A Bill of Quantities (BOQ) is one of the most important documents in any construction project. It tells contractors exactly what to price, gives clients clarity on what they are paying for, and gives quantity surveyors a tool to control project costs from tender to final account.
In simple terms.. a BOQ is a detailed list of every item of work required to build a structure, measured and described according to recognised standards.
This guide walks you through exactly how to prepare a BOQ for a residential building in Kenya, from understanding the structure of a BOQ to the measurement rules you must follow.
Quick Answer: To prepare a Bill of Quantities for a residential building in Kenya, measure all work items from architectural and structural drawings using standard measurement rules (AAQS or SMM7), group them by trade (substructure, superstructure, finishes, external works), price each item, and compile into a bound document for tender.
What Goes Into a Bill of Quantities?
A BOQ for a residential building typically contains the following sections, arranged by trade or work package:
- Preliminaries – general conditions, contractor obligations, and site establishment costs
- Substructure – excavation, hardcore, blinding, foundations, ground beams, and ground floor slab
- Superstructure – columns, ring beams, walls, floor slabs, and roof structure
- Finishes – plastering, screeding, tiling, painting, and ceiling works
- Doors and Windows – supply and fix, including frames and ironmongery
- Plumbing and Drainage – soil pipes, water supply, manholes, and septic tanks
- Electrical Works – wiring, conduits, switchgear, and fittings
- External Works – paving, fencing, gates, and landscaping
- Provisional Sums and Prime Cost Sums – for specialist works not yet fully designed
Each section follows a structured format: item reference, description, unit of measurement, quantity, rate, and amount.
Which Measurement Standard Should You Use?
In Kenya, the standard reference for measuring construction works is the African Association of Quantity Surveyors (AAQS) method of measurement, which aligns broadly with the Standard Method of Measurement (SMM7) used in many Commonwealth countries.
The key principle is that every item must be measured net in place. This means you measure the finished dimension, not the raw material quantity. Concrete in a beam, for example, is measured in cubic metres based on the beam’s net dimensions after formwork is in place.
For civil works like earthworks and drainage, reference is also made to the Civil Engineering Standard Method of Measurement (CESMM4).
Honestly.. if you do not understand the measurement rules for each trade, you will produce a BOQ with errors that either overprice or underprice the work. Neither is good for the client or the contractor.
Step-by-Step Process for Preparing a Residential BOQ
Here is a practical breakdown of how to produce a BOQ from scratch:
Step 1 – Collect the drawings.
You need the full set: architectural drawings (floor plans, elevations, sections) and structural drawings (foundation layout, column schedule, beam details, slab reinforcement). Without a complete drawing set, your measurements will be incomplete and your quantities will not be reliable.
Step 2 – Take off quantities.
This is the measurement phase. Go through each drawing systematically and measure each item of work. Use a dimension paper with three columns: dimension, squaring, and description. Record length x breadth x height for volumes, length x breadth for areas, and linear metres for linear items.
Step 3 – Abstract and bill.
Transfer your measurements from dimension paper into trade sections. Group similar items, add up quantities, and write them into the bill format with descriptions and units.
Step 4 – Price the bill.
At tender stage, the BOQ goes out to contractors to price. Each contractor inserts their rates for each item. The quantity surveyor then analyses the returned bills, checks for errors or unbalanced rates, and recommends a contractor to the client.
Step 5 – Check and issue.
Before issuing for tender, cross-check all quantities against the drawings. A common mistake is forgetting to deduct voids (door and window openings) from wall areas. These errors inflate quantities and mislead contractors on their pricing.
Common BOQ Units of Measurement by Trade
| Trade | Common Items | Unit |
|---|---|---|
| Excavation | Bulk excavation | m³ |
| Concrete Works | Foundation concrete, slabs | m³ |
| Masonry | Blockwork walls | m² |
| Reinforcement | Steel bars in beams/slabs | tonnes |
| Formwork | Beam sides, slab soffits | m² |
| Plastering | Internal/external walls | m² |
| Tiling | Floor and wall tiles | m² |
| Drainage | Soil pipes, drain runs | m (linear) |
| Doors/Windows | Frames and leaves | nr (number) |
Common Mistakes Quantity Surveyors Make in BOQ Preparation
The truth is.. even experienced QS practitioners make avoidable mistakes. Here are the most common ones:
- Not deducting openings. When measuring blockwork, you must deduct the area of all door and window openings. Failing to do this inflates the brick and block quantity significantly.
- Mixing up units. Reinforcement bars are priced in tonnes, not metres. Plastering is in m², not m³. Confusing units leads to wildly incorrect costs at tender stage.
- Ignoring wastage. While the BOQ measures net quantities, your pricing must account for material wastage. The standard allowance for tiles in Kenya is typically 10-15% for cuts and breakage.
- Skipping preliminaries. Preliminaries can account for 10-20% of total project cost. Leaving them out or under-pricing them creates serious financial risk for the contractor.
- Unclear descriptions. An item described simply as “concrete” is not enough. The correct description must include the mix ratio (e.g., 1:2:4 or C25/30), the location (foundation, slab, beam), and the method of placement.
Frequently Asked Questions
Q: How long does it take to prepare a BOQ for a residential building in Kenya?
For a standard 3-bedroom residential building, a competent QS can complete a BOQ in 3-7 working days, depending on drawing completeness and the complexity of finishes. Rushed BOQs with incomplete drawings almost always produce errors that return as costly variations during construction.
Q: Can I prepare a BOQ without formal QS training?
Technically yes, but the risk of error is very high. BOQ preparation requires knowledge of measurement rules, trade descriptions, and pricing principles. A poorly prepared BOQ will attract inflated bids from contractors or lead to serious budget overruns. Engage a registered QS for any project above KES 5 million in contract value.
Q: What is the difference between a BOQ and a cost estimate?
A cost estimate is a rough projection of what a project might cost, usually prepared before detailed drawings are complete. A BOQ is a detailed, measured document prepared from complete drawings, used for competitive tendering. The BOQ is far more accurate and legally forms part of the contract.
Final Thoughts
Preparing a Bill of Quantities is one of the most technically demanding tasks in the construction industry. It requires accuracy, knowledge of measurement standards, and a deep understanding of how buildings are actually built.
Get it right, and you give contractors a fair basis for pricing. Get it wrong, and you set the project up for disputes, variations, and cost overruns. The skill of a quantity surveyor is in that detail.
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