LoadingLoadingLoadingLoadingPick a slate size or enter your own, set the headlap, and get the batten gauge, slates per square metre, the order quantity and an indicative delivery weight for the scaffold and the wagon.
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100 mm headlap suits most UK roofs at 30° and above; increase it for lower pitches and exposed sites. 500 × 250 mm at a 100 mm lap works out at 20 slates per m² — the classic figure.
Batten gauge
200 mm
(Slate length − headlap) ÷ 2 — the spacing between batten centres.
Slates per m²
20,0
Slates to order
1260
Delivery weight
2,17 t
Order quantity × weight per slate at 2,750 kg/m³ nominal density — natural slate varies by quarry.
Roof load
34 kg/m²
Estimates only. Headlap requirements depend on pitch and exposure (see BS 5534), and weight varies with quarry and thickness. Confirm with your supplier — and check the roof structure can carry the load.
Slating is double-lap: every part of the roof carries at least two thicknesses of slate, and the batten gauge — (length − headlap) ÷ 2 — sets how many you need. Get the lap wrong and the count is wrong across the whole roof.
Weight matters as much as count. Natural slate runs around 25–35 kg per square metre on the roof, and several tonnes arrive on the wagon for an average re-roof. The structure, the scaffold loading bay and the delivery plan all need that number before the slates do.
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