Navisworks Quantification: Model-Based Quantity Takeoff and Cost Estimation

Navisworks Quantification: Model-Based Quantity Takeoff and Cost Estimation

Navisworks Quantification extracts material quantities directly from BIM models and links them to cost resources for estimation. Unlike manual takeoff from 2D drawings, model-based quantification is automatic, accurate, and updates when the model changes. This guide covers the complete quantification workflow.

Setting Up Quantification

Opening Quantification

1. Home > Quantification
2. The Quantification panel opens with:
   • Item Catalog: Hierarchical list of quantity items
   • Resource Catalog: Cost resources (labor, material, equipment)
   • Takeoff: Extracted quantities from the model
   • Workbook: Cost summary by item and resource

Model Element Mapping

Before extracting quantities, map model elements to quantity categories:

1. Quantification > Model Mapping
2. For each element type (wall, slab, column, etc.):
   • Map to a quantity item in the Item Catalog
   • Specify which properties to extract (length, area, volume, count)
3. Example mapping:
   • IfcWall → "Concrete Walls" item → extract Volume
   • IfcSlab → "Concrete Slabs" item → extract Volume
   • IfcColumn → "Concrete Columns" item → extract Volume + Count
   • IfcDoor → "Doors" item → extract Count

Item Catalog Setup

Creating the Item Catalog

1. Quantification > Item Catalog > New

2. Create a hierarchical structure:

   Project
   ├── Substructure
   │   ├── Excavation
   │   ├── Foundations
   │   └── Basement Walls
   ├── Superstructure
   │   ├── Concrete Walls
   │   ├── Concrete Slabs
   │   ├── Concrete Columns
   │   ├── Concrete Beams
   │   └── Steel Elements
   ├── Envelope
   │   ├── Exterior Walls
   │   ├── Windows
   │   ├── Doors
   │   └── Roof
   ├── Interior
   │   ├── Partition Walls
   │   ├── Floor Finishes
   │   ├── Ceiling
   │   └── Paint
   └── MEP
       ├── HVAC
       ├── Plumbing
       └── Electrical
   

3. For each item, set:

   • Unit: m³, m², m, ea (each)
   • Formula: How to calculate from model properties
   • Description: Item description for the estimate

Importing a Catalog

1. Quantification > Item Catalog > Import
2. Import from:
   • CSV: Custom catalog
   • RSMeans: Standard cost data (if available)
   • Company standard: Reusable catalog from previous projects

Resource Catalog Setup

Creating Resources

1. Quantification > Resource Catalog > New
2. Create cost resources:
   • Material resources: Concrete ($150/m³), Steel ($2,500/ton), Brick ($0.50/ea)
   • Labor resources: Carpenter ($45/hr), Mason ($55/hr), Laborer ($35/hr)
   • Equipment resources: Crane ($200/hr), Mixer ($75/hr)

Assigning Resources to Items

1. Select an item in the Item Catalog
2. Click "Assign Resource"
3. Choose resource(s) and set quantity per unit:
   • Example: "Concrete Walls" (m³) → Concrete (1 m³ per m³) + Labor (2 hrs per m³) + Equipment (0.5 hrs per m³)
4. The cost per unit is calculated automatically

Running the Takeoff

Automatic Takeoff

1. Quantification > Takeoff > Auto Takeoff
2. Navisworks scans the model and extracts quantities based on the mapping:
   • Counts each element type
   • Calculates length, area, volume from geometry
   • Assigns to the corresponding Item Catalog entry
3. Results appear in the Takeoff tab

Manual Takeoff

For elements not captured by automatic mapping:

1. Select elements in the 3D view
2. Quantification > Takeoff > Add to Item
3. Select the Item Catalog entry
4. The quantity is added manually

Virtual Takeoff (For Missing Elements)

For elements not in the model (e.g., formwork, finishes not modeled):

1. Select the parent item (e.g., "Concrete Walls")
2. Click "Add Virtual Item"
3. Enter the quantity manually (e.g., formwork area = 2 × wall height × wall length)
4. Virtual items appear in the takeoff with a "virtual" flag

Reviewing Quantities

Takeoff Tab

1. Quantification > Takeoff
2. View extracted quantities:
   • Item: Catalog item name
   • Quantity: Extracted amount
   • Unit: m³, m², m, ea
   • Source: Model (automatic) or Manual
   • Elements: Number of model elements contributing
3. Sort by item, quantity, or source
4. Filter by building section, floor, or discipline

Verifying Quantities

1. Select an item in the Takeoff tab
2. The corresponding model elements are highlighted in 3D
3. Verify:
   • All expected elements are included
   • Quantities match manual spot checks
   • No duplicate elements
4. If quantities are wrong:
   • Check the Model Mapping settings
   • Verify element properties in the source model
   • Adjust the formula if needed

Workbook (Cost Summary)

Viewing the Workbook

1. Quantification > Workbook
2. The workbook shows:
   • Item: Catalog item
   • Quantity: Total quantity
   • Unit: Unit of measure
   • Resources: Assigned resources with costs
   • Total Cost: Quantity × Cost per unit
   • Subtotal: By category (Substructure, Superstructure, etc.)
   • Grand Total: Total project cost

Cost Breakdown

The workbook provides multiple cost views:

• By category: Substructure, Superstructure, Envelope, Interior, MEP
• By resource type: Material, Labor, Equipment
• By floor: Cost per building level
• By discipline: Architectural, Structural, MEP

Export

Excel Export

1. Quantification > Export > Excel
2. The workbook is exported with:
   • All items, quantities, and costs
   • Category subtotals
   • Grand total
3. Use Excel for further analysis, reporting, or integration with estimating software

CSV Export

1. Quantification > Export > CSV
2. Raw data export for import into other systems
3. Suitable for ERP or cost database integration

PDF Report

1. Quantification > Export > PDF
2. Formatted report with:
   • Project summary
   • Cost breakdown by category
   • Detailed item list
   • Resource summary
3. Suitable for client presentations

Updating Quantities After Model Changes

1. When the BIM model is updated:
2. Quantification > Takeoff > Refresh
3. Navisworks re-extracts quantities from the updated model
4. Items linked to model elements update automatically
5. Manual and virtual items remain unchanged
6. The workbook recalculates costs
7. Compare before/after to see cost impact of design changes

Best Practices

1. Set up mapping before the model is complete — start with a few element types and expand
2. Use standard catalogs — company-specific or industry-standard (RSMeans)
3. Verify with manual spot checks — compare model quantities with manual calculations for 5-10 items
4. Include virtual items for unmodeled elements — formwork, finishes, temporary works
5. Update regularly — refresh quantities after each model revision
6. Track cost changes — compare workbook versions to show cost impact of design decisions
7. Export to Excel for reporting — Navisworks is for extraction; Excel is for analysis
8. Coordinate with estimators — ensure the catalog structure matches the estimating workflow

Conclusion

Navisworks Quantification provides a direct path from BIM model to cost estimate. By mapping model elements to quantity items, setting up cost resources, running automatic takeoff, and exporting to Excel, you can produce model-based estimates that are more accurate and faster than manual 2D takeoff. The ability to refresh quantities when the model changes enables real-time cost feedback during design — a powerful tool for value engineering and budget control. By following this workflow, estimators and project managers can leverage the BIM model for data-driven cost decisions throughout the project lifecycle.