Most MEP bills of quantities go wrong in the same places: risers measured as dots on a plan, fittings forgotten, cable lengths taken “as the crow flies” and a waste factor hidden inside the numbers. A few habits make a take-off faster to produce and much easier for someone else to check.
Step by step
- Read the measurement rules before you measure. The contract or the client usually names a method of measurement or gives preambles: units, which fittings are included in the pipe rate, how supports and insulation are measured. Why: the same pipe run can be one line or six lines depending on the rules.
- Freeze the drawing set. Record the sheet numbers and revisions you are measuring from in the take-off header. Why: when a revision arrives, you can see at once which BOQ lines are affected.
- Split by system, then by zone or level. For example “Domestic cold water — Level 2” rather than one long list per discipline. Why: the client can compare zones, the site team can order per floor and errors stand out (a typical floor that is 40 % bigger than the others).
- Measure pipes and cables along the route, per size. Use the centreline on the plan, then add what the plan does not show: riser lengths from the riser diagram or sections, drops to equipment, and vertical rises at wall-mounted items. Why: a riser is only a circle on a plan, but it can be a quarter of the run.
- Count fittings and valves separately unless the rules include them. Bends, tees, reducers, isolating valves, strainers and flexible connections each get their own count per size. Why: on small-bore pipework the fittings can cost as much as the pipe.
- Measure ductwork by surface area. Rectangular duct area = 2 × (width + height) × length; group by size or gauge range as the rules require. Count dampers, grilles and diffusers, and measure insulation separately in m². Why: sheet metal is priced by area and thickness, not by running metre.
- Measure cables from board to load along the real route. Follow the tray or conduit route on the plan, add the riser height and a termination allowance at each end (into the board and up to the equipment). Why: straight-line cable lengths are always short.
- Keep quantities net; show waste separately. If your estimate needs an allowance, put it in its own column (for example 3–5 % on pipe) so a checker can see it. Why: waste hidden in quantities gets added twice — once by you and once in the rate.
- Mark what you have measured. Highlight each run on a copy of the drawing, or put measured objects on a “measured” layer, and tick off each schedule. Why: it is the only reliable way to prove nothing was missed or counted twice.
- Check against a rule of thumb. Compare totals per m² of floor area or per fixture with a similar past project. Why: a sanity check catches a dropped zero or a missing floor.
Worked example
Duct. A 600 × 400 mm duct, 25 m long: perimeter = 2 × (0.6 + 0.4) = 2.0 m, area = 2.0 × 25 = 50 m² of sheet metal; with 25 mm insulation, measure insulation as a separate 50 m² line (or as the rules define it).
Units at a glance
| Item | Usual unit | Watch out for |
|---|---|---|
| Pipes, conduits, cable trays | m per size and material | Risers, drops, offsets around beams |
| Fittings, valves, supports | nr per size | Whether the rules include them in the pipe item |
| Rectangular and round duct | m² per size or gauge range | Fittings measured as extra area or counted |
| Insulation and cladding | m² or m per size | Valves and flanges often get separate boxes |
| Cables | m per type and size | Riser height, termination allowance, route not straight line |
| Equipment, fixtures, devices | nr | Count from schedules, then cross-check on plans |
Taking quantities from a model
A BIM model schedule is a fast start, not a finished BOQ. Check that every element is modelled at a level of development that supports measurement (see BIM LOD for MEP models explained), that hidden or duplicated elements are excluded, and that supports, sleeves and small fittings — often not modelled — are added by rule. Clean layer names and system names make filtering much easier, so follow your MEP drawing layer and sheet standards. For vertical lengths, a clear riser diagram is the best source, and after MEP coordination the offsets around beams can add several per cent to pipe and duct lengths.
Typical values — verify with the edition adopted locally and with the method of measurement named in the contract.
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FAQ
How is ductwork measured in an MEP BOQ?
Usually by surface area in square metres, grouped by size or sheet thickness range: perimeter times length for each duct size. Dampers, grilles and diffusers are counted, and insulation is measured as a separate item.
Should waste be included in BOQ quantities?
Normally no. BOQ quantities are measured net, and the contractor allows for waste in the rate. If your own estimate needs a waste factor, keep it in a separate, visible column.
Why are my pipe quantities always short?
Most often because risers, drops to equipment and offsets around beams are not visible on the plan. Take vertical lengths from the riser diagram and sections and add them per size.
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