A roofing quotation is not a price — it is a list of assumptions about your building. Two quotes for the same house can differ by forty percent without either being dishonest; they simply assume different gauges, different waste and different accessory counts.
Start from the roof area, not the floor area
The covering is priced against the sloped surface, including eaves. On a typical 6/12 pitch with a 600 mm overhang, that surface runs 20–35% larger than the footprint. If every quote works from floor area, all of them are under-counting sheets.
The six cost headings
- Materials — covering, gauge, coating, underlay and waste
- Structural work — trusses, purlins and battens
- Labour — driven by pitch, height and complexity
- Accessories — ridges, valleys, flashings, gutters, fixings and sealants
- Transport — distance, road access and long sheet lengths
- Site requirements — scaffolding, occupancy, weather and disposal
The line that predicts trouble
If accessories are missing, they have not been forgiven — they have been deferred. Ridges and gutters cannot be omitted from a real roof, so they return as variation orders after the old roof is off and the crew is on site.
Ask for gauge, coating class and profile in writing. “Iron sheets, supply and fix” is not a specification; “0.5 mm pre-painted box-profile, colour both sides, manufacturer X” is.
You can estimate the roof area yourself with our calculator before comparing quotes, so you can tell a measured price from a guess.