Every bill of quantities starts with one skill.. taking off. If you cannot measure reinforced concrete work accurately from drawings, every estimate, tender and valuation you produce afterwards is built on a shaky foundation. In this guide, you will learn how to take off quantities for reinforced concrete step by step.. concrete volumes, formwork areas and reinforcement weights.. using the measurement rules that apply on real projects in Kenya and across the region.
In simple terms, taking off means reading the structural drawings, breaking each element into measurable items, and recording dimensions in a structured way so they can be priced. The truth is.. this skill separates a quantity surveyor who is trusted with tenders from one who is only trusted with filing.
Quick Answer: To take off quantities for reinforced concrete, measure concrete in cubic metres (m3) from structural drawings, formwork in square metres (m2) of contact surface, and reinforcement in kilograms or tonnes from bar bending schedules, following a standard method of measurement such as the SMM for East Africa or NRM2.
What Taking Off Quantities Actually Means
Taking off is the process of extracting measurements from drawings and converting them into measurable units that can be priced in a bill of quantities. For reinforced concrete, that means three separate trades hiding inside one element: the concrete itself, the formwork that shapes it, and the steel reinforcement inside it.
Each one is measured differently. Concrete is measured by volume in m3. Formwork is measured by the area of surface in contact with the concrete, in m2. Reinforcement is measured by weight, in kg or tonnes, calculated from the bar bending schedule.
So a single 230 x 450 mm beam appears three times in your dimension paper.. once as concrete, once as formwork, once as rebar. Miss one and you have underpriced the element by a third or more. This is why site engineers should also understand taking off, because every variation and every interim valuation on site is measured using exactly the same logic.
The Step-by-Step Taking Off Process
Honestly, the process is the same whether you are measuring a single column base or a ten-storey frame. Follow these steps in order:
- Study the drawings first. Read the structural layout, sections and details together with the architectural drawings. Note concrete grades (for example C25/30), cover requirements and member sizes before you measure anything.
- Prepare your dimension paper. Use the standard four-column format.. timesing, dimension, squaring and description. Whether you work on paper or in Excel, keep this structure. It is your audit trail.
- Measure in a logical sequence. Work from the ground up: foundations, columns, beams, slabs, staircases. Within each element, take concrete first, then formwork, then reinforcement.
- Measure net, as fixed in position. Take dimensions from the drawings without adding waste. Waste is priced by the contractor in the rates, not added by the QS in the quantities.
- Deduct openings consistently. For slabs, deduct voids larger than the threshold your method of measurement states.. under the East Africa SMM, small openings below the stated minimum are typically ignored.
- Square and check. Multiply out your dimensions, total each item, and have a colleague spot-check at least the largest items. On a frame contract, concrete and rebar usually carry the most money.
For example, a column 300 x 300 mm and 3.0 m high gives you 0.27 m3 of concrete, 3.6 m2 of formwork (four faces of 0.3 m x 3.0 m), and whatever the bar bending schedule shows.. commonly in the range of 150 to 220 kg of steel per m3 of concrete for columns.
Measurement Rules and Units You Must Follow
Quantities only mean something when everyone measures the same way. That is why standard methods of measurement exist.. the SMM for East Africa, NRM2 in the UK tradition, and CESMM4 for civil engineering works. Tenders in Kenya commonly follow the East Africa SMM for buildings, so learn it properly.
The core rules for reinforced concrete are summarised below:
| Item | Unit | How it is measured |
|---|---|---|
| Concrete in foundations, columns, beams, slabs | m3 | Net volume as shown on drawings, stating grade (e.g. C25/30) |
| Formwork | m2 | Area of surface in contact with concrete, by location (sides of columns, soffits of slabs) |
| Reinforcement | kg or tonne | From bar bending schedule, by bar diameter, using 7,850 kg/m3 steel density |
| Blinding under foundations | m2 or m3 | Stated thickness, measured under the foundation footprint |
Two practical notes. First, laps, hooks and bends in reinforcement are calculated in the bar bending schedule, not added as a percentage guess.. although estimators often sense-check rebar at roughly 100 to 120 kg/m3 for slabs. Second, formwork to slab soffits is measured separately from formwork to beam sides because the labour and propping costs are different.
Common Taking Off Mistakes That Cost Money
The truth is.. most taking off errors are not calculation errors. They are reading errors and omission errors.
The most common one is measuring concrete through intersections twice. Where a beam frames into a column, the column is measured full height and the beam is measured between column faces.. not through them. Double-counting that junction on every floor of a building adds phantom concrete worth real money.
Another frequent mistake is taking slab thickness from the architectural drawings instead of the structural drawings. Architects show finished levels; the structural drawing governs the concrete dimension. A 25 mm difference across a 500 m2 slab is 12.5 m3 of concrete.. at current Nairobi ready-mix prices, that is a six-figure error in Kenya shillings.
Finally, many juniors forget item coverage.. what the description must state for the rate to be complete. Under the SMM, your concrete description should state the grade, the element, and whether it is poured against earth or formwork. Vague descriptions produce disputed valuations later.
Frequently Asked Questions
Q: What units are used when taking off reinforced concrete quantities?
Concrete is measured in cubic metres (m3), formwork in square metres (m2) of contact surface, and reinforcement in kilograms or tonnes. These units come from the standard method of measurement used on the project, such as the East Africa SMM or NRM2.
Q: How do I estimate reinforcement if there is no bar bending schedule?
Use typical steel ratios as a preliminary check only.. around 80 to 120 kg/m3 for slabs, 100 to 150 kg/m3 for beams, and 150 to 220 kg/m3 for columns. For tender and payment purposes, always quantify from a proper bar bending schedule.
Q: Is taking off still relevant now that software can measure drawings?
Yes. Software like PlanSwift or CostX speeds up measurement, but the measurement rules, item descriptions and judgement still come from the QS. If you cannot take off manually, you cannot check what the software gives you.
Conclusion
Taking off reinforced concrete comes down to discipline.. measure concrete in m3, formwork in m2, reinforcement by weight, follow your method of measurement, and keep a clean audit trail on your dimension paper. Master this on small elements like column bases, then scale up to full frames. Whether you are a QS preparing a tender or a site engineer checking a valuation, accurate quantities protect both the project and your reputation.
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