the tile elements being offset from each other both along a row direction and transverse to a row direction so that one tile element will lie in a row above and laterally offset from the other application_number US 17073588 A description the tiles of these examples are formed as interlocking single lap tiles which may be cast in concrete clay or other suitable material in the embodiment shown in fig2 and 3 each tile 11 comprises four tile elements 12 13 14 and 15 formed as a single unitary cast member each tile element is of similar rectangular shape with the two tile elements 12 and 13 lying side by side in one row position separated by a junction 16 the tile elements 14 and 15 lie side by side in an adjacent lower row separated by a similar junction 17 which is offset laterally relative to the junction 16 the upper edges 18 of each tile have a straight edge whereas the upper surface of the lower edge 19 of each tile is curved as shown fixing holes 20 are provided in each of the upper tile elements 12 and 13 to allow securing of the tiles to wooden battens 21 as shown in fig4 the lateral edges of the tiles 13 and 14 are formed with rectangular channels 22 and 23 respectively to permit interlocking with laterally adjacent tiles each.