This invention relates to roof tiles and particularly to a roof tile having complementary interloc ing regions along its sides so that two adjacent such tiles can be interlocked when in use on a roof.

When two such tiles are interlocked, there will be a join extending down from the upper surfaces of the tiles, laterally through the. interlocking regions and then down to the lower surfaces of the tiles. The interlocking regions are contoured such that a longitudinal drainage channel is provided. This will collect water which passes down through the join from the upper surfaces of the tiles and will prevent it passing through the join to the lower surfaces of the tiles and into the roof space. The water will simply run down the roof through the channels.

A problem with known tiles of this type is that wind can interfere with the flow of water through the drainage channel. Wind can fairly easily reach the bottom region of the channel from the upper surfaces of the tiles and this can result in a build up of water within the channel and overflow into the roof space. This problem is made worse if the join extending down from the upper surfaces of the tiles is relatively wide, thus providing greater access to wind. It is preferable for the interlocking region to be so designed as to accomodate a reasonable degree of lateral tolerance or "stretch", to facilitate laying of the tiles, particularly where obstructions such as chimneys, parapet walls or roof lights are encountered. On the other hand, the degree of stretch is limited by the permissible width of join having regard to the desirability of avoiding excessive wind

effects on water in the channels in the interlocking regions.

A further problem is that the joins between existing interlocking tiles of this type can be unsightly due to their visible depth and again this may be worse if the joins are wide.

An object of the present invention is to alleviate some or all of these problems, and thus according to the invention there is provided a roof tile having complementary interlocking regions along its sides, wherein along one side of the tile a portion which will define part of a downwardly extending join from the upper surfaces of two such tiles when interlocked is provided with an outwardly directed step at a position below the upper surface of the tile, and along the other side a complementary portion which will likewise define part of a downwardly extending join from the upper surfaces of two such tiles when interlocked is provided with an inwardly directed recess whose configuration complements that of the step.

Thus, when two such tiles are interlocked the join extending down from the upper surfaces will be stepped with the step on one tile being shielded by the recess on the other. This will reduce the visible depth of the join and will also shield the underlying channel from wind effects. The permissible degree of stretch can correspond to the width of the step but even when the step ceases to be shielded by the recess in an adjacent, interlocked tile, the width of access to the bottom of the channel will be ^" considerably less than the width of the join at the upper surfaces of the tiles. In a preferred embodiment, approximately 5 mm of lateral tolerance or stretch is provided, whereas with a known tile of similar dimensions the fiαure would be of the order of 3 mm.

The improvement of this invention is applicable to a wide range of sizes and shapes of roof tile. As is conventional, the interlocking regions preferably comprise on one side of the tile an upwardly facing channel and on the other side a downwardly facing portion which will project into the channel of a like tile. In such an arrangement, the upwardly facing channel on one side can have the step, projecting up from its base along its inner edge. Thus in a preferred embodiment one side of the channel is defined by the outwardly directed step and one side of the downwardly facing portion is defined by the inwardly directed recess. The complementary recess will be formed in the outermost part along the other side of the tile. The downwardly facing portion may have a width less than the channel, preferably by an amount equal to the width of the step.

The profile of the interlocking region of the tile and the shape in cross section of the drainage channel may vary, and it is envisaged that the interlocking region may define two or more channels arranged side by side, in which case it will be appreciated that still only one step need be provided. The step itself is preferably defined by an upper surface normal to the join and a side surface at an acute angle to the join.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings wherein:

Fig. 1 illustrates in cross section the inter¬ loc ing sides of known roof tiles; and

Figs. 2a, 2b and 2c illustrate in cross section the interlocking sides of roof tiles in accordance with the invention in alte ^r native positions.

Referring firstly to Fig. 1, known interlocking roof tiles 1, 2 of identical shape include complemen¬ tary overlapping interlocking regions 3, 4 at their

side edges. The underlying interlocking region 3 of the tile 1 is provided with a recess defining a drainage channel 5 which collects water which might otherwise penetrate the underlying roof space via the lower part 6 of the join between the tiles which leads down to the lower surfaces of the tiles. As discussed above, a problem with this type of tile is that the drainage channel is partly exposed to the effects of the wind via the upper part of the join 6" extending down to the channel 5 from the upper surfaces of the tile. This problem is enhanced as the spacing in the region of the join part 6' is increased. As such, the degree of lateral tolerance or stretch between the tiles is restricted. As shown in Fig. 2a, tiles 7, 8 in accordance with the invention likewise include overlapping interlocking regions 9, 10 of generally similar configuration to those of the prior art tile discussed above. However, a step 11 is provided adjacent the inner edge of the drainage channel 12 between the base thereof and the upper surface of the tile 7. This step 11 of the underlying interlocking region 9 engages in a complementary recess 13 of the overlying interlocking region 10. Thus, the base of the drainage channel 12 is shielded by the step 11, engaging in the recess 13, from the effects of the wind, and the tendency of the wind to interfere with the flow of water in the drainage channel associated with known tiles is reduced. Furthermore, as shown in Figs. 2b and 2c, the degree of stretch between the tiles may be increased, since the spacing at the upper part 14 of the join between the tiles can be increased to almost to the width of the step 11 without the base of the drainage channel 12 being exposed. A further advangage is that the apparent depth of the tile joint is reduced, since it is the surface of the step 11 which is seen externally rather than the base of the drainaqe channel 12.

It will be appreciated that each tile 7, 8 will include an interlocking region 9 along one side edge and a complementary region 10 along the other edge such that the tiles may be engaged with like tiles on either side. The tiles may be provided with other conventional elements such as ribs and may be made from e.g. concrete in the normal manner.