While we all know that every building has a roof, and the vast majority are covered with slate, clay or concrete tiles; almost all are taken for granted, until they leak.

Over the last 2000 years the tiled roof has developed to such an extent that the simplicity of its function hides the sophistication of the interaction of each individual component. The roof covering takes the full brunt of the punishment that our climate doles out, be it rain, snow, wind, sun, moss, algae or frost; not forgetting the man made punishment of pollution, aircraft wake vortexing and vandalism. Not surprisingly when a problem occurs it quickly becomes a major issue.

Although the roof covering represents approximately 20 - 50% of the visible external surface area of a building (or if vertical tiling is included, this figure can rise to as high as 80%), the relative cost of the roof in relation to the total building cost is small. If the roof were to fail, the cost of correcting, or replacing the roof covering may easily be greater than the original contract value. This is due to the high cost of access and consequential damages that may occur.

It is far more efficient to resolve the problematic elements of a roof design prior to roofing work commencing, rather than at, or after, the construction stage.