Specification A

Terrain Type: Terrain with numerous large, high and closely spaced obstructions. This category includes large city centres. Mechanically fix two course of tiles at eaves, verges, ridges and one adjacent full tile at valleys, hips and abutments by nailing or wiring as required.

Roof Pitches: 17.5º up to 26º Under tile membrane (Mandatory)
26º up to 45º Under tile membrane (Recommended)
45º up to 55º Under tile membrane (Recommended, each tile to be nailed)
55º up to 90º Under tile membrane (Mandatory, each tile to be nailed)

Specification B

Terrain Type: Terrain with numerous closely spaced obstructions, the size of domestic houses. Includes well-wooded areas, suburbs, town and industrial areas. Mechanically fix a band of tiles, equal to a fifth of the number of courses on the rafter length, at eaves and verges or the full overhang, whichever is the greater, and at ridges and abutments. Fix one full tile adjacent to hips and valleys and every third tile on the rest of the roof. Cut tiles at hips, valleys and abutments must be secured by nailing or wiring. Soffits must be closed at eaves and verge overhangs.

Roof Pitches: 17.5º up to 26º Under tile membrane (Mandatory)
26º up to 45º Under tile membrane (Recommended)
45º up to 55º Under tile membrane (Recommended, each tile to be nailed)

Specification C

Terrain Type: Exposed open terrain with a few, or no obstructions, like open sea coasts and flat, treeless plains with little vegetation. Mechanically fix each tile, soffits must be closed at eaves and verge overhangs.

Roof Pitches: 17.5º up to 45º Under tile membrane (Mandatory, each tile to be nailed)
45º up to 90º Under tile membrane (Mandatory, each tile to be nailed)