Takeoff from PDF and DWG vs from a Model

Takeoff means measuring the quantities of work from the design: cubic metres of concrete, square metres of plaster, numbers of doors, kilograms of steel. It is the first half of every estimate. The second half, pricing, comes in the next lesson.

There are two routes.

Route A: measuring from PDF or DWG

This is how most Indian houses, villas and small builder projects are measured.

1. Collect the GFC set and check every sheet's revision.
2. Check the scale. Measure a known dimension on the sheet and compare it with the figure written on it.
3. Measure item by item in length x breadth x depth, following IS 1200, the Indian standard method of measuring building work. It sets units and rules for each trade, such as what to deduct for openings.
4. Write a measurement sheet that shows every calculation, so anyone can check it.
5. Abstract the measurements into BOQ items.

Tools: a scale and calculator; Excel; on-screen PDF measurement in tools like Bluebeam Revu or PlanSwift; measuring directly in AutoCAD from the .dwg.

Strength: transparent. Every number can be traced to a drawing and a calculation. Limit: slow, and it depends on the person's care.

Route B: from a BIM model

If a clean model exists, its schedules can give counts, areas and volumes directly.

1. Check the model: are walls, slabs and beams the right types? Do joins deduct overlaps? Are levels right?
2. Export schedules from the BIM tool, or use a takeoff tool that reads the model. Examples include CostX (now sold as RIB CostX) and Navisworks quantification.
3. Map model quantities to BOQ item descriptions.

Strength: fast, and quick to update after a design change. Limit: it needs a model built for quantities. Many Indian projects do not have one.

A worked example: two common errors

Error 1: PDF scale. A plan drawn at 1:100 on A1 is printed on A3, which is half the size in each direction. A 4.20 m wall now measures 21 mm on paper. Read at 1:100, that is 2.10 m. Half the true length. Always check a known dimension first.

Error 2: double counting in a model. A first-floor slab and its beams were modelled as separate elements without cleaning up the joins. The model schedule says 58.4 m³ of concrete. A careful manual takeoff, counting each beam only below the slab, gives 54.9 m³. The difference is 3.5 m³. At ₹8,500 per m³ of RCC (illustrative), that is ₹29,750 of concrete that does not exist, on one floor.

Which route to use

Whatever the route, the final step is the same: check the quantities against the drawings. A quick benchmark also helps. For example, RCC in a typical framed house often falls within a known range per square metre of built-up area. A figure far outside that range is a reason to recheck, not proof of an error.

What comes next

Quantities alone do not make a budget. Next, we price them using SOR rates and rate analysis.