How to Prepare a Bill of Quantities (BOQ) for a Building Project in Kenya
If you have ever watched a contractor and a client argue over payment on site, chances are the disagreement traces back to one document: the Bill of Quantities. A BOQ is what turns a set of drawings into a priceable, measurable, and payable project. Without one, tendering becomes guesswork and valuation becomes a fight.
In simple terms, a Bill of Quantities is an itemised list of all the materials, labour, and works needed to complete a project, measured according to a recognised standard method of measurement. In this guide, you will learn how quantity surveyors actually build one, from taking off quantities to structuring items that survive tendering and site valuation.
Quick Answer: A Bill of Quantities is prepared by measuring quantities directly from architectural and structural drawings using a standard method of measurement, then grouping those quantities into coded, priceable items covering preliminaries, substructure, superstructure, finishes, and services.
What a Bill of Quantities Actually Does on a Project
The truth is, a BOQ is not paperwork for its own sake. It is the pricing document every contractor uses to submit a competitive, comparable tender. It is also the valuation document the quantity surveyor uses every month to certify how much work has actually been done on site.
A well-prepared BOQ protects three parties at once. The client gets cost certainty before construction starts. The contractor gets a fair basis for pricing and claiming variations. The consultant gets a defensible record when disputes come up. Miss this step, or rush it, and every one of those protections weakens.
How to Measure Quantities Correctly
Quantity surveyors in Kenya typically measure using the Principles of Measurement (International), commonly referenced alongside the RICS Standard Method of Measurement, and cross-checked against the Kenya Building Code for construction practice requirements. The steps below reflect how this is done on a real residential or commercial building project.
- Study the drawings first. Read architectural, structural, and where available, MEP drawings together before touching a single measurement. Confirm they are the latest issued revision.
- Take off quantities systematically. Work in one direction through the building, trade by trade: excavation, concrete, blockwork, roofing, finishes, then services. Never jump around.
- Apply the correct unit of measurement. Concrete and earthworks are measured in cubic metres (m3), walling and finishes in square metres (m2), reinforcement in kilogrammes or tonnes, and items like doors and manholes as numbers (No).
- Deduct openings and voids. Doors, windows, and service ducts are deducted from wall and slab areas above the threshold set by the method of measurement you are using.
- Group into billable items. Convert raw dimensions into described, coded items ready for pricing.
How to Structure and Code BOQ Items
A BOQ is normally organised into standard sections called elements or trades. Here is a simplified structure used on most Kenyan building projects.
| Section | Typical Items | Unit of Measurement |
|---|---|---|
| Preliminaries | Site mobilisation, insurance, site office | Sum |
| Substructure | Excavation, hardcore, foundation concrete | m3, m2 |
| Superstructure | Columns, beams, slabs, blockwork | m3, m2, kg |
| Roofing | Trusses, covering, gutters | m2, LM |
| Finishes | Plaster, tiling, paint, ceilings | m2 |
| Services | Electrical, plumbing, drainage | No, LM, Sum |
Each item carries a reference number, a full description written to Standard Method of Measurement rules, a unit, a quantity, and a blank column for the contractor’s rate. Honestly, the quality of your item description is what determines whether you get comparable tenders or confusing ones. A vague description like “concrete works” invites every contractor to price it differently.
Common Mistakes That Cost Contractors During Tendering
These errors show up again and again on Kenyan sites, and they cost real money when they are missed:
- Omitting provisional sums for items that cannot be fully designed at tender stage, such as ground conditions or MEP final layouts.
- Failing to separate labour-only items from supply-and-fix items, which distorts valuation later.
- Copying quantities from a previous project instead of measuring the actual drawings.
- Not cross-checking structural and architectural drawings, which causes quantity mismatches on slabs and openings.
From BOQ to Valuation: How Quantities Follow the Project
Once construction starts, the same BOQ becomes the basis for interim valuations and, eventually, the final account. The quantity surveyor measures work actually completed on site each month and compares it against the billed quantities to certify payment.
Variations, whether from a design change or a site condition nobody anticipated, are measured and priced using the same rates and rules established in the original BOQ. That means a BOQ built with rushed or vague descriptions will keep causing valuation disputes for the entire duration of the project. Get it right at tender stage, and the rest of the project runs on a document everyone trusts.
Frequently Asked Questions
Q: What is the difference between a Bill of Quantities and a Bill of Materials?
A Bill of Quantities covers measured work items priced by a contractor during tendering, including labour, materials, and overheads combined into rates. A Bill of Materials only lists raw materials and quantities needed, without pricing structure for labour or profit.
Q: Who is responsible for preparing the BOQ?
A registered quantity surveyor prepares the BOQ, working from architectural and structural drawings issued by the design team. On smaller projects in Kenya, this task sometimes falls to a contractor’s in-house QS, but accuracy still depends on following a recognised method of measurement.
Q: Can a BOQ change after tendering?
Yes. Design changes, site conditions, and client-instructed variations are common, and they are priced using the rates already submitted in the tender. This is why accurate original rates matter so much, they set the standard for every variation that follows.
Conclusion
A Bill of Quantities is only as good as the measurement and description behind every item in it. Learn the standard method of measurement properly, measure directly from current drawings, and write descriptions a contractor can price with confidence. That discipline is what separates a BOQ that protects your project from one that causes disputes for months.
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