator builds that figure for you from the prime cost of labour, materials, and plant, with an optional travel and subsistence section for remote jobs where the crew has to stay away from home.
Daywork claim builder
Pick the contract basis, enter the resources used, and set the percentage additions from your contract. The claim updates live.
Indicative only. The percentage additions, discount rules, whether plant carries its operator, and how remote costs are categorised are set by your contract, not by this tool. Always price from the definition and rates named in your contract documents, and submit signed daywork sheets promptly.
Which daywork definition applies
The contract you are working under decides how daywork is valued. Pick the basis in the calculator to highlight the one that applies to you.
JCT building contracts
Work that cannot be properly measured is valued as daywork under the variation rules (for example clause 5.7 of JCT SBC/Q 2016).
It uses the RICS Definition of Prime Cost of Daywork with percentage additions to labour, materials, and plant. Those percentages are stated by the contractor in the contract documents at tender.
Civil engineering (CECA)
ICE and NEC civil works commonly benchmark daywork against the CECA Schedules of Dayworks (3rd edition, August 2025).
CECA labour and plant rates already bundle most oncosts, so the percentage you add on top is usually small. Watch for double-counting overheads that are already in the schedule rate.
NEC4 ECC
NEC4 has no separate daywork mechanism by default: a compensation event (the NEC term for a change that may alter price or time) is assessed on Defined Cost plus the Fee.
People rates come from Contract Data Part 2 and the Fee percentage covers overheads and profit. Use the build-up above with the Fee in place of the percentage additions.
How each prime cost head is built up
Prime cost is the actual cost of the resource before overheads and profit. The percentage addition is what turns prime cost into a price.
Labour: the all-in rate
The all-in hourly rate is the real cost of putting an operative on site, not just their take-home pay. It builds up from basic pay plus:
- • Employer's National Insurance
- • Holiday pay and pension
- • CITB levy (the training board charge on the wage bill)
- • Employer's liability insurance
- • Non-productive time and travel
The labour percentage addition then covers site overheads, supervision, and profit, which is why it is far larger than the materials or plant addition.
Materials: net cost
The prime cost of materials is the invoice cost delivered to site, after deducting all trade discounts but not cash discounts of up to 5%.
Add unloading, storage, and waste where they are not recovered elsewhere. The small percentage addition covers handling and profit.
Plant: hire or use rate
For hired plant, prime cost is the actual hire invoice. For owned plant, it is the rate in the contract schedule (for example the CECA or CPA rates the contract names).
Confirm whether the rate includes fuel, the operator, and standing time before you price it, so nothing is charged twice.
Travel & subsistence
On remote jobs, travelling time, fares, mileage, and lodging may be recoverable, but the contract definition decides whether they sit in labour, incidental costs, or a separate reimbursable head.
This calculator shows them separately for review. Civil engineering crews commonly use the CIJC away-from-home allowance per night and HMRC approved mileage where the contract allows it.
Typical percentage additions
These bands are illustrative ranges seen in quantity surveying practice, not fixed rates. The actual figures are agreed in your contract. Change a percentage in the calculator to highlight its row; a value outside the typical band is flagged so you can double-check it.
| Resource head | Typical addition | What it covers |
|---|---|---|
| Labour | ~40–80% | Site overheads, supervision, non-productive time, head office costs, and profit. Main contractors often pre-state a figure of around 50%. |
| Materials | ~5–10% | Handling, storage, minor waste, and profit on the net invoice cost. |
| Plant | ~5–10% | Overheads and profit on the hire or schedule rate. Lower or nil where the schedule rate already includes them. |
| Travel & subsistence | ~0–5% | Mileage, fares, and lodging on remote jobs. Often passed through at net cost, but apply the percentage or labour addition your contract states. |
Source: quantity surveying practice commentary (see sources below). Ranges are indicative only and contractor-specific.
Worked example
A half-day of unforeseen drainage work, valued on a JCT building basis with a 50% labour addition and 10% on materials and plant. These figures match the calculator's starting values.
| Labour | ||
| Ganger / working foreman | 8 h × £32 | £256.00 |
| Skilled operative | 8 h × £26 | £208.00 |
| General operatives | 16 h × £22 | £352.00 |
| Labour prime cost | £816.00 | |
| Plus 50% addition | £1,224.00 | |
| Materials | ||
| Pipe, bedding, fittings (net) | + 10% | £250.00 → £275.00 |
| Plant | ||
| Excavator (machine only) | 4 h × £38 | £152.00 |
| Tracked dumper | 4 h × £20 | £80.00 |
| Plant prime cost | £232.00 | |
| Plus 10% addition | £255.20 | |
| Total daywork value | £1,754.20 | |
Getting a daywork claim paid
The price is only half the job. Dayworks fail on records, not arithmetic.
Get sheets signed the same day
A signed daywork sheet records the resources, not their value: who worked, for how long, what plant stood, and what materials went in. Get it signed by the client's agent at the end of each shift while the facts are fresh. A signature "for record purposes only" still proves the resource even if the rate is disputed later. Unsigned sheets are the most common reason daywork is rejected.
Daywork is the last resort, not the first
Most contracts only allow daywork where the work genuinely cannot be measured and valued at bill or pro-rata rates. If a measured rate exists or can be derived, the contract administrator can insist on it. Flag work as daywork before you start it, and confirm in writing that the client agrees it will be valued that way.
Do not double-count overheads
CECA schedule rates and many plant hire rates already include head office overheads and, in some cases, profit. If you then apply a full overhead-and-profit percentage on top, you are charging for the same thing twice and the claim will be cut. Read what the rate already contains before you add a percentage to it.
Standing time and the operator
Plant that is held on site but idle because of the change can often be claimed as standing time, usually at a reduced rate set by the contract. Be clear whether your plant rate includes the operator: if the driver's hours are already in the labour section, do not include them again in the plant rate, or the claim will be reduced for duplication.
Sources
- RICS Definition of Prime Cost of Daywork carried out under a Building Contract (3rd edition, operative 1 September 2007), the labour, materials, and plant basis used by JCT contracts.
- Building: revised daywork definition, background on the 2007 RICS definition and its labour pricing options.
- JCT SBC/Q 2016 contents, showing clause 5.7 on valuing work that cannot be properly measured (HM/JCT).
- Designing Buildings: Dayworks, the prime cost plus percentage addition structure explained.
- Ramskill Martin: Daywork, what it is and how it should be priced, on percentage additions being contract-stated and typical materials and plant additions.
- CECA Schedules of Dayworks (3rd edition, August 2025), the civil engineering daywork rate schedules.
- Metroun: what are CECA rates, on CECA rates in NEC Defined Cost and avoiding double-counting overheads.
- NEC: Defined Cost in NEC4 ECC, how compensation events are assessed on Defined Cost plus the Fee.
- UK Estimating Support: prime cost of labour addition, a worked build-up of the all-in labour rate and labour percentage.
- CITB current levy rates, the training levy element of the all-in labour cost.
- CIJC Working Rule Agreement allowances (HMRC EIM71325), the lodging or overnight subsistence allowance (£51.97 per night from 30 June 2025) and CIJC travel allowance tables.
- HMRC approved mileage allowance payments, cars and vans at 55p per mile for the first 10,000 business miles in tax year 2026/27, then 25p.
Built by Rospower Projects, a UK groundworks and civil engineering contractor working under JCT and NEC contracts.
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