Automated quantity takeoff: from Revit and Civil 3D to your Excel bill of quantities, with the backup

A takeoff deliverable has three parts:

1. The line items, in estimate order: code, description and unit.
2. The backup for each item: the elements measured, how many times they repeat and their dimensions, with a subtotal per row.
3. The summary, with the total for each item, which goes into the estimate or the summary of quantities on the plans.

Items follow a structure: CSI MasterFormat codes on building projects, the agency's pay item list on transportation and site work. Many clients also require their own spreadsheet format.

So the deliverable isn't an exported schedule: it's a document with an order, a measurement rule and a format. A shopping list is something else; we cover it in bill of materials from Revit and AutoCAD.

Each source delivers quantities its own way. None delivers the bill of quantities. We cover Civil 3D volumes in Civil 3D cross sections.

What gets done by hand today, for every version:

• Exporting Revit schedules, which come out as delimited text, and Civil 3D volumes.
• Mapping each element to its line item. If the model doesn't carry the item code on each element, it's done from memory.
• Writing the backup: one row per element, with count, length, width and height.
• Applying the measurement rules, such as deducting openings or converting units.
• Formatting it for the client, with their columns, headers and totals.
• Combining disciplines into one summary.

It's the most time-consuming part and the one that introduces the most errors, because every copy is a chance to get something wrong.

When the spreadsheet and the model disagree, it's almost always one of these:

• Elements with no line item, or the wrong one, left out of the total.
• Volumes counted twice, for example where beams, columns and slabs meet. In Revit, the join order decides which element gets each volume.
• Different units and rounding between the model, Excel and the estimate.
• Measurement rules that differ from the client's.
• Design changes that never reached the spreadsheet, because one tab was updated and another wasn't.

The model already does the math. What gets automated is the stretch to the spreadsheet:

• Mapping line items by rule, through a lookup table: category, type or material in the model, and its line item.
• Writing the backup for each item from the model elements, with their dimensions.
• Applying the measurement rules your firm or client uses.
• Combining Revit, Civil 3D and manual items in one Excel workbook, in the client's format.
• Comparing versions to show which items went up or down, and because of which elements.
• Checking before submitting: elements without an item, zero quantities or duplicated items.

With Dynamo, in Revit or Civil 3D, a script reads the elements, groups them by a line item parameter and writes an Excel file. It's quick to build and good for testing the lookup table.

With a plugin, the full deliverable comes out with one button: every discipline, the backup, the summary, the client's format and the comparison with the previous version.

The full comparison is in Dynamo or C# for Civil 3D and Revit.

We build custom plugins for Revit and Civil 3D. For the quantity takeoff, a typical plugin:

• Reads the models of every discipline and the Civil 3D volumes.
• Maps each element to its line item through your firm's lookup table.
• Writes the spreadsheet in your Excel format, with the backup for each item and the summary.
• Adds the manual items from a tab your team maintains.
• Compares it with the previous version and flags what changed and why.
• Reports what it couldn't measure or classify, before it reaches the estimate.

How we work:

1. Diagnosis (1 week, free): we look at your current spreadsheet and write down the rules for each item.
2. Prototype (1 to 2 weeks): we validate the logic on one of your projects.
3. Development (2 to 4 weeks): the plugin, tested on your own models.
4. Installation: an installer for the whole firm, a button on the top toolbar, a manual and documentation.
5. Support: updates with every new release of Revit and Civil 3D.

The source code belongs to your company: the plugin is yours.