Concrete Roof Tile

A concrete roof tile is a tile made from a mix of sand, cement and water, coloured with pigment, formed in a mould or by extrusion and then cured. Concrete tiles are produced in profiles that imitate clay pantiles, Spanish S-tiles, flat slates and plain tiles, and are one of the most common roof coverings on new housing in several countries.

History

The earliest known concrete roof tiles were made in the 1840s by Adolph Kroher at Grassau in Bavaria, Germany. Kroher sold cement and moulds so that householders could make their own tiles, which led to inconsistent quality. Factory production with mechanical extrusion in the 20th century made concrete tiles cheap and uniform, and they became widespread in the United Kingdom, continental Europe, Australia, South Africa and the southern and western United States.

Properties

• Weight: concrete tiles are thick and among the heaviest common roofing materials, so the roof structure must be designed for them. A typical UK concrete-tiled roof has rafters at 600 mm (about 24 in) centres with battens at about 300 mm (12 in).
• Absorption: concrete is more porous than well-fired clay; moisture absorption of about 13% is commonly cited, and resealing every 3-7 years is recommended in some climates.
• Colour: comes from pigment mixed through the concrete or from a coloured surface slurry. Surface colour can fade over time, and old concrete roofs are often repainted or recoated.
• Life: concrete tiles are usually expected to last about 30-50 years, compared with 100 years or more for high-quality clay.
• Heat: when laid with an air gap between tile and deck, tiles reduce heat transfer from the sun into the building.

Profiles

• Flat or slate-look tiles.
• Low-profile interlocking tiles with shallow rolls.
• High-profile S-tiles that imitate Spanish or mission clay tiling.
• Concrete plain tiles, laid double-lap in the English manner.

Most concrete tiles are interlocking and single-lap, hung on battens by nibs and nailed or clipped in exposed areas.

Maintenance issues

Common problems include surface erosion that exposes the sand aggregate, moss and lichen growth on the rough surface, cracked tiles from foot traffic, and weathered mortar at ridges and hips. Many current systems use dry-fix ridges with mechanical clips instead of mortar.