Roofing Quantities: Estimation Basics
Pitched and flat roofing takeoff notes: areas, laps, insulation, and how BOQ lines often split supply and fix.
What to measure
Measure roof plan areas by slope or project to flat equivalents per your method. Include verge, eaves, and valley lengths where priced separately.
Membrane and insulation often have minimum laps and build-ups—tie descriptions to manufacturer details.
Pitched roofs need slope correction: plan area × pitch factor unless your BOQ explicitly asks for plan quantities only.
Pitched vs flat systems
Tiles/slates are often counted with waste percentages; standing seam metal may be linear metres plus accessories.
Flat roofs separate insulation, vapour control, waterproofing, and ballast—each may be a different unit and supplier package.
Edges, penetrations, and safety
Ridges, hips, abutments, and penetrations drive accessory quantities—flashings and sealant are easy to undercount.
Edge protection, nets, and access for roof work may live in prelims—confirm before you bury them in m² rates.