Clay can be excavated, moulded and burned without any expensive or elaborate machinery and for centuries clay roofing tiles have been used. There are two qualities of tile: Hand made tiles are moulded from a sandy clay which is pressed into shape by hand pressure so that even if some form of screw press is used the clay will not be heavily compacted. During burning the tiles shrink and there are quite noticeable variations which give a tiled roof attractive appearance. The tiles vary in colour from light brick red to almost black and many of the more expensive tiles are sand faced produce the rough texture which is popular. Handmade tiles fairly readily absorb water and should not be laid at a pitch of less than 45°to horizontal. If laid at a less pitch these tiles may become saturated in winter and frost will then cause them to disintegrate. Machine pressed tiles are made from selected pure clays which are thoroughly ground to a fine condition. The clay is mixed with