Roofing Takeoff
Roofing is one of the most shape-dependent takeoffs in construction. Roof geometry is complex, BIM models often simplify or approximate it, and the quantities needed for ordering — membrane area, insulation layers, drainage linear metres — rarely map directly to model elements. Sparkel handles this through a combination of shapes and BIM linking that gives you accurate, orderable quantities regardless of model quality.
What you're typically measuring
Roof membrane area — m², split by roof zone or product type
Insulation — m², split by layer and thickness
Vapour barrier — m²
Drainage channels and gutters — m
Flashings, upstands, and edge trims — m
Roof penetrations — pcs
Ballast or pavers — m² or tonnes
Step 1: Start with the BIM model for overall geometry
Open the model in the viewer and isolate roof elements. Use IfcRoof or IfcSlab elements classified as roof to get a starting area figure. This gives you a baseline to cross-check your shape measurements against. See BIM Linking for how to filter and link elements by IFC class.
Step 2: Use shapes for precise zone measurement
For roofing procurement, shapes are almost always the right tool. Draw polygons over each roof zone — flat areas, sloped sections, plant room surrounds — and name them clearly. Each shape gives you an immediate area reading in the table.
This is particularly powerful for complex roofs where multiple membrane products meet at different zones, or where a supplier needs quantities split by drainage direction or fall gradient.
Step 3: Add linear measurements for drainage and trims
Use line shapes to measure drainage channels, gutters, and flashings. Draw along the relevant edges in the model or on the PDF roof plan. Sparkel calculates the length automatically and adds it to the table. See Shapes for details on the different shape types available.
Step 4: Work from PDF if the BIM model is insufficient
Roofing contractors frequently find that the architectural IFC model doesn't contain enough roof detail to measure accurately from. In this case, upload the roof plan PDF, set the drawing scale, and draw shapes directly on the 2D plan. The workflow is identical to 3D — shapes appear in the quantity table as soon as you draw them.
Step 5: Send to the roofing supplier
Roofing suppliers typically quote per zone and product type. Structure your takeoff items to match your supplier's quoting structure — this makes the comparison of quotes straightforward. Then add the supplier in Sparkel, publish the takeoff, and communicate through the platform thread to keep everything in one place.