Roofing Calculator
Sheet area and cost for a metal roof.
Estimate the roof sheeting area and cost from the building's plan area and roof pitch, using SA IBR / Chromadek benchmark rates.
- Roof (sloped) areaplan area × pitch factor126.0 m²
- Sheeting to order138.6 m²+10% overlaps & offcuts
- Estimated installed costR 335/m² (incl. structure)R 46 431
Pitch factor converts plan area to sloped area. Installed-cost rate from NNAQS benchmark data (sheeting incl. supporting structure). Purlins, flashings, and insulation vary by detail.
Questions
- How do I convert plan area to roof area?
- Multiply the footprint by a pitch factor: ~1.0 for flat, ~1.05 for moderate pitch, ~1.15 for steep. A steeper roof has more surface area for the same footprint.
- Is IBR or corrugated cheaper?
- IBR and corrugated Zincalume are similar in price per m². Chromadek and insulated panels cost more but include a colour finish and thermal performance.
- What does the installed cost include?
- Sheeting plus the supporting timber or steel structure. Flashings, ridge caps, insulation, and gutters are detailed separately on a real BoQ.
Compiled by Setout. Figures are planning-stage estimates, not quotes.