WO2015118355A1

WO2015118355A1 - Interlocking tile and tiled roof including such tiles

Info

Publication number: WO2015118355A1
Application number: PCT/GB2015/050354
Authority: WO
Inventors: John Fifield
Original assignee: Forticrete Limited
Priority date: 2014-02-07
Filing date: 2015-02-09
Publication date: 2015-08-13
Also published as: EP3105391A1; GB2522888A; AU2015213846A1; ZA201606070B; GB201402181D0; GB2522888B

Abstract

An interlocking tile having a tile body that extends between an underlock and an overlock. The overlock has a recess for receiving a ridge of an underlock of a neighbouring tile in a roof, and the recess of the overlock is of decreasing depth when viewed in a direction towards the tile body. The thinnest part of the interlock is therefore spaced away from the tile body.In the event that a force is applied to the overlock, for example if it is stepped on, the spacing of the thinnest part of the interlock away from the tile body reduces the bending moment at the thinnest part, thereby increasing the strength of the interlock.

Description

INTERLOCKING TILE AND TILED ROOF INCLUDING SUCH TILES

Field of the invention The invention relates to interlocks for roofing tiles. Background to the invention

The primary function of a roof is to protect a lower space below the roof from external elements such as wind and precipitation. A typical pitched roof includes a plurality of parallel load-bearing rafters that slope from a ridge at the top of the roof structure to an eave at a lowermost edge of the roof structure, and a plurality of parallel battens disposed on top of, and extending orthogonally with respect to, the rafters. Roof covering elements such as tiles are affixed along the battens in horizontally- extending rows or courses. Each course of tiles underlaps the course of tiles directly above and overlaps the course of tiles directly below, such that the tiles overlap in a ridge-to-eave direction. The tiles typically incorporate certain features to prevent precipitation penetrating between the tiles. For example, left and right sides of each tile may be provided with complementary interlocking features so that left-to-right neighbouring tiles are arranged to interlock with one another to guard against water penetration between neighbouring tiles of a course.

Figures 1 and 2 illustrate in perspective and cross-sectional views respectively a typical roofing tile 20 having such interlocking features. An upwardly-facing left underlock 22a projects from a left side 24 of the main body 21 of the tile 20. In the tile 20 shown in Figure 1 , the left underlock 22a does not extend all the way down, but instead stops short of the end of the tile 20 to define a cut-out 26, although in other tile variations the underlock may extend the full length of the tile. A downwardly-facing right overlook 22b, not visible in Figure 1 but visible in Figure 2, is incorporated into the underside of the tile 20 at the right-hand side 26. The overlook stops short of the lower edge of the tile 20 to define a closer 25 that corresponds to the cut-out 26 of the underlock 22a. The underlock 22a and overlook 22b have uniform cross sections in a ridge-to-eave direction (apart from the closer 25 and cut-out 26 at the lower edge of the tile 20) and have complementary elongate ridges 28 and recesses 30 defined by orthogonal walls. Figure 3 illustrates schematically and in cross-section left and right interlocks 22a, 22b of neighbouring left- and right-hand tiles 20a, 20b in a roof with their left and right interlocks 22a, 22b are arranged to interlock with one another.

When in use, the right overlook 22b of the left-hand tile 20a is placed over the left underlock 22a of the right-hand tile 20b. In this way, the left-hand tile 20a covers the left underlock 22a of the right-hand tile 20b, such that the interlocks 22a, 22b are not visible when the tiles 20a, 20b are installed on a roof. This disguising of the interlocks 22a, 22b is further aided by the cut-out 26 of the left underlock 22a and closer 25 on the right overlook 22b (see Figure 1), which prevents the left underlock 22a being visible from below.

When the interlocks 22a, 22b are arranged to interlock with one another, a ridge 28a of the left underlock 22a is received in a recess 30b of the right overlook 22b, and a ridge 28b of the right overlook 22b is received in a recess 30a of the left underlock 22a. By virtue of the ridges 28 and recesses 30, a tortuous path is created between the interlocks 22a, 22b in a right-to-left direction. This tortuous path reduces water penetration between neighbouring tiles 20a, 20b. Any water that does penetrate between the neighbouring tiles 20a, 20b is caught in the interlocks 22a, 22b, where it drains away onto the surface of the tiles 20 in the course below.

The interlocks 22a, 22b described therefore provide an effective means for guarding against ingress of water between left-to-right neighbouring tiles in a course. However, the interlocks 22a, 22b are necessarily thinner than the main body 21 of the tile 20, and are therefore inherently a point of weakness of the tile 20. In particular, if a downward-facing interlock (which in the orientation illustrated is the right overlook 22b, but may

alternatively be the left underlock 22a if the tile 20 is inverted) is subjected to a downward bending moment, for example as a result of a worker stepping on the tile 20, the overlook, 22b is vulnerable to fracture, particularly at a junction 23 between the overlook, 22b and the main body 21 of the tile 20, where the bending moment is the highest. Thus, the thickness of the interlocks 22a, 22b, must be sufficiently large to provide the required strength. In practice, this limits the thickness of the tiles, because if the thickness of the tile were reduced, the thickness of the interlocks 22a, 22b would also be reduced, such that the interlocks 22a, 22b would be unacceptably weak.

It would be desirable to mitigate or overcome at least one of the problems described above.

Statements of the invention

Against this background, the invention resides in an interlocking tile having a tile body that extends between an underlock and an overlook, the overlook having a recess for receiving a ridge of an underlock of a neighbouring tile in a roof, the recess of the overlook being of decreasing depth when viewed in a direction towards the tile body.

Because the recess of the overlook is of decreasing depth when viewed towards the tile body, the overlook is correspondingly of increasing thickness when viewed towards the tile body. In this way, a thinnest part of the overlook is spaced away from a junction between the interlock and the tile body.

The strength of the interlock is proportional to its thickness. Thus, by virtue of the invention, the weakest point of the interlock is spaced away from the junction between the interlock and the tile body. When a force is exerted on the overlook, for example as a result of someone stepping on the overlook, the overlook is subjected to a bending moment. The greatest bending moment is felt at the junction between the overlook and the main body, and the bending moment decreases moving outwardly from that junction. By virtue of the invention, the weakest part of the interlock is spaced away from the region subjected to the highest bending moment and towards a region subjected to a lower bending moment. Thus, the bending moment at the point of fracture is lower than in a conventional tile. In this way, the interlock can withstand greater stresses, or can be made thinner while still withstanding the same stresses. Thus, by virtue of the recess of the overlook being of decreasing depth looking towards the tile body, the thickness of the interlock, and therefore the thickness of the whole tile, can be reduced. The overlook may meet the tile body at a junction region and the junction region may have a thickness that is less than a thickness of the tile body. The recess of the overlook may be of decreasing depth when viewed in a direction towards the junction region so as to space the thinnest part of the interlock away from the junction region. By making the junction region thinner than the tile body, a space is defined beneath the overlook all the way up to the tile body that is sufficiently large to receive the underlock of a neighbouring tile in the roof. The underlock can therefore be accommodated beneath the overlook so as to extend right up to the tile body. In this way, the interlocking effect can be securely established using relatively short interlocks, without the need to extend the length of the tile overlook, which would otherwise increase the bending moment exerted if a force were applied to the overlook.

The junction region, may, for example, have a thickness that is approximately half the thickness of the tile body. In this way, the thickness of the junction region and the thickness of the underlock accommodated beneath it may be substantially equal, allowing substantially equal thickness of the overlook and the underlock.

The tile body may comprise an outer surface beneath the junction region that defines a side wall of the recess. When the tile is in use, the underlock may be located against or in the vicinity of the sidewalk

To achieve the decreasing depth, the recess may have a base wall, and at least a portion of the base wall may be inclined. For ease of manufacture, the inclined portion of the base wall may have a gradient between approximately 1 :2 and approximately 1 : 10.

The underlock of the tile may have a ridge configured to be received in a recess of an overlook of a neighbouring tile in a roof. The ridge may be of increasing height when viewed in a direction towards the tile body. In this way, the recess of the overlook and the ridge of the underlock may complement one another to allow for a secure interlock between the tiles, and to allow the underlock to extend all the way up to the tile body if required.

To achieve the increasing height of the ridge, the ridge may have an inclined surface. Alternatively, the increasing height may be achieved by providing stepped portions of the ridge, such that one or more ledges are defined being of increasing height towards the tile body.

In embodiments that include a recess having an inclined base wall and a ridge having an inclined surface, an angle of inclination of the inclined base wall may be substantially equal to an angle of inclination of the inclined surface of the ridge. In this way, when neighbouring tiles are arranged to interlock, the inclined base wall of the recess and the inclined surface of the ridge may be substantially parallel, such that they can lie closely against one another, thereby evenly transferring load from one tile to another.

In some embodiments, a portion of the recess that is remote from the tile body may be of substantially constant depth.

A thinnest portion of the first interlock may have a thickness of less than approximately 8 mm.

To provide improved strength at both the underlock and the overlook, the underlock and overlook may each comprise a recess that is of decreasing depth when viewed in a direction towards the tile body.

The recess of the overlook may be provided with a locator configured to be received in a recess of the underlock of the neighbouring tile in a roof. Such a locator allows neighbouring tiles to be quickly and easily located with respect to one another as they are laid in the roof.

The locator may be a ridge provided at an end of the overlook.

The tile may be a rolled tile, and the overlook may be located substantially at an apex of the roll.

From another aspect, the invention resides in an interlocking tile having a tile body that extends between an underlock and an overlook, the underlock having a ridge and the overlook having a recess for receiving a ridge of an underlock of a neighbouring tile in a roof, the recess of the overlook having a base wall, at least a portion of which is inclined such that the recess is of decreasing depth when viewed in a direction towards the tile body, and the ridge having an upper surface, at least a portion of which is inclined such that the ridge is of increasing height when viewed in a direction towards the tile body, wherein the inclined portion of the upper surface of the ridge and the inclined portion of the base wall of the recess are inclined at substantially the same angle.

The invention also extends to a tiled roof comprising a plurality of the tiles described above, each tile being arranged to interlock a neighbouring tile in a left-to-right direction. It will be appreciated that preferred and/or optional features of one aspect of the invention may be used alone, or in appropriate combination, with other aspects of the invention also.

Brief description of the drawings

Reference has already been made above by way of introduction to the invention to Figures 1 and 2 of the drawings, which are perspective and cross-sectional views respectively of a conventional interlocking tile, and to Figure 3 of the drawings, which is a schematic cross-section of left and right interlocks 22a, 22b of neighbouring left- and right-hand tiles 20a, 20b in a roof with their left and right interlocks 22a, 22b arranged to interlock with one another.

In order that the invention may be more readily understood, reference will now be made to the remainder of the drawings, in which:

Figure 4 is a perspective view of an interlocking tile according to an embodiment of the invention;

Figure 5 is a cross-sectional view of the tile of Figure 4 along the line A-A;

Figure 6 is a partial enlarged cross-sectional view of the tile of Figure 4 along the line A-A;

Figure 7 is a partial enlarged cross-sectional view of an overlook forming a part of the tile of Figure 4, taken along the line B-B of Figure 4; Figure 8 is a cross-sectional view of a right overlook forming part of the tile of Figure 4 arranged to interlock with a left underlock of a neighbouring tile in a roof;

Figure 9 is a partial cross-sectional view of the right overlook of Figure 8 in isolation;

Figure 10 is a schematic cross-sectional view of a right overlook of a conventional tile with a force applied to the interlock; and Figures 1 1 and 12 are schematic cross-sectional views of right overlooks of tiles according to embodiments of the invention with a force applied to each interlock.

Detailed description of embodiments of the invention Figures 4 and 5 illustrate a tile 40 having a tile body 41. The tile body 41 extends generally in a tile plane between first and second tile interlocks 42a, 42b at left and right sides 44, 45 of the tile 40. Only one interlock 42a is visible in Figure 4, but both interlocks 42a, 42b are visible in Figure 5. A first or left interlock 42 is an underlock that extends along, and projects outwardly from, a left side 44 of the tile 40. The left underlock 42a is upwardly-facing. As seen in Figure 4, the left underlock 42a stops short of a lower end of the tile 40, to define a cut-out 43.

A second or right interlock 42b is an overlook (see Figure 5) that extends along a right side 45 of the tile 40 on the tile's undersurface. The right overlook 42b is downwardly- facing. Although not visible in Figure 4, the right overlook 42b stops short of the lower end of the tile 40, to define a closer that corresponds to the cut-out 43.

When a plurality of such tiles 40 are arranged in courses on a roof, left-to-right neighbouring tiles 40 within the course are arranged to interlock with one another, such that the left underlock 42a of each tile underlaps a right overlook 42b of a tile to its left, while the right overlook 42b of each tile overlaps a left underlock 42a of a tile to its right. This interlocking arrangement guards against the ingress of water between neighbouring tiles in a course. As best seen in Figure 5, a lower surface 46 of the left underlock 42a forms part of a lower surface 48 of the tile 40, while an upper surface 50 of the left underlock 42a includes interlocking formations in the form of a ridge 52a and a recess 54a. Conversely, an upper surface 58 of the right overlook 42b forms part of an upper surface 60 of the tile 40, while a lower surface 62 of the right overlook 42b includes interlocking formations in the form of a ridge 52b and a recess 54b. The ridges 52a, 52b and recesses 54a, 54b of each interlock 42a, 42b run along the entire length of the interlock 42a, 42b.

The cross-section of each of the left and right interlocks 42a, 42b in an eave-to-ridge direction will now be described in more detail with reference to Figure 6.

Considering firstly the left underlock 42a, and moving from an outer side of the left underlock 42a towards the tile body 41 , the ridge 52a of the left underlock 42a is defined by left and right faces 64a, 64b and an upper face 66 that joins the left and right faces 64a, 64b. Junctions between the left, right and upper faces 64a, 64b, 66 are optionally radiused, to provide generally rounded corners for ease of manufacture.

The upper face 66 of the ridge 52a is tapered downwardly and outwardly. In this way, the ridge 52a of the left underlock 42a is of increasing height looking towards the tile body 41.

Moving inwardly from the ridge 52a, is the recess 54a of the left underlock 42a. The recess 54a is of generally rectangular cross section, and is defined by left and right side walls 68a, 68b and a horizontal base wall 70 that joins the left and right sidewalls 68a, 68b. Junctions between the left and right side walls 68a, 68b and the base wall 70 are optionally radiused, to provide generally rounded corners for ease of manufacture.

The left side wall 68a of the recess 54a is provided by the right face 64b of the ridge 52a, and is generally orthogonal to the horizontal base wall. The right sidewall 68b is tapered, so that the right sidewall 68b extends generally inwardly and upwardly.

Continuing inwardly from the recess 54a, a joining portion 69 of generally rectangular cross section joins the underlock 42a to the tile body 41 , and also acts to space the recess 54a away from the tile body 41. The joining portion 69 has an upper surface 67 that is generally horizontal. Turning now to the right overlook 42b, and moving again from an outer side of the right overlook 42b towards the tile body 41 , at the outer side of the right overlook 42b is a ridge 52b of the right overlook 42b. The ridge 52b is defined by left and right faces 72a, 72b, and a lower face 74 that joins the left and right faces 72a, 72b. The right face 72b of the ridge 52b forms an end face of the right overlook 42b. The lower face 74 leads into the left face 72a of the ridge 52b, which is tapered such that the left face 72a extends inwardly and upwardly.

Continuing inwardly, the recess 54b of the right overlook 42b is defined by a left or inner sidewall 76a that is defined by an outer surface of the tile body 41 , a right or outer sidewall 76b and a base wall 78 that joins the left and right sidewalls 76a, 76b. The recess 54b has a depth d that is defined as the vertical distance between the base wall 78 and a plane p that is generally parallel to the plane of the tile and that meets the lower face 74 of the ridge 52b.

The base wall 78 of the recess 54b is tapered, such that it extends inwardly and downwardly. In this way, the recess 54b of the right overlook 42b is of decreasing depth when viewed in a direction towards the tile body 41. Thus, in the region of the recess 54b, a thickness of the right overlook 42b in a direction generally orthogonal to a plane of the tile 40 increases when viewed in a direction towards the tile body 41.

The left side wall 76a of the recess 54b is sloped so as to extend steeply into the tile body 41. The recess 54b, and hence the right overlook 42b, meets the tile body 41 at a junction region 80. The junction region is of a thickness that is less than the thickness of the tile body. In this way, a space is defined beneath the junction region 80 that, in use, receives the underlock 42a of a neighbouring tile in the roof, and allows the underlock 42a to be accommodated right up to the tile body 41. Beneath the junction region 80 is an outer surface of the tile body that defines a left side wall 76a of the recess 54b. Figure 7 illustrates the cross section of the overlook 42b towards the top end of the tile 40. Towards the top end of the tile, the recess 54b is provided with a locator 71. The locator 71 takes the form of a short ridge that extends down the overlook 42b by a length of approximately 20 mm. The ridge 71 has a curved lower surface 73 and extends downwardly so as to stand proud of the ridge 52b of the overlook 42b. Figure 8 illustrates the interlocking relationship between left and right interlocks 42a, 42b of neighbouring left and right tiles 40a, 40b in a course when the tiles 40 are arranged in a roof. When left and right tiles 40a, 40b are arranged to interlock with one another, the ridge 52a of the left underlock 42a is received in the recess 54b of the right overlook 42b. The upper face 66 of the ridge 52a is inclined at substantially the same angle as the base wall 78 of the recess 54b, such that the upper face 66 of the ridge 52a and the base wall 78 of the recess 54b lie snugly against one another.

The ridge 52b of the right overlook 42b rests on the upper surface 67 of the joining portion 69 of the left underlock 42a.

Figure 8 reveals that the base wall 78 of the recess 54b of the right overlook 42b is longer than the upper face 66 of the ridge 52a of the left underlock 42a. In this way, when the tiles are laid on a roof, there is a degree of tolerance in the relative positioning of the left and right tiles 40a, 40b in a left-to-right direction.

Referring back to Figure 7, at the upper end of the tile 40, the locator 71 helps to locate the neighbouring tiles in the correct relative position when the neighbouring tiles are arranged to interlock. In particular, the locator 71 is located in the recess 54a of the underlock of the neighbouring tile, with the curved lower surface 73 spaced apart from the base wall of the recess 54a by approximately 1 mm. Turning now to Figure 9 of the drawings, the effect of a force F on the right overlook 42b will now be described. Such a force may be exerted, for example, by someone stepping on the overlook 42b when it is on the ground 100, thereby exerting a force F at an outer edge of the overlook 42b. When the force F is exerted on the overlook 42b, the overlook 42b acts as a cantilever, and experiences a bending moment. This bending moment will cause a tensile force to be applied to an upper surface of the overlook 42b, and a compressive force to be applied to a lower surface of the overlook 42b. The tensile force on the upper surface will cause the overlook 42b to fracture if the force F is too great. The strength of the overlook 42b is determined by two factors: firstly the distance between the point where the force is applied and the weakest point of the overlook 42b, indicated by the dimension X on Figure 9, and secondly by the thickness of the interlock at that point, indicated by the dimension Y on Figure 9. Specifically, the strength S of the interlock is proportional to V² and inversely proportional to X, such that:

In a tile manufactured in accordance with the invention, because the recess 54 of the right overlook 42b is of varying depth, the thinnest part of the overlook 42b is not at the junction region 80 between the tile body 41 and the overlook 42b, but is instead spaced horizontally from that junction region 80 by a distance Z. The distance between the applied force F and the weakest point of the overlook 42b is therefore reduced.

Accordingly, because the strength of the overlook 42b is inversely proportional to X, the strength of the overlook 42b is increased.

Figures 10, 1 1 and 12 are comparative schematic illustrations showing the effect of an applied force F on a tile overlook 22b of a conventional tile 20 and on tile interlocks 42b of tiles 40 according to embodiments of the invention. The conventional tile 20 shown in Figure 10 has a tile thickness f' of 18mm. The strength of the overlook 22b is a function of the total interlock length (X) and the thickness of the interlock at its thinness point (Υ'):

Thus, for an interlock length (X) of 25 mm and an interlock thickness (Υ') of 8 mm, the strength is 8² / 25 = 2.56 units.

Figure 1 1 illustrates a tile 40 according to an embodiment of the invention having the same tile thickness t of 18 mm.

The base wall 78 of the overlook 42b is tapered such that the recess 54b is of decreasing depth when viewed towards the tile body 41 of the tile 40. In the example shown in Figure 1 1 , the tapered portion of the base wall 78 has a horizontal length Z of 7 mm, and the base wall 78 tapers by a vertical distance of 1 mm. Because the tile thickness t is maintained, the thickness V of the interlock at the thinnest point is 8 mm, and the thickness V" of the interlock at the junction between the overlook 42b and the tile body 51 is 9 mm. Thus, the thinnest part of the interlock is displaced away from the main body of the tile by the distance Z (7 mm), such that the distance X between the force F and the thinnest part of the tile is X = X' - Z = 18 mm.

Thus, by virtue of the recess 54b being of decreasing depth when viewed towards the tile body 41 , the strength of the tile is increased to 8²/ 18 = 3.56 units. In this way, the strength of the overlook 42b is significantly improved by the presence of the tapered base wall 70.

In the example illustrated in Figure 12, the thickness of the entire tile has been reduced by 1 mm compared to the tile of Figures 9 and 10, to a thickness t = 17 mm.

As in the embodiment of Figure 1 1 , the base wall 78 of the overlook 42b is tapered is tapered such that the recess 54b is of decreasing depth when viewed towards the tile body 41. Because the thickness of the tile has been reduced by 1 mm, the thickness of the overlook 42b has been correspondingly reduced, such that the thinnest part of the overlook 42b has a thickness Y of 7 mm, which tapers to a thickness of 8 mm at the junction 80 between the overlook 42b and the tile body 41. The length of the tapered portion of the base wall 78 remains 7 mm, such that the distance X remains 18 mm.

In this case the reduction of the tile thickness reduces the strength of the interlock to I²1 18 = 2.72 units. The strength of the overlook 42b of the tile 40 of Figure 12 is therefore lower than the strength of the overlook 42b of the tile 40 of Figure 1 1 , but is still greater than the strength of the overlook 22b of the conventional tile 20 illustrated in Figure 8, despite the thickness of the entire tile being reduced by 1 mm. Thus, the invention provides a means for increasing the strength of the tile overlook 42b, which therefore allows the thickness of the entire tile 40 to be reduced.

Increasing the strength of the interlock means that the tile interlock is less prone to breaking when it is handled before being laid on a roof. This reduces the chance of tiles having broken interlocks being incorporated into roofs, and hence improves the overall performance of the tiles and roofs incorporating those tiles. Reducing the thickness of the tile reduces the volume and thereby the weight of the tile. In the examples described above, the tile thickness can be reduced by 1 mm to a thickness of 17 mm, representing a 5.6 % decrease in weight. For a typical tile weight of around 45kg per square metre of roof, this amounts to a significant weight saving of

2.5 kg per square meter of roof. The tiles are also easier to transport, can be stored more efficiently, and are more visually appealing when laid on a roof.

Although in the embodiments described the tile is a plain tile, it will be appreciated that this need not be the case, and the tile may be, for example, a rolled tile, and may be a double-rolled tile. Where the tile is a rolled tile, the invention has particularly

advantageous effect when the tile is configured such that the overlook is disposed substantially at an apex of the roll. In the embodiment described, only the right overlook has a recess that is of increasing depth when viewed in a direction towards the main body of the tile. However,

embodiments are envisaged in which both the left and right interlocks have recesses that are of increasing depth when viewed in a direction towards the main body of the tile, or in which only the left interlock has a recess that is of increasing depth when viewed in a direction towards the main body of the tile.

It need not necessarily be the case that the entire recess is of increasing depth when viewed in a direction towards the main body of the tile; instead it may be the case that only a portion of the recess is of increasing depth when viewed in a direction towards the main body of the tile.

A locator may be provided alternatively or additionally on the underlock, or the locator may be omitted altogether if desired. The cut-out of the underlock, and the closer of the underlock may also be omitted.

It will be appreciated that many variations and modifications not explicitly described above are also possible without departing from the scope of the invention as set forth in the appended claims.

Claims

1. An interlocking tile having a tile body that extends between an underlock and an overlook, the overlook having a recess for receiving a ridge of an underlock of a neighbouring tile in a roof, the recess of the overlook being of decreasing depth when viewed in a direction towards the tile body.

2. The interlocking tile of Claim 1 , wherein the overlook meets the tile body at a junction region, the junction region having a thickness that is less than a thickness of the tile body, and the recess of the overlook is of decreasing depth when viewed in a direction towards the junction region so as to space the thinnest part of the interlock away from the junction region.

3. The interlocking tile of Claim 2, wherein the junction region has a thickness that is approximately half the thickness of the tile body.

4. The interlocking tile of Claim 2 or Claim 3, wherein the tile body comprises an outer surface beneath the junction region that defines a side wall of the recess of the overlook.

5. The interlocking tile of any preceding claim, wherein the recess has a base wall, at least a portion of which is inclined.

6. The interlocking tile of Claim 5, wherein the inclined portion of the base wall has a gradient between approximately 1 :2 and approximately 1 : 10.

7. The interlocking tile of any preceding claim, wherein the underlock has a ridge configured to be received in a recess of an overlook of a neighbouring tile in a roof, the ridge being of increasing height when viewed in a direction towards the tile body.

8. The interlocking tile of Claim 7, wherein the ridge has an inclined surface.

9. The interlocking tile of Claim 8 when dependent on Claim 5, wherein an angle of inclination of the base wall of the recess is substantially equal to an angle of inclination of the inclined surface of the ridge.

10. The interlocking tile of any preceding claim, wherein a portion of the recess that is remote from the tile body is of constant depth.

1 1. The interlocking tile of any preceding claim, wherein a thinnest portion of the first overlook has a thickness of less than approximately 8 mm.

12. The interlocking tile of any preceding claim, wherein the underlock and overlook each comprise a recess that is of decreasing depth when viewed in a direction towards the tile body.

13. The interlocking tile of any preceding claim, wherein the recess of the overlook is provided with a locator configured to be received in a recess of the underlock of the neighbouring tile in a roof.

14. The interlocking tile of Claim 13, wherein the locator is a ridge provided at an end of the overlook.

15. The interlocking tile of any preceding claim, wherein the tile is a rolled tile, and the overlook is located substantially at an apex of the roll.

16. An interlocking tile having a tile body that extends between an underlock and an overlook, the underlock having a ridge and the overlook having a recess for receiving a ridge of an underlock of a neighbouring tile in a roof, the recess of the overlook having a base wall, at least a portion of which is inclined such that the recess is of decreasing depth when viewed in a direction towards the tile body, and the ridge having an upper surface, at least a portion of which is inclined such that the ridge is of increasing height when viewed in a direction towards the tile body, wherein the inclined portion of the upper surface of the ridge and the inclined portion of base wall of the recess are inclined at substantially the same angle.

17. The interlocking roof tile of Claim 16, wherein the overlook meets the tile body at a junction region, the junction region having a thickness that is less than a thickness of the tile body, and the recess of the overlook is of decreasing depth when viewed in a direction towards the junction region so as to space the thinnest part of the interlock away from the junction region.

18. The interlocking tile of Claim 17, wherein the junction region has a thickness that is approximately half the thickness of the tile body.

19. The interlocking tile of Claim 17 or Claim 18, wherein the tile body comprises an outer surface beneath the junction region that defines a side wall of the recess of the overlook.

20. A tiled roof including a plurality of interlocking tiles according to any preceding claim, each tile being arranged to interlock a neighbouring tile in a left-to-right direction.

21. An interlocking tile substantially as hereinbefore described with reference to Figures 4 to 9, 1 1 and 12 of the accompanying drawings.