Most bills of quantities do one job and then stop. They are prepared, they are used to get prices, a contractor is chosen, and the document goes into a folder nobody opens again until there is an argument.
That is a waste of the most useful thing on the project.
What it actually is
A bill of quantities is a measured list of everything the works require: so much excavation, so many blocks, so much reinforcement, so much roofing, priced per unit. Two numbers per line: how much, and what each costs.
The pricing half is what everybody uses. The measurement half is what makes cost control possible, because it is the only place that says what the build should consume before it consumes it.
Why that matters mid-build
Without a measured expectation, the question "are we over budget?" can only be answered by adding up what has been spent, which tells you where you are but not whether that is where you should be. Half the money gone at half the build is meaningless on its own: it depends entirely on which half.
With one, the question becomes answerable weekly. This element was measured at this quantity; we have consumed that much; we are that far through it. Now spending has a denominator, and an overrun announces itself in week six rather than at handover.
How to make yours useful
Keep it in a form you can compare against. A priced PDF from the quantity surveyor is a record. The same figures in a sheet, element by element, is a control. Whatever you use has to let you put actual next to planned.
Record deliveries against elements, not just in total. Cement received is a number. Cement received against the blockwork element is information. See why materials go missing on site for the receiving discipline this depends on.
Update it when the design changes. A variation that is agreed but never reflected in the bill turns your baseline into fiction, and every comparison after that point is meaningless.
Look at the variances, not the totals. Three elements will be badly out and the rest will be close. Find the three.
The most common failure
Not that the bill is wrong. It is usually a reasonable measurement of a reasonable design. It is that nobody compares anything to it until the project is finished, at which point it becomes a document for arguing about rather than a tool for deciding.
The habit worth building is small: once a week, take the elements currently in progress and put actual next to planned. Ten minutes. It is the entire difference between knowing and hoping.
This is what Build is designed around: a bill of quantities that stays live, with goods-received notes and labour posting against elements, and budget-versus-actual updating as the site spends. The weekly comparison works on paper too, though, and it is worth starting on your current project rather than your next one.
Who prepares a bill of quantities in Kenya
A bill of quantities is normally prepared by a quantity surveyor working from the architect's and engineer's drawings. On a private house the same person often also advises on the contract, values work done on site and prepares the final account, which is why the fee is usually quoted against the whole project rather than the document alone.
A contractor can produce a measured breakdown too, and many will if you ask. It is not the same thing, and the difference matters: a contractor measures the work they intend to be paid for, using their own assumptions about ground conditions, wastage and sequencing. An independent measure carries no such interest. The practical trade-off between the two is set out in full in bill of quantities vs a contractor's quote.
The fee question is the one that stops most self-builders. It is worth framing correctly: the BQ is not competing with tiles or windows for the budget. It is competing with the overrun it is supposed to detect, and on a build of any size the overrun is the larger number.
How to read one as a homeowner
A bill is organised by element, in the order the works happen, and you do not need to understand the measurement rules to read it usefully. Four things to look at:
The preliminaries. The first section covers site set-up, temporary works, supervision, insurance, water and power on site: everything that is not part of any wall. Owners skim it because nothing in it is visible in the finished house. It is frequently a significant share of the contract sum, and it is where a thin quote hides its optimism.
The quantities, not the rates. A rate that looks high is a negotiation. A quantity that looks wrong is a problem, because every price in that line is multiplied by it. Check the ones you can check: floor area, wall lengths, number of doors and windows.
Anything not firmly measured. A provisional sum is an allowance for work that has not been specified precisely yet, and it is expected to be adjusted to whatever the work actually costs. A prime cost sum works the same way for a supplier's item, such as fittings or ironmongery, that has not been chosen. A contract sum resting on several generous allowances looks firm and is not.
The exclusions. Read what the document says it does not cover. External works, boundary wall, gate, driveway, drainage and connections are routinely outside the measured works and inside your actual budget.
What a bill of quantities does not tell you
It measures the design that existed on the day it was prepared. It does not know that the ground turned out to be rock, that you changed the roof, or that the steel price moved between tender and the second floor slab.
That is not a fault in the document. It is the reason a bill has to be maintained rather than filed. Every approved variation order changes the baseline, and a baseline that is not updated stops being a measure of anything by about the third change. Keeping the adjusted contract sum current is the single habit that separates builds that know where they stand from builds that find out at the final account.
It also says nothing about time. A project can be exactly on budget per element and four months late, and late costs money in ways the bill never measures: rent you are still paying, financing you are still servicing, a contractor still standing on site.
Turning the bill into a weekly control
The whole point of the measurement half is that it lets you ask, this week, whether spending is where it should be. A worked version of that comparison, for one element:
- Take the element currently in progress, say blockwork to the ground floor.
- Read the measured quantity and rate from the bill. That is what it was supposed to cost.
- Ask the site what proportion of that element is complete. Walls up to lintel level on three of four elevations is roughly three-quarters, and roughly is enough.
- Add up what has actually been spent on it: materials counted in via a goods received note, labour posted to that element, plant hire.
- Compare. Three-quarters of the element for four-fifths of its budget is a small, early, fixable signal. The same ratio discovered at handover is a bill.
Do that for the two or three elements in progress and you have a budget-versus-actual position in about ten minutes a week. Every piece of construction cost control software worth paying for is automating exactly this loop, including ours. What it adds is that the comparison stays current between your weekly sittings, and that nobody has to remember to do it.
Common questions
Who prepares a bill of quantities in Kenya?
A registered quantity surveyor, working from the architect's and engineer's drawings. Contractors prepare priced breakdowns of their own, which serve a different purpose and carry their assumptions rather than an independent measure.
How much does a bill of quantities cost?
It is normally a percentage of the project value and quoted as part of a wider quantity surveying service covering measurement, tender documentation, valuation of work done and the final account, rather than as a standalone document. Get the scope in writing: a fee that includes monthly valuations is worth considerably more than one that ends when the document is delivered.
Can I just use the contractor's quote instead?
You can, and on a small extension it may be proportionate. Insist on a measured breakdown with quantities and rates by element, not a lump sum. A lump sum gives you nothing to compare against, which means you cannot detect an overrun until the money is gone.
How do I price a bill of quantities?
You do not price it yourself. You issue the unpriced bill to several contractors and have each of them price the same quantities. That is the other reason the document exists: it makes competing quotes genuinely comparable, because every bidder is pricing an identical measure rather than their own interpretation of the drawings.
What is the difference between a provisional sum and a contingency?
A provisional sum sits inside the contract for work that is known to be needed but not yet specified. A contingency sits outside it, in your budget, for the unforeseen. Confusing the two is how a build spends its safety margin before the ground is broken. The distinction is covered in how to budget for building your own house.
How often should the bill be compared to actual spend?
Weekly while work is active. The value of the comparison decays fast: a variance found in week six still has a cause somebody remembers and a decision still available, and the same variance found at handover has neither.