How do I do a quantity take-off from drawings?
A take-off is a list of quantities measured from the drawings and spec, in the units you buy the materials in. Work from the latest drawings, in the same order every time, deduct openings, keep a note of where each figure came from, and price it last.
Start with the right drawings and the scale
Get the latest drawings and the specification before you measure anything, and write down the revision letter of each sheet. If you are unsure which revision is current, ask in writing.
Then check the scale. Do not trust the scale in the title block alone, because a drawing printed at a different paper size will no longer match it. Measure a dimension that is written on the drawing and see whether it agrees. If it does not, use the written dimensions and treat the rest with care. Our guide on measuring a PDF drawing to scale covers this on screen.
Work in a set order
Take off in the same order every job, so nothing gets missed. A common order for a small building is:
- substructure: excavation, base or foundations, damp proof membrane
- superstructure: floor structure, walls, openings, internal partitions
- roof: structure, covering, insulation, eaves and fascias
- finishes: plasterboard, plaster, floor finish, paint, skirtings
- services: electrics, plumbing, heating, fixed by count or by length
Measure each item in the unit it is bought or priced in: metres (m) for skirting, pipe and cable, square metres (m2) for boarding, plaster, roofing and floor finishes, cubic metres (m3) for concrete and excavation, and number (nr) for doors, sockets and fittings.
Deduct openings and keep it traceable
Measure walls as if they were solid, then deduct doors and windows. Set yourself a rule for small openings and apply it every time. Deduct the opening from the finishes too, and add back any lining to the reveals.
For every line, write down where the figure came from: the drawing number, its revision, and the grid lines or room name. Something like "Drawing 02 rev B, grid A-B, north wall" is enough. When revision C arrives, you can see which lines to recheck.
Waste and pricing
Waste is a judgement call, not a fixed percentage. It depends on the material, the number of cuts and how the product is sold. Board sold in whole sheets always rounds up to a whole sheet. Keep the net quantity and the waste allowance as separate columns so you can see what you assumed.
Price last. Multiply each quantity, plus waste, by your own rate for that item, then add labour, plant, preliminaries and margin as you normally do.
Worked example: a 4 m x 3 m garden room
Take a timber garden room, 4.0 m x 3.0 m on plan to the outside of the walls, 2.4 m high, with one door of 0.9 m x 2.0 m and no windows.
- substructure: base area 4.0 x 3.0 = 12.0 m2. At 150 mm thick that is 12.0 x 0.15 = 1.8 m3 of concrete
- superstructure: perimeter 2 x (4.0 + 3.0) = 14.0 m. Gross wall area 14.0 x 2.4 = 33.6 m2. Deduct the door, 0.9 x 2.0 = 1.8 m2, to leave 31.8 m2. Door count: 1 nr
- roof: add a 0.2 m overhang all round. (4.0 + 0.4) x (3.0 + 0.4) = 14.96 m2 of flat roof on plan
- finishes: wall board 31.8 m2. A 2400 x 1200 sheet covers 2.88 m2, so 31.8 / 2.88 = 11.04, which rounds up to 12 sheets before waste
- services: counted, for example 4 nr double sockets, 2 nr lights, 1 nr consumer unit
On waste, if you decide on 10 per cent for the board, 31.8 x 1.10 = 34.98 m2, and 34.98 / 2.88 = 12.15, so order 13 sheets. The 10 per cent is only an example of a judgement, not a rule. To price it, multiply by your rate. With a made-up rate of £25 per m2 for boarding fixed and finished, 31.8 x 25 = £795.