Quantity takeoff for construction: what is measured and how the result is checked
A quantity takeoff turns the design into a list of works and quantities that can be checked and priced. Before anything is measured, you need to define what the numbers are for: preparing a tender, checking a budget, updating the design or ordering materials. The same drawing can serve several purposes, but not every quantity suits every use. This page explains what material is needed, how the measurement is organised and what to look for in the file you receive.
What to prepare for a quantity takeoff
The starting point is the material that already exists in the project: architectural and structural drawings, specifications, door and window schedules, an area table and a model, if there is one. You do not need a model to start working out the scope of the service. I can work from PDF drawings and DWG files, and bring in a Revit model when one is available and suitable. Before the quote, I check which chapters are needed and what level of detail the material you send can support.
It is important to include the revision date and the purpose of the design: building permit, tender or construction. A new drawing does not necessarily replace every old sheet, so I prepare a list of files and versions. If a section, a detail or a specification is missing, I record the gap and the items it affects. An organised checklist is on the page about preparing the material for a bill of quantities.
How drawings become lines you can check
- Define the scope of work. Decide which buildings, floors and chapters are included, and which areas come from consultants or stay outside the order. That way both the client and whoever prices the work understand what is covered.
- Check the basis of measurement. On a drawing, confirm the units and the scale against a known dimension; in a model, check the units, the levels and the elements that were included. Conflicting dimensions stay a question for the designer and do not turn into a silent assumption.
- Measure by item and unit. Area, length, volume and number of units are recorded according to the work and the measurement rules chosen for the project. Gross and net areas are not added together without explaining what each one includes.
- Keep an audit trail. Next to each measured result, record the building, the floor and the relevant source: a drawing, a detail or a model element. Where it fits, show the intermediate dimensions and the assumptions used in the calculation.
- Cross-check and flag anomalies. Look for duplicates, missing items and gaps between floors or between sources. A comparison with the area table or with a quantity from another chapter is a supporting check; it does not replace reading the design.
The check does not end when the Excel formula returns a number. You need to know that the dimensions refer to the same area, that the unit matches the item and that no work already counted elsewhere has been included. For example, when two chapters refer to the same element, I check whether they describe different works or a duplicate that needs clarifying.
Typical floors, flats and the building model
Splitting the quantities by floor and by flat shows where each quantity sits and lets you check it against the design. On typical floors, repetition can be relied on only after checking what is really identical: area, openings, height, finish details and the drawing revision. I mark separately the floor that was measured, the number of repetitions and the differences. The basement, the ground floor and the roof are checked against their own design.
A model, too, does not necessarily include all the works. A layer that was not modelled, a detail that appears only on a drawing or an element in the wrong category can all affect the result. What comes out of the model depends on what is in it, and anything added from another source should stay identifiable. The page on quantities from a Revit and BIM model explains what to check before using the model data.
What you receive in the file, and what is left open
The deliverable and its level of detail are agreed in the service quote. An Excel file can bring together descriptions of work, units, quantities, the split into chapters and the location in the project, with references to the source and notes. When the deliverable is meant for a tender, the measurements are organised in a bill of quantities (BOQ) with a structure that lets bidders fill in unit rates. A cost estimate and pricing are separate scopes that need their own definition; they should not be inferred from the mere existence of a quantity table.
Missing is not zero. When there is no basis for a quantity, I mark it as open and explain what is needed. If a temporary estimate has been agreed, I mark it as an estimate and state its basis. That way the reader can tell a measured figure from a figure calculated on an assumption and from a question that has not yet been resolved.
A quantity takeoff for ordering materials needs a further check of waste, packaging, delivery stages and approved selections. As an illustration only, a tiling area measured on a drawing does not by itself tell you how many boxes to order. No single waste rate fits every material and every room. The distinction is set out in the guide to physical quantity, BOQ quantity and order quantity.
How a design change is handled
When a new revision arrives, I keep the previous measurement basis and check what has changed. A useful comparison shows the previous quantity, the updated quantity, the difference and the source of the change. A change in the unit or in the item description needs a mark of its own; it is not just a change in a number. The scope and terms of the update depend on the order and on the new material.
I am Yaakov Avital, a quantity surveyor and registered building technician, and I provide quantity takeoff and BOQ preparation services for construction projects. To see whether this fits your project, tell me what is planned, which chapters you need and what material already exists. The scope, the deliverables and the timetable are set in a written quote.
Frequently asked questions
Can the work start without a model?
Yes. I can measure from PDF and DWG drawings when they give a suitable basis for measurement. If there is a model, I check what it adds and which works still need the drawings or the specification to be read.
Does a quantity takeoff include prices?
Not necessarily. The measurement deals with the quantity and its source. Adding prices, preparing a cost estimate or pricing an existing BOQ is defined separately, together with the source of the prices and the scope of the work.
Is every figure in the model ready for a tender?
No. I check what the elements include, their units and the measurement rules of the item. A geometric result may need adjusting or completing before it goes into a BOQ for pricing.
What training does the person preparing the quantities have?
A quantity surveyor can be an engineer or a registered building technician, like Yaakov Avital. Alongside the training, look at experience in the relevant work, the measurement sources and the extent of the check that was agreed. A professional degree does not replace checking the design and the quantities of the specific project.
Have a project? Tell me briefly what the project is and what already exists. When the project is a good fit, I usually reply with focused questions and a written quote.
Contact me for a quote* Created with AI for marketing, for illustration only. Not reviewed by Yaakov Avital and not professional advice. Every project must be checked on its own by a professional quantity surveyor and an engineer.