Roofers price in rates per square metre because it is the only way to quote work whose area varies. Owners then compare rates between quotes and conclude that the dearer one is overcharging, which is usually wrong: the rates differ because they cover different things, and the only way to compare them is to find out what each one includes.
What a square metre rate normally includes
Stripping the existing covering and getting it into the skip. New treated battens at the gauge the covering requires. A breathable underlay across the whole slope. The covering itself, mechanically fixed to the pattern that the site's exposure demands. What it usually does not include is the scaffold, the skips, the ridge and verge systems, any leadwork, and anything found once the covering is off. Those are separate lines, and a quote showing only a rate has not shown you them.
Why labour and materials split unevenly
On a concrete interlocking tile roof the covering is cheap and the labour is quick, so the rate is low and the fixed costs of scaffold and waste are a large share of the total. On a natural slate roof the material is expensive and the labour is slow, so the rate is high and the fixed costs matter less. That is why two quotes with very different rates per square metre can end up close on total price, and why the total is the number to compare.
Turning a rate into your price
Measure the footprint of each roof plane, work out the sloped area from the pitch, and add the two together for a gable roof or four for a hip. Multiply by the rate. Then add scaffold by the week, skips by the number, ridge and verge by the linear metre, and a provisional sum for timber. What you have is not a quote, but it is a number that will tell you which of three quotes has quietly left something out.
Questions people ask about roofing cost per m2
Is a low rate per square metre a good sign?
Only if it covers the same work. The commonest reason for a low rate is that the scaffold, the waste, the ridge system or the underlay upgrade are priced separately or not at all.
How do I work out my roof area?
From the footprint of each plane and the pitch. The sloped area is always larger than the plan area, and using the plan area is the mistake that makes owners think every quote is high.
Do roofers charge a day rate instead?
For repairs, commonly yes, because the work is not measurable in advance. For a re-roof, a rate per square metre plus itemised fixed costs is the norm and the more comparable format.