Pitch is not a style choice. Every covering has a minimum below which water finds its way under it, and that minimum is why a low extension roof costs more per square metre than the main house does.
What it costs you
Every rate on this page is an install rate before tear off, complexity, scaffolding, waste and contingency. Put it through the estimator to see what a whole job in this material costs.
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Plain clay tile
Cheap per square metre and heavy. A roof that has carried concrete for forty years may need its timbers checked before clay goes back on, and that check is in nobody’s rate per square metre.
Min pitch
35 deg
Typical
40 deg
Rate / m2
58
Service life
60 yr
Weight
45 kg
Natural slate
The dearest rate on this list and the only hundred-year one. Priced per year of roof it is the cheapest thing here, which is the arithmetic a quote never shows you.
Min pitch
25 deg
Typical
30 deg
Rate / m2
96
Service life
100 yr
Weight
35 kg
Concrete interlocking
The default, and the heaviest. Large format means fewer units and faster laying, so the labour line falls even though the material line does not.
Min pitch
18 deg
Typical
25 deg
Rate / m2
42
Service life
50 yr
Weight
48 kg
Standing seam zinc
Goes down to five degrees, which is why it turns up over extensions where nothing else works. Almost all of the price is labour, so a complexity uplift bites harder here than anywhere else on this list.
Min pitch
5 deg
Typical
15 deg
Rate / m2
132
Service life
80 yr
Weight
12 kg
EPDM single ply
A flat roof is the one case where footprint and roof area are the same number, so every square metre you measure is a square metre you pay for.
Min pitch
1 deg
Typical
2 deg
Rate / m2
68
Service life
30 yr
Weight
5 kg