Roof Tile Coverage Rates per m² by Type

It depends on the tile type. Large-format interlocking concrete tiles (e.g., Marley Modern, Marley Mendip) need approximately 10 tiles per m². Smaller interlocking tiles (e.g., Redland 49) need approximately 16-17 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 13-27 per m² depending on size. Always check the manufacturer's data sheet for the specific tile, as coverage varies with headlap and 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.

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.

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.

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.