Roof Tiling & Slating
In England and Wales, a waterproof underlay is laid across the trusses and held down by the roofing or tile battens. In Scotland, there is a requirement for sarking boarding beneath this underlay with counter battens beneath the roofing battens.
Types of Tiles
Interlocking concrete tiles are perhaps the most cost-effective of the roof coverings. These are large tiles that cover around ten to the metre. They are laid as a single lap, side by side with the grooves on the underside of the one tile resting within those on the upper side of the preceding tile.
Plain tiles come in both concrete, and clay forms with the hand made clay tiles being the most expensive. The coverage rate is around sixty to the square metre, so there is a consequent increase in labour. Additionally, as the tiles are laid double or treble lapped (i.e. each tile has part of up to two other tiles beneath it) there is a great deal more battening needed and the weight on the roof is significantly increased. Plain tiles are often used for tile hanging.
Pantiles are usually made from clay. Traditionally, they are single lapped with the downward roll of each tile simply rolling over the upward roll of the preceding tile. Modern alternatives in both clay and concrete often emulate the look of the pantile while using the technology of the interlocking tile.
Types of Slate
Slates vary from region to region. They are usually laid treble lapped with each slate nailed to the batten. These days, slates are imported from places as far away as China, Spain and Canada. Additionally, there are many man-made slates on the market made from either fibre and cement or moulded with a mixture of slate dust and glass fibre resin. Some of these combine with the technology of the interlocking tile in order to create a slate effect single lapped roof.
Perhaps the most expensive mainstream roofing option is to use stone slates. These are enormously heavy slabs of natural stone laid in slightly different patterns from region to region. They are most commonly seen in areas such as the Cotswolds and the Pennines. They are very expensive to both buy and lay. Once again man has stepped in to copy them, and there are now acceptable concrete moulded imitations. However, these copies are by no means cheap.
In Scotland, all roofs must be covered with a rigid sarking board over which the underslating felt is laid with a counter batten beneath the roofing battens. If a breathable membrane slating/sarking felt is used then the need for ventilation at the ridge or soffit may be negated so long as there is a counter batten creating clear space below and above the membrane.