Natural slate covering costs area times the installed allowance plus confirmed extras and tax; the default example is about £20,500.
Coverage comes from headlap, not just slate size
Double-lap slating covers part of each slate with the courses above it. The exposed course height, or batten gauge, is the slate length minus the headlap, divided by two. Slates per square metre are one million divided by gauge in millimetres times slate width in millimetres. Multiply that coverage by the roof area and round up to a whole slate to obtain the net field count.
The CUPA batten-gauge formula supplies this geometry. Its headlap tables also show why pitch, driving-rain exposure and slate dimensions matter. The default 500 × 250 mm slate with 100 mm headlap matches a severe-exposure table entry at 30°. The calculator does not choose the safe headlap for your site. Have the supplier confirm the specification, then enter it.
Worked example: 80 m² of natural slate
With those dimensions, (500 − 100) ÷ 2 gives a 200 mm gauge. One million ÷ (200 × 250) gives 20 slates/m², so the 80 m² field requires 1,600 slates before edge courses, cuts or breakage. If your supplier states a mass per slate, enter it to obtain net slate mass. No universal weight is assumed for Welsh, Spanish or reclaimed material.
The installed-cost triple is £118.75 / £211.88 / £305 per m² before VAT. At the midpoint, the covering allowance is £16,950.40. Standard VAT adds £3,390.08, producing £20,340.48, displayed as approximately £20,500. Leadwork, scaffold, strip-out, battens and membrane are excluded unless confirmed additional quotes are entered.
Slate roof cost per m2 UK
| Price observation | Published GBP/m² | Scope |
|---|---|---|
| Checkatrade natural slate | £160–275 | Supply and fit |
| MyJobQuote slate material | £95–275 | Material only |
| MyJobQuote general labour | £30–60 | Added to material for comparison |
Read 1 October 2026: Checkatrade roof installation and MyJobQuote new roof costs. The constructed material-plus-labour comparison is £125–335/m². Tax basis is not explicit, so the model accommodates both possibilities before blending net rates. This generic slate allowance does not establish a sourced Welsh premium, a Spanish discount or a reclaimed-slate rate.
Lead valleys and the supporting roof
Measured leadwork is priced as metres times your quoted before-VAT rate. Confirm its width, detailing and installation scope with the roofer; a flashing strip and a valley are different jobs. Battens and membrane should only be added when they are genuinely outside the supplied-and-fitted covering quote. The quantity takeoff and installed budget answer different questions: changing headlap changes field coverage, but does not automatically change a generic per-area installation allowance.
A heavier covering can require a structural check, and heritage consent may restrict the source, colour or size of replacement slate. Reclaimed material also needs grading for reuse. Do not treat a net slate count as an order list with all special pieces and waste included.
Compare tile with the UK roof replacement cost calculator. Price an extension with the flat roof replacement cost calculator UK, an outbuilding with the garage roof replacement cost calculator UK, and check the angle using the roof pitch calculator.