How many roof tiles do I need per square metre?

It depends on the tile type. Interlocking concrete tiles (e.g., Marley Modern, Redland 49) need approximately 10 tiles per m². Plain clay or concrete tiles need approximately 60 tiles per m² due to their much smaller size and double lap. Natural slates vary from 20-30 per m² depending on size. Always check the manufacturer's data sheet for the specific tile, as coverage varies with headlap and gauge.

What is batten gauge?

Batten gauge is the spacing between the top edges of consecutive rows of tile battens. It determines how much of each tile is exposed (the margin). Gauge is calculated from the tile length, headlap, and any adjustment for alignment at the ridge and eaves. For example, a plain tile (265 mm long) with a 65 mm headlap has a gauge of 100 mm. Interlocking tiles with 75 mm headlap on a 420 mm tile have a gauge of 345 mm.

What weight can my roof structure support?

A typical UK domestic roof structure is designed for a total load of 0.75-1.5 kN/m² (including tiles, battens, felt, and wind/snow loads). Concrete interlocking tiles weigh approximately 42-48 kg/m², plain clay tiles approximately 70-77 kg/m², and natural slate approximately 25-55 kg/m² depending on thickness. If re-roofing with heavier tiles than the original, a structural check of the rafters and trusses is advisable.

What is the minimum pitch for different tile types?

Minimum pitches vary by tile type and exposure zone: interlocking concrete tiles typically require 15-22.5° minimum, plain tiles require 35° minimum, natural slates require 20-25° minimum depending on size, and fibre cement slates require 15-20° minimum. In severe exposure zones (coastal, high altitude), these minimum pitches increase. The manufacturer's fixing specification should be followed.

How do I calculate waste for roof tiles?

Add 5% waste for simple rectangular roofs, 7.5% for roofs with hips, and 10-12.5% for complex roofs with valleys, dormers, and multiple hips. You also need to add ridge tiles (approximately 3 per linear metre), hip tiles, valley tiles, eaves tiles, and verge tiles as separate items. Half tiles or tile-and-a-half tiles are needed at verges to maintain the bond pattern.

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Roof Tile Coverage Rates per m² by Type

UK roof tile coverage rates, batten gauge, minimum pitch, and tiles per square metre for concrete, clay, slate, and interlocking tiles.

Interlocking Concrete Tiles

Tile	Tiles/m²	Gauge (mm)	Min Pitch	Weight (kg/m²)
Marley Modern	10.0	345	17.5°	43
Redland 49	10.2	340	17.5°	44
Marley Mendip	9.7	343	15°	47
Redland Renown	9.7	340	15°	48
Redland Grovebury	10.0	338	15°	47

Interlocking Clay Tiles

Tile	Tiles/m²	Gauge (mm)	Min Pitch	Weight (kg/m²)
Marley Ashmore	10.0	340	17.5°	50
Sandtoft 20/20	10.0	340	22.5°	48
Sandtoft Rivius	12.8	280	30°	55

Plain Tiles (Double Lap)

Tile	Tiles/m²	Gauge (mm)	Min Pitch	Weight (kg/m²)
Concrete plain tile (267 x 168)	60	100	35°	75
Clay plain tile (265 x 165)	60	100	35°	70

Natural Slate

Slate Size (mm)	Slates/m²	Gauge (mm)	Min Pitch	Weight (kg/m²)
600 x 300	13.3	250	20°	30-50
500 x 250	21.3	188	22.5°	30-55
400 x 250	26.7	150	25°	30-55

Related Calculators

Use the Roof Tile Calculator for tile quantities, or the Roof Area Calculator to measure your roof. The Batten Calculator works out batten and felt requirements.

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Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.