Quantity take-off: from the drawings to the bill of quantities
Quantity take-off is working out the quantity of each work item from the drawings and specification in its unit of measurement, such as cubic metres of concrete, square metres of masonry or tonnes of reinforcing steel. Measurements are recorded in a measurement sheet showing the count and dimensions for each item, then totalled in the bill of quantities, which is priced and becomes the basis of the tender, the budget and the payment certificates.
By Ta3mir engineering team · Published · Last updated
Kinds of take-off and what they produce
| Take-off for pricing | Take-off for a certificate | |
|---|---|---|
| Source | Drawings and specification, before construction | Work actually done on site |
| Purpose | Prepare the bill of quantities, price the tender and set the budget | Prove the quantities done in each certificate |
| Prepared by | The contractor's technical office or the consultant | The site engineer, checked by the consultant |
| Output | A measurement sheet and a bill of quantities | A measurement sheet for the period, attached to the certificate |
Either way, every figure in the bill must trace back to a line in the measurement sheet, and every line to a drawing and a location. That is what makes a quantity checkable at approval or in a dispute.
How a bill of quantities is laid out
| Column | What it holds |
|---|---|
| Item no. | Numbered by work section, such as earthworks, then concrete, then masonry, then finishes |
| Description | The work, materials and specification it covers; the rate covers everything the description says |
| Unit | The agreed unit of measurement for the item |
| Quantity | The net figure from the measurement sheet |
| Unit rate | The rate from the rate analysis |
| Amount | Quantity × unit rate, then section totals and the grand total |
In remeasurement contracts the bill quantities are estimates, and the contractor is paid for the quantities actually measured (sub-clauses 1.1 and 12.3 of the FIDIC Red Book 2017). The method of measurement is the one in the Contract Data or consistent with the bill, measuring the net actual quantity of each item with no allowance for bulking or waste unless the contract says otherwise (sub-clause 12.2).
Common units of measurement
| Work | Common unit |
|---|---|
| Excavation and backfill | Cubic metre (m³) |
| Plain and reinforced concrete | Cubic metre (m³) |
| Reinforcing steel | Tonne or kilogram |
| Masonry | Square metre (m²), or cubic metre per the contract |
| Waterproofing, plaster, paint and tiles | Square metre (m²) |
| Skirting, pipes and cables | Linear metre (m) |
| Doors, windows and sanitary fittings | Number, or square metre for windows per the contract |
These are common units in practice. The binding unit is the one written against the item in your contract's bill of quantities, so do not change it when measuring.
The order and rules of measurement
- Start from the list of items in the specification so none is missed, then measure in construction order: earthworks, blinding, foundations, waterproofing, backfill, columns and slabs, masonry, finishes, then electromechanical work.
- Use the dimensions written on the drawing; do not scale off a printed drawing.
- Record each measurement on its own line: location or grid line, count, length, width and height.
- Follow a fixed direction on each plan, such as clockwise from a given grid line, so no element is counted twice or missed.
- Deduct openings from masonry and finishes as the contract's method of measurement says.
- Total the measurement sheet for each item and carry the net figure to the bill in the same unit.
Common take-off errors
- Double counting at intersections, such as measuring column concrete inside a beam or slab twice.
- Forgetting to deduct openings from masonry, plaster and paint, or deducting small openings the method of measurement excludes.
- Adding a waste allowance to the bill quantity; where measurement is net, waste belongs in the unit rate analysis.
- Mixing units, such as measuring masonry in square metres and pricing it per cubic metre.
- Measuring from an unapproved or superseded drawing without recording its number and revision.
- An item in the description with no line in the measurement sheet, or a line with no location to check.
Worked example: a measurement sheet and four priced items
Illustrative dimensions and rates. A small building with 6 isolated footings under 6 columns, and brick walls 40 m long and 3.00 m high, with 2 doors (1.00 × 2.20) and 4 windows (1.50 × 1.20).
| Item | Count × dimensions (m) | Quantity | Unit rate (EGP) | Amount (EGP) |
|---|---|---|---|---|
| Plain concrete blinding under footings | 6 × 2.20 × 2.20 × 0.10 | 2.904 m³ | 1,800 | 5,227.2 |
| Reinforced concrete footings | 6 × 2.00 × 2.00 × 0.50 | 12 m³ | 4,500 | 54,000 |
| Reinforced concrete columns | 6 × 0.30 × 0.60 × 3.00 | 3.24 m³ | 5,200 | 16,848 |
| Brick walls less openings | 40.00 × 3.00 − 11.60 | 108.4 m² | 450 | 48,780 |
| Total | 124,855.2 |
The gross wall area is 120 m² and the openings 11.6 m² (4.4 for doors and 7.2 for windows), so the net is 108.4 m². Note that reinforcing steel is not in this example: it is measured as its own item in tonnes from the reinforcement details, or included in the reinforced concrete rate if the item description says so.
Steps for a quantity take-off
- Gather the latest approved drawings, the specification and the contract's method of measurement.
- List the items and their units before you start, grouped by work section.
- Measure in construction order on a measurement sheet: one line per measurement, with its location and dimensions.
- Deduct openings and check intersections so no element is counted twice.
- Carry each item's net quantity to the bill and price it from the rate analysis.
- Have another engineer check the take-off before the bill is approved, then freeze the approved version.
How to do it in Ta3mir
In Ta3mir you do the take-off, the measurement sheets and the project bill of quantities in one place, with totals summed automatically.
- Measurement sheets with length, width and height per measurement, for a documented quantity checked item by item.
- Eight take-off calculators for footings, columns, slabs, rebar, brick, plaster, paint and tiles, with results pushed into the bill.
- Several bills per project with their status; approval freezes quantities and rates as the project budget base.
- Import a bill from Excel and review it before saving, and export it to Excel, CSV or PDF.
Sources
This guide is an explanatory summary written by the Ta3mir engineering team and is not the text of any contract or specification. Dimensions and rates in the example are illustrative. The method of measurement and item units in your contract and its bill of quantities govern.