MethodUnit rate build-up
CurrencyNGN (₦)
Worked exampleLagos
Figures dated25 August 2026

Build a unit rate you can explain and defend

A rate is not a number you remember. It is materials, labour, plant, waste, productivity, overheads and profit — assembled, dated and located. Here is the whole arithmetic for one cubic metre of concrete.

Save this build-up in BillMate Then keep it in a library
Written byThe BillMate product teamProduct and documentation
Last reviewed
Correctionssupport@billmate.site

The ten things a defensible rate states

Most disputes about a rate are not disputes about the number. They are disputes about what the number was supposed to include. A rate that states these ten things is arguable; one that does not is only assertable.

The ten components of a defensible unit rate.
ComponentWhat it meansWhere it goes wrong
MaterialsDelivered cost at the site gate, in the unit you actually buy in — cement by the bag, granite by the cubic metre.Using an ex-works price and forgetting haulage, or pricing in a unit you do not buy in.
WasteThe gap between what is delivered and what ends up in the work. Carried in the constituent quantity, not bolted on afterwards.A single blanket percentage across every material. Cement waste and granite waste are not the same problem.
LabourGang cost per hour, multiplied by the hours the operation actually takes.Pricing a day rate against a per-m³ item without converting through an output.
ProductivityThe output — how much of the item one gang produces per hour. This is the number that makes labour a rate rather than a guess.Borrowing an output from a textbook without asking whether it assumed your site access, your gang and your supervision.
PlantHire, fuel and operator, at the utilisation the item actually uses — a mixer serving several items is not fully charged to one.Charging a full day of mixer hire to a single item that used it for two hours.
OverheadsSite establishment and head-office costs recovered across the work, as a stated percentage.Recovering the same overhead twice — once in preliminaries and again in every rate.
Profit and riskThe return, stated as a percentage on net cost plus overheads, and visible.Hiding it inside the material prices, which makes the whole rate unarguable.
LocationThe city, and often the part of it. Lagos Island access is not Ibadan access.A national rate. There is no such thing.
Pricing dateThe month the constituent costs were true.Reusing a rate whose date nobody recorded. This is the single most common failure.
Source and verificationWhere the figure came from — a quotation, a priced tender, your own build-up, or an AI draft — and whether a human has checked it.A machine-drafted figure that has quietly become “our rate” through repetition.
Worked example

Reinforced concrete grade 25 in ground beams, per m³.

Every line, every multiplication, and the two percentage additions at the end.

Reinforced concrete grade 25 in ground beams — unit rate per m³
Unit rate build-up for Reinforced concrete grade 25 in ground beams: constituent, quantity, unit, unit cost and amount, with percentage additions.
Constituent Quantity Unit Cost Amount
Material Cement, 42.5N — 7.0 bags/m³ including 5% waste 7.35 bag ₦9,800 ₦72,030
Material Sharp sand — 0.44 m³ including 8% waste 0.48 m³ ₦22,000 ₦10,560
Material Granite 19 mm — 0.88 m³ including 8% waste 0.95 m³ ₦48,000 ₦45,600
Material Water, curing and admixture allowance 1.00 item ₦1,500 ₦1,500
Labour Mason gang — mix, place, vibrate and finish 1.60 hr ₦4,500 ₦7,200
Labour Labourer — batching and handling 4.80 hr ₦2,200 ₦10,560
Plant Concrete mixer, 0.4 m³ — hire, fuel and operator 0.55 hr ₦6,500 ₦3,575
Plant Poker vibrator — hire and fuel 0.35 hr ₦3,000 ₦1,050
Net cost₦152,075
Overheads and establishment charges, 10%₦15,207.50
Profit and risk, 15% on net cost plus overheads₦25,092.38
Unit rate per m³₦192,374.88

Read this before using any figure above. These constituent costs are an illustration of the method for Lagos as at 25 August 2026. They are not a market survey, not a quotation and not current evidence — Nigerian material prices move fast enough that a figure published on a website is out of date by the time you read it. Re-price every line against your own suppliers. Our position on published figures.

How each line was arrived at

  1. Cement — 7.0 bags/m³, plus 5% waste = 7.35 bagsA 1:2:4 mix by volume at grade 25 works out near seven 50 kg bags per cubic metre. The 5% covers part-bags, spillage at the mixer and the bags that harden in store before use. If you batch by weight and store under cover, argue for less.
  2. Sharp sand — 0.44 m³, plus 8% waste = 0.48 m³Waste here is bulking, spillage off the stockpile and the material left in the heap that never makes it into a mix. On a tight urban site with a hard standing, less; on an open site with a soft stockpile, more.
  3. Granite 19 mm — 0.88 m³, plus 8% waste = 0.95 m³Same logic as the sand. Note that sand and granite volumes sum to more than a cubic metre — that is not an error, it is the voids ratio: the mixed and compacted volume is less than the sum of its loose components.
  4. Mason gang — 1.6 hours per m³This is the productivity assumption, and it is doing more work than any other number in the table. It assumes mixing on site, placing by barrow within a reasonable haul, and a gang that has been on the job long enough to have found its rhythm. A first pour, a difficult access or a congested reinforcement cage all push it up.
  5. Labourer — 4.8 hours per m³Three labourers to the gang, over the same 1.6 hours. Batching, charging the mixer, barrowing, and clearing up afterwards.
  6. Mixer — 0.55 hours per m³Utilisation, not duration. The mixer is hired by the day and serves the whole pour; this item carries the proportion of its running time that this concrete actually consumed. Charging the full day here and again on the next item is how a bill quietly doubles its plant recovery.
  7. Poker vibrator — 0.35 hours per m³Same principle. Compaction time per cubic metre, not the time the poker sat on site.
  8. Overheads at 10%On net cost. Check this against what you have already recovered in preliminaries — recovering the same establishment cost twice is the most common way a bill prices itself out of a tender.
  9. Profit and risk at 15%On net cost plus overheads, so profit is earned on the overhead recovery as well. State it openly. A rate whose profit is hidden inside its material prices cannot be defended line by line, which is the whole purpose of doing this.
Afterwards

A build-up is only useful if it survives the job

The rate above took twenty minutes to assemble. Doing that again from scratch on the next project is the waste. In BillMate the finished build-up saves into your rate library carrying its city, its month and its source — so next time it is a starting point with a known age rather than a number in an old workbook.

  • Save the build-up to the library, with its constituents intact and reopenable
  • The location and pricing month travel with it
  • After 12 months it is flagged stale rather than reused silently
  • A controlled percentage uplift is recorded as provenance, not applied invisibly

Building and maintaining a Nigerian rate library

The build-up, once saved
Rate library extract: description, unit, rate, location, month priced, source and currency status.
Description Unit Rate Location Priced Source Status
Excavate trench n.e. 1.50 m deep, deposit spoil on site m³ ₦4,500 Lagos — Lekki 2026-05 Priced tender Current
225 mm hollow sandcrete blockwork in walls, 1:6 mortar m² ₦8,200 Lagos — Ikeja 2026-06 Priced tender Current
Reinforced concrete grade 25 in ground beams m³ ₦182,400 Lagos — Lekki 2026-04 Own build-up Current
High-yield reinforcement, 12 mm, cut, bent and fixed kg ₦2,350 Abuja — Gwarinpa 2025-02 Priced tender Stale

Where AI fits, and where it does not

AI drafts; the Quantity Surveyor verifies.

BillMate's AI assistant can suggest a build-up structure for an item you have not priced before — which constituents belong in it, roughly what output to assume. That is genuinely useful, and it is the part of the work that is mostly recall.

What it cannot do is tell you what a bag of cement costs in Ikeja this month. A model produces that figure from training data of uncertain age and unknown local weighting, and it will produce it confidently whether or not it has any basis. BillMate marks every AI rate as unverified, and prints the count of unverified rates on the exported bill where the client's surveyor can see it.

Use a draft to keep working while you chase the real price. Do not let it become "our rate" through repetition. How the assistant works · What it is allowed to do.

Want to try the arithmetic without installing anything? The unit rate build-up calculator on QS Fieldbook runs in the browser with every assumption on screen — material, labour, plant, overheads and profit — and shows the same arithmetic this page sets out. It is free and there is nothing to sign up for.

Build one rate and see whether it holds up.

Rate build-ups are free — they are part of the 2-project free tier, not the licence.

Try this workflow freeView a sample BOQ