Navisworks quantity takeoff: Quantification across several models, the workbook and what I check
Navisworks quantity takeoff is what I use when a project has several models, for example architecture, structure and building services, and I want one takeoff workbook for all of them. Quantification takes the elements from the model with their properties, lets me add by hand whatever does not exist in the model, and also measures on 2D sheets. What follows is the way I work and my own experience, not a list of everything the software can do.
Navisworks quantity takeoff: when I use Quantification
Navisworks is Autodesk's software for reviewing and coordinating models, and I work with Navisworks Manage. Quantification is available to users of Navisworks Manage and Navisworks Simulate. Navisworks Freedom, the free viewer, is for viewing only and cannot save files. I open Navisworks when models from different sources have to be brought together, or when the model arrives as a Navisworks file. From a single Revit model I take quantities in Revit itself or in AiN Engine.
Quantification measures length, width, thickness, height, perimeter, area, volume, weight and count, for architecture, structure, building services and civil works such as earthworks and roads. Anyone who wants to see what else the software does will find it on Autodesk's Navisworks page.
Autodesk and Navisworks are trademarks of their owner, and this site has no connection with it.
Three ways I take off quantities
- Model takeoff. I select elements, a group or the whole selection tree, and drag them onto an item in the workbook. Quantification uses the properties saved in the source file and creates takeoff lines automatically. This works only when the properties and the unique identifier of each element were exported from the source application, and only at group level or above.
- Virtual takeoff. For items that have no element in the model, or that have a shape but no properties. I attach a viewpoint to the line so I can go back to it, and enter the quantity by a formula or with the measuring tools. Such a line is not updated from the model.
- 2D takeoff. I mark lines, areas and count points on a 2D sheet, and the result goes into the same workbook, next to the 3D takeoff. A PDF can also serve as a sheet.
The workbook, the catalogs and the export to Excel
The Quantification workbook is my workspace. On one side, the list of items and work breakdown structure codes; in the middle, a summary of each item; and below, all the takeoff lines. It can be viewed by items or by resources.
Behind the workbook there are two catalogs. In the item catalog, each item, for example a wall of a certain type, gets formulas that decide how it is calculated. The resource catalog holds the materials, equipment and tools, and an item can contain several resources. A catalog can be built in Excel from an Autodesk template and imported. At the end of the work I export the quantities to Excel, and there I map them to the items of the bill of quantities.
When the model changes: change analysis and updates
A model changes during design, and a takeoff done on an earlier version goes out of date. When a new version arrives, I run Analyze Changes: it compares the properties between versions and marks in the workbook what has changed, with bold text, a triangle in the corner of a cell, an icon in the status column and a flag next to a changed item. After the review I decide what to approve. A single line can also be updated from the current properties of the model, and a line that is no longer relevant can be deleted. Virtual takeoff lines are not updated, so I go over them by hand for every version.
Where I check by hand
Before a Navisworks quantity takeoff goes into the bill, I check:
- Duplicates between models. A slab that exists in both the architectural and the structural model is counted twice if both are taken off. I decide in advance which model each item comes from.
- Properties that were not exported. If the export from the source application did not include properties, model takeoff will not work, and only virtual takeoff is left.
- Measurement rules. The tool measures geometry. Deducting openings, overlaps and additions under the method of measurement are decisions for whoever prepares the bill.
- Catalog formulas. A wrong formula in one item repeats in all of its lines. I test every formula on one element before taking off a whole building.
- Cross-checking. The workbook totals against the drawings and against accepted ratios, as explained on the page on cross-checking quantities.
A Navisworks quantity takeoff is only as good as the models that went into it. The tool combines and sums up, but it does not complete what was never modelled, and it does not correct what was modelled twice.
When the model is a Revit model and you want to know how the software itself calculates, the behaviours I check are on the page on quantities from a Revit model. The comparison of all the tools I work with, from PDF to AiN Engine, is on the page on quantity takeoff software.
A quantity surveyor may be an engineer or a registered building technician, like Yaakov Avital. In my work as a quantity surveyor for construction projects I measure the quantities the way a contractor measures them, also from combined models. Pricing and estimates are an extra service: verbal feedback on prices together with the client, with no commitment.
Frequently asked questions
Is this a full guide to Navisworks?
No. It is what I do with Quantification and what I have learnt about it in my work as a quantity surveyor. The full capabilities of the software are on Autodesk's website.
Do I need Navisworks to take quantities off a model?
Not always. From a single Revit model I take quantities in Revit itself or in AiN Engine. I open Navisworks when several models from different sources have to go into one workbook.
Can I take off quantities in Navisworks without a model?
Yes, on 2D sheets, including PDF: you mark lines, areas and count points. But without a model there is no update from the model, and every change in the drawing means marking again.
Do the quantities from Navisworks go straight into the bill?
No. I export them to Excel, map them to items by the method of measurement, complete what is missing, and check them against the drawings.
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.