WO2011095799A1

WO2011095799A1 - Green roofs and modules therefor

Info

Publication number: WO2011095799A1
Application number: PCT/GB2011/050157
Authority: WO
Inventors: Peter Martin Broatch
Original assignee: Peter Martin Broatch
Priority date: 2010-02-03
Filing date: 2011-02-01
Publication date: 2011-08-11
Also published as: GB201001706D0; GB2477499A

Abstract

A roof tile (60) for a green roof (68) has a tray portion (20) for containing a vegetation growth medium (62) over a substantial expanse of the tile (60). Interlocking portions (24, 26) extend adjacent the side edges (16, 18) of the tile (60) and are configured so that one interlocking portion (24) of one tile (60) can be overlapped by the other interlocking portion (26) of another such tile (60) and guide rainwater which may fall between the tiles (60) to the lower edge (14) of the tiles. The tray portion (20) stops short of the upper edge (12) of the tile, and a support portion (22) extends between the tray portion (20) and the upper edge (12) so that the tray portion (20) of one tile (60) can overlap the support portion (22) of another such tile (60) so that the tray portions (20) of the tiles (60) are substantially contiguous. The growth medium (62) is in the form of beads (62), and the tile has a mesh (64) covering the growth medium (62) and attached to the upper edges (12) of the peripheral walls (32, 34) of the tray portion (20). The sizes of the mesh (64) and beads (62) are such that the majority of the beads (62) cannot pass through the mesh (64).

Description

Green roofs and modules therefor

This invention relates to green roofs and in particular to modules for making green roofs.

A green roof is a roof of a building that, when mature, is partially or completely covered with soil or other growing medium and vegetation such as grass or sedum.

It should be noted that although most green roofs, when mature, are green in colour, they are not necessarily so. Therefore, for the purposes of this specification, the term 'green roof' is not intended to denote any particular colour of the roof.

Green roofs provide a number of advantages over conventional roofs. They reduce the heating and cooling requirements of the building by increasing the thermal insulation of the roof. They reduce the cooling requirements of a building by evaporation of water absorbed by the roof. They can therefore combat the 'heat island' effect in urban areas. They reduce the rate of storm water run-off from the roof. They convert carbon dioxide to oxygen by photosynthesis. They can filter pollutants. They can improve the acoustic insulation of the roof - soil tends to filter out lower acoustic frequencies, and vegetation tend to filter out higher frequencies. They can increase the wildlife habitat in built-up areas. They can in many cases increase the life span of the roof.

Some known green roofs are constructed from modules which are placed on a weatherproof sub-roof. A module can be temporarily removed for maintenance or be replaced by another module.

Some known green roofs are flat roofs, i.e. horizontal and not pitched, or are pitched at a low angle. They can formed by placing growing medium on a weatherproof sub-roof and may be provided with baffle boards in an attempt to prevent movement, for example slippage, of the growing medium on the sub-roof.

One aim of the present invention, or least of specific embodiments of it, is to provide a green roof which is substantially waterproof in itself.

Another aim of the present invention, or at least of specific embodiments of it, is to provide a green roof which can be constructed from modules which can be prepared with a growing medium before they are installed.

A further aim of the present invention, or at least of specific embodiments of it, is to provide a module for a green roof which, after it has been prepared with a growing medium, can be transported to its installation site and handled and installed without much care being required, and which after installation provides protection against the growing medium being washed away by rain or blown away by the wind.

In accordance with a first aspect of the invention, there is provided a roof tile for a pitched green roof. The tile has a tray portion for containing a vegetation growth medium over a substantial expanse of the tile. The tile has an upper edge, a lower edge which in use is disposed on the roof beneath the upper edge, and first and second side edges. The tile has first and second elongate interlocking portions adjacent its first and second side edges, respectively, and extending substantially parallel to the side edges. The interlocking portions are configured so that the first interlocking portion of one such tile can be overlapped by the second interlocking portion of a second such tile and guide rainwater which may fall between the tiles to the lower edge of the tiles. For example, the first interlocking portion preferably has at least one elongate channel extending substantially parallel to the side edges of the tile for guiding rainwater which may fall between the tiles to the lower edge of the tiles. A row of such interlocking tiles at the same level on the roof can therefore substantially block penetration of rainwater between the tiles.

The first interlocking portion preferably projects beyond the tray portion and the second interlocking portion is preferably provided beneath the tray portion so that, when two such tiles are interlocked, the tray portions of the tiles are substantially contiguous. Once mature, the vegetation growing from a pair of adjacent tray portions in the same row of tiles can therefore merge.

The tray portion preferably stops short of the upper edge of the tile, in which case the tile preferably has a support portion which extends between the tray portion and the upper edge of the tile, with the tile being configured so that, adjacent the lower edge of one such tile, the tray portion can overlap the support portion of a second such tile so that the tray portions of the tiles are substantially contiguous. By having lower part of an upper tile which overlaps an upper part of a lower tile, rainwater which may penetrate between the tiles can be caught. Also, once mature, the vegetation growing from a pair of adjacent tray portions in upper and lower rows of tiles can merge.

This feature may be provided independently of the first aspect of the invention. Therefore, in accordance with a second aspect of the invention, there is provided a roof tile for a pitched green roof, wherein: (i) the tile has a tray portion for containing a vegetation growth medium over a substantial expanse of the tile; (ii) the tile has an upper edge, a lower edge which in use is disposed on the roof beneath the upper edge, and first and second side edges; (iii) the tray portion stops short of the upper edge of the tile; (iv) the tile has a support portion which extends between the tray portion and the upper edge of the tile; and (v) the tile is configured so that, adjacent the lower edge of one such tile, the tray portion can overlap the support portion of a second such tile so that the tray portions of the tiles are substantially contiguous.

The support portion preferably has a collection portion which is arranged to collect rainwater which may fall between two such tiles, in which case, the tile preferably has at least one passageway in use to permit such rainwater to drain from the collection portion to the tray portion of that tile.

The support portion preferably has a downwardly projecting portion in use to enable the tile to be hooked onto a roofing batten.

The tray portion preferably has a lower wall extending substantially parallel to the lower edge of the tile in order to help prevent growth medium slipping downwardly out of the tray portion. The lower wall preferably has at least one passageway in use to permit water in the tray portion to drain out of the tray portion, so that the tray portion does not readily become waterlogged. However, the or each passageway in the lower wall is preferably in use above the lowermost level of the interior of the tray portion, in order to help retain some water in the tray portion which will, during dry periods, sustain vegetation growing from the tray portion.

The tray portion preferably has an upper wall and a pair of side walls extending substantially parallel to the upper edge and the side edges of the tile, respectively, in order to help retain the growth medium in the tray portion.

The tiles are preferably such that, when two or more such tiles are interlocked in use, the upper edges of the upper, lower and side walls of the tray portions are substantially coplanar. Once the vegetation is mature, this assists in hiding the fact that the roof is formed from tiles and provides a substantially flat, but pitched, roof face.

The tile may be supplied, ready for building into a roof, with tray portion already containing a growth medium. The growth medium may be in the form of at least one block, which may for example be trapped in the tray portion or which can readily be held by hand in the tray portion when the roof tile is being handled. Alternatively, the growth medium may be particulate, in which case the tile preferably further includes means for retaining the majority of the growth medium in the tray portion in the event that the tile is turned upside down. This assists in enabling the growth medium to be kept in the tray portion during transportation and installation and, after installation, during stormy or windy weather, especially before the vegetation has matured.

These latter features may be provided independently of the first and second aspects of the invention and may be applied to roof tiles for flat (i.e. non-pitched) roofs. Therefore, in accordance with a third aspect of the present invention, there is provided a roof tile for a green roof, wherein: (a) the tile has a tray portion extending over a substantial expanse of the tile; (b) the tray portion has a first pair of opposed peripheral walls and a second pair of opposed peripheral walls; and (c) either: (i) the tray portion contains at least one block of a vegetation growth medium; or (ii) the tray portion contains a particulate vegetation growth medium and the tile further includes means for retaining the majority of the growth medium in the tray portion in the event that the tile is turned upside down.

In one embodiment, the retaining means comprises a mesh covering the growth medium and attached to the upper edges of the upper, lower and side walls of the tray portion. The size of the mesh and the particulate size of the growth medium are preferably such that at least the majority of the growth medium cannot pass through the mesh. At least a substantial proportion of the growth medium is preferably in the form of beads, for example formed of light expanded clay aggregate.

In the roof tile of any of the aspects of the invention, the roof tile may be supplied, ready for building into the roof, with the tray portion already containing plant seeds and/or sprouts, or more mature vegetation. In the case of seeds or sprouts, they are preferably attached to the growth medium and/or tray portion by adhesive.

The tray portion may be subdivided into a plurality of compartments by dividing walls extending substantially parallel to the upper and lower edges of the tile and/or the first pair of peripheral walls to maintain an approximately uniform distribution of the growth medium in the tray portion. The dividing walls may also serve to reinforce the tray portion. In this case where a covering mesh is employed, the mesh is preferably also attached to the upper edges of the dividing walls so that it is more securely attached and also to prevent growth medium migrating between compartments.

When used for a pitched roof, each dividing wall preferably has at least one passageway in use to permit water in an upper such compartment to drain into a lower such compartment, so that the upper compartment does not readily become waterlogged. However, each passageway is in use preferably above the lowermost level of the interior of the respective upper compartment, in order to help retain some water in the compartment which will, during dry periods, sustain vegetation growing from that compartment. In a pitched roof, the water levels in the compartments of a single tile will therefore be different relative to each other, but similar relative to the vegetation growing from the respective compartment.

The tray portion may also be subdivided into a plurality of compartments by dividing walls extending substantially parallel to the side edges of the tile and/or the second pair of peripheral walls and serving to reinforce the tray portion.

In combination, some of the features described above result in a green roof tile which can be readily transported, handled and installed, and which performs in a single modular element all of the required functions of waterproofing the roof, retaining the growth medium, draining the growth medium and water storage for the vegetation.

A specific embodiment of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:
Figure 1 is an isometric view of a plastics moulding for roof tile viewed from its lower left corner and above;
Figure 2 is an isometric view of the moulding viewed from its top left corner and below;
Figure 3 is an elevation viewed towards the lower edge of the moulding;
Figure 4 is similar to Figure 3, but sectioned on the section line 4-4 shown in Figure 5;
Figure 5 is an elevation viewed towards the left edge of the moulding;
Figure 6 is similar to Figure 5, but sectioned on the section line 6-6 shown in Figure 3;
Figure 7 is an isometric view of a mesh cover for the roof tile;
Figure 8 is similar to Figure 6, but also including growth medium and the mesh cover;
Figure 9 is an isometric view of the roof tile viewed from its lower left corner and above;
Figure 10 is a sectioned view of a part of a roof taken on the section line 10-10 shown in Figure 11;
Figure 11 is a sectioned side view of part of a roof;
Figure 12 is an isometric view of a plastics moulding for left-end half-tile viewed from its lower left corner and above; and
Figure 13 is an isometric view of a plastics moulding for right-end half-tile viewed from its lower left corner and above.

Referring to Figures 1 to 6, a moulding 10 for a roof tile is formed from any suitable plastics material such as polypropylene. The moulding 10 has an upper edge 12, a lower edge 14, a left edge 16 and a right edge 18. The moulding 10 provides a tray portion 20, a support portion 22, and left interlocking portion 24 and a right interlocking portion 26.

The tray portion 20 is generally rectangular as viewed from above and covers the main expanse of the moulding 10. The tray portion 20 has a bottom 28 formed by a base panel 30 of the moulding 10, an upper wall 32, a lower wall 34, a left side wall 36 and a right side wall 38. The

side walls

34,36 are at right angles to the base panel 30 and progressively increase in height from the lower wall 34 to the upper wall 32. The upper wall 32 is inclined towards the upper edge 12 of the moulding 10 by an angle approximately equal to the angle at which the roof in which the tile will used is pitched to the horizontal, so that the upper wall becomes generally upright in use. The lower wall 34 has a lower portion which is generally at right angles to the base panel 30 and an upper portion which is inclined towards the upper edge 12 of the moulding 10 at a similar angle to the upper wall 32. The tray portion 20 is subdivided by a number of dividing walls 40 extending between the

side walls

36,38 and parallel to, and inclined at a similar angle to, the upper wall 32. The upper edges of the dividing walls 40, the upper and

lower walls

32,34 and the left and

right side walls

36,38 are all coplanar. A number of reinforcing ribs 42 extend between adjacent pairs of the

walls

32,34,40. The ribs 42 may reach to the same height as the

adjacent walls

32,34,40, or, as shown in the drawings, they may be shorter. Each of the upper and

lower walls

32,34 and the dividing walls 40 is perforated with a row of holes 44, each approximately the same height above the bottom 28 of the tray portion 20 and each below the height of the lower wall 34.

The support portion 22 is formed by part of the base panel 30 of the moulding which extends beyond the upper wall 32 of the tray portion 20. The support portion 20 has a number of ribs 46 on the upper face of the base panel 30 including at its sides, each extending upwardly to the same level. A hook portion 48 projects downwardly from the base panel 30 along the upper edge 12 of the moulding 10. A pair of nail holes 49 are formed in the base panel 30 in the region of the support portion 22.

The left interlocking portion 24 projects to the left from the left side wall 36 of the tray portion 20 and has an upper surface formed with ridges and a pair of upwardly facing channels 50 extending parallel to the left edge 16 of the moulding 10.

The right interlocking portion 26 is recessed into the underside of the tray portion 20 along its right side and has a downwardly facing surface formed with channels and a pair of downwardly directed ridges 52 extending parallel to the right edge 18 of the moulding 10. The right interlocking portion 26 is of a complementary configuration to the left interlocking portion 24, as will be described in more detail later.

Both interlocking

portions

24,26 extend from the lower edge 14 of the moulding to beyond the upper wall 32 of the tray portion 20.

Referring now also to Figures 7 and 8, in order to produce a roof tile 60 using a moulding 10 as described above, the compartments formed between the

walls

32,34,36,38,40 of the tray portion 20 are filled with growth medium in the form of beads 62 of light expanded clay aggregate (LECA). Seeds of, for example, sedum may also be loosely added to the tray portion, or they may glued to the beads 62 with any suitable adhesive that is harmless to the seeds and their ability to germinate. Alternatively, seeding of the roof tile 60 may be left until after it has been installed in a roof. The tray portion 20 is then covered by a rectangle of plastics mesh 64 which is glued or welded to the upper edges of the

walls

32,34,36,38,40 of the tray portion 20. The outline size of the mesh 64 is such that it does not substantially overhang the upper, lower and

side walls

32,34,36,38 of the tray portion. The beads 62 may typically have a diameter between 4 mm and 10 mm, and the mesh may typically have openings which are 3 mm square so that the beads 62 are trapped in the tray portion 20.

The completed roof tile 60 is shown in Figure 9.

Referring now to Figures 10 and 11, a number of such identical roof tiles 60 are shown fitted onto a roof frame structure so as to form a pitched roof 68. The roof frame structure has a number of rafters 70 and a number of horizontally extending battens 72. The battens 72 are fixed to the rafters 70 so that the centre-to-centre pitch P of adjacent battens 72 is slightly larger than the length L of the trays portions 20 of the roof tiles 60 between the upper edges of the upper and

lower walls

32,34.

Starting with the lowermost course of the tiles 60 and progressing from right to left, each tile 60 is in turn placed onto two battens 72 with its hook portion 48 hooked over the upper batten 72 and so that its right interlocking portion 26 overlaps and engages with the left interlocking portion 24 of the previous tile 60, as shown in Figure 10, so that the right side wall 38 of the tray portion 20 of the left tile 60 engages with the left side wall 36 of the tray portion 20 of the left tile 60. The tile 60 is fixed in place by driving nails 74 through its nail holes 49 into the upper batten 72. Once the first course has been completed, the next course is fitted in a similar way, preferably with the tiles 60 of adjacent courses by staggered by one half of the width of the tray portions 20. As can be seen in Figure 11, the tray portion 20 of each tile 60 in the upper course overlaps the supporting portions 22 of two tiles 60 in the lower course, with the lower wall 34 of the tray portion 20 of the upper tile 60 closely spaced from the upper walls 32 of the tray portions 20 of the lower tiles 60. Building of the roof continues in this fashion until the uppermost course of tiles 60 has been fitted, which is then finished with a course of ridge tiles. At the ends of each course, a half-tile may be fitted which has a

moulding

10L,10R similar to a left half (Figure 12) or a right half (Figure 13), as appropriate, of the moulding 10 of the full tiles 60 and has a plain far end wall 76L,76R.

It will be appreciated from Figures 10 and 11 that the meshes 64 of all of the tiles 60 in the roof 68 are coplanar. Once the seeds in the tray portions 20 have germinated and vegetation has grown out of the tray portions 20 through the meshes 64, the vegetation will, from the outside, hide the fact that the roof 68 is formed from individual tiles 60, and the roof 68 will appear as a continuous plain expanse of vegetation.

In the event of rain, the rain will fall on the vegetation and much of it will pass through the vegetation and meshes 64 into the tray portions 20 of the tiles 60. The rain can collect in each compartment between the

walls

32,34,40 of the tray portion 20 up to the level of the holes 44 in the

lower wall

34,40 of that compartment (as shown by diamond hatching 76 in Figure 11), but above that, the rain will drain through the holes 44 into the next lower compartment. From the lowermost compartment of each tile 60, excess rain will drain through the holes 44 in the lower wall 34 of the tray portion 20 and fall onto the support portions 22 of the adjacent tiles 60 in the next lower course of tiles 60. From the support portion 22 of each tile 60, rain can drain (when it reaches a sufficiently high level) through the holes 44 in the upper wall 32 of the tray portion 20 of that tile 60 into its uppermost compartment. Any rain that finds its way into the space between the lower wall 34 of an upper tile 60 and the upper wall 32 of a lower tile 60 will likewise fall onto the support portion 22 of the lower tile 60. Any rain that finds its way between the left and

right side walls

36,38 of two adjacent tiles 60 in the same course will drop into one or both of the channels 50 of the left interlocking portion 24 of the right tile 60. The rain will then flow down along the channels 50 and fall onto the support portion 22 of the tile 60 in the next lower course.

It will be appreciated that many modifications and developments may be made to the embodiment of the invention described above.

For example, as shown in Figure 12, in order to facilitate moulding, rather than holes 44 being formed in the

walls

32,34,40 to permit water drainage, slots 78 may be employed which extend up to the upper edges of the

walls

32,34,40.

Also, as shown in Figure 12, the nail holes 49 may be surrounded by bosses 80 of increased thickness for increased strength and to prevent water penetration through the nail holes 49.

Furthermore, as shown in Figure 12, the upper edges of the

walls

32,34,36,38,40,76L, 76R may be formed with upwardly projecting posts 82 which engage with the mesh 64 and are then melted down to lock the mesh 64 in place.

Although the growth medium has been described above as being of LECA beads 62, it may be formed by other particulate material. Furthermore, some of the growth medium may be such that, in itself, it could pass through the mesh 64. For example, the growth medium could contain a proportion of soil, sand and/or compost. In this case, the growth medium is preferably pressed into the compartments in the tray portion 20 while damp so that the growth medium as a whole sticks together, and none or very little of the growth medium will be able to pass through the mesh 64 even if the tile 60 is turned upside down.

Alternatively, the growth medium for each tray portion may be in the form of a block, or several blocks, one for each compartment between the

walls

32,34,40. In this case, the block or blocks of growth medium may be loosely fitted into the compartments, or they may be trapped for example by lips along the upper edges of the

walls

32,34,36,38,40,76L,76R or by a mesh 64.

It should be noted that the embodiment of the invention has been described above purely by way of example and that many other modifications and developments may be made thereto within the scope of the present invention.

Claims

A roof tile (60) for a pitched green roof (68), having:

a tray portion (20) for containing a vegetation growth medium (62) over a substantial expanse of the tile;

an upper edge (12), a lower edge (14) which in use is disposed on the roof beneath the upper edge, and first and second side edges (16,18); and

first and second elongate interlocking portions (24,26) adjacent the first and second side edges, respectively, and extending substantially parallel to the side edges, the interlocking portions being configured so that the first interlocking portion of one such tile can be overlapped by the second interlocking portion of a second such tile and guide rainwater which may fall between the tiles to the lower edge of the tiles.
A roof tile as claimed in claim 1, wherein:

the first interlocking portion (24) has at least one elongate channel (50) extending substantially parallel to the side edges for guiding rainwater which may fall between the tiles to the lower edge of the tiles.
A roof tile as claimed in claim 1 or 2, wherein:

the first interlocking portion projects beyond the tray portion and the second interlocking portion is provided beneath the tray portion so that, when two such tiles are interlocked, the tray portions of the tiles are substantially contiguous.
A roof tile as claimed in any preceding claim, wherein:

the tray portion stops short of the upper edge of the tile;

the tile has a support portion (22) which extends between the tray portion and the upper edge of the tile; and

the tile is configured so that, adjacent the lower edge of one such tile, the tray portion can overlap the support portion of a second such tile so that the tray portions of the tiles are substantially contiguous.
A roof tile (60) for a pitched green roof (68), wherein:

the tile has a tray portion (20) for containing a vegetation growth medium (62) over a substantial expanse of the tile;

the tile has an upper edge (12), a lower edge (14) which in use is disposed on the roof beneath the upper edge, and first and second side edges (16,18);

the tray portion stops short of the upper edge of the tile;

the tile has a support portion (22) which extends between the tray portion and the upper edge of the tile; and

the tile is configured so that, adjacent the lower edge of one such tile, the tray portion can overlap the support portion of a second such tile so that the tray portions of the tiles are substantially contiguous.
A roof tile as claimed in claim 4 or 5, wherein:

the support portion has a collection portion which is arranged to collect rainwater which may fall between two such tiles; and

the tile has at least one passageway (44.78) in use to permit such rainwater to drain from the collection portion to the tray portion of that tile.
A roof tile as claimed in any of claims 4 to 6, wherein:

the support portion has a downwardly projecting portion (48) in use to enable the tile to be hooked onto a roofing batten (72).
A roof tile as claimed in any preceding claim, wherein:

the tray portion has a lower wall (34) extending substantially parallel to the lower edge of the tile.
A roof tile as claimed in claim 8, wherein:

the lower wall has at least one passageway (44,78) in use to permit water in the tray portion to drain out of the tray portion.
A roof tile as claimed in claim 9, wherein:

the or each passageway in the lower wall is in use above the lowermost level of the interior of the tray portion.
A roof tile as claimed in any preceding claim, wherein:

the tray portion has an upper wall (32) and a pair of side walls (36,38) extending substantially parallel to the upper edge and the side edges of the tile, respectively.
A roof tile as claimed in claim 11 when directly or indirectly dependent on claim 8, wherein:

the tiles are such that, when two or more such tiles are interlocked in use, the upper edges of the upper, lower and side walls of the tray portions are substantially coplanar.
A roof tile as claimed in any preceding claim, wherein:

the tray portion contains at least one block of a vegetation growth medium.
A roof tile as claimed in any of claims 1 to 12, wherein:

the tray portion contains a particulate vegetation growth medium (62); and

the tile further includes means (64) for retaining the majority of the growth medium in the tray portion in the event that the tile is turned upside down.
A roof tile (60) for a green roof (68), wherein:

the tile has a tray portion (20) extending over a substantial expanse of the tile;

the tray portion has a first pair of opposed peripheral walls (32,34) and a second pair of opposed peripheral walls (36,38); and

either:

the tray portion contains at least one block of a vegetation growth medium;

or

the tray portion contains a particulate vegetation growth medium (62); and

the tile further includes means (64) for retaining the majority of the growth medium in the tray portion in the event that the tile is turned upside down.
A roof tile as claimed in claim 14 or 15, wherein:

the retaining means comprises a mesh (64) covering the growth medium and attached to the upper edges of the upper, lower and side walls of the tray portion.
A roof tile as claimed in claim 16, wherein:

the size of the mesh and particulate size of the growth medium are such that at least the majority of the growth medium cannot pass through the mesh.
A roof tile as claimed in any of claims 14 to 17, wherein:

at least a substantial proportion of the growth medium is in the form of beads (62).
A roof tile as claimed in claim 18, wherein:

the beads are formed of light expanded clay aggregate.
A roof tile as claimed in any preceding claim, wherein:

the tray portion contains plant seeds and/or sprouts.
A roof tile as claimed in claim 20 when dependent on any of claims 13 to 19, wherein:

the seeds and/or sprouts are attached to the growth medium and/or tray portion by adhesive.
A roof tile as claimed in any preceding claim, wherein:

the tray portion is subdivided into a plurality of compartments by dividing walls (40) extending substantially parallel to the upper and lower edges of the tile and/or the first pair of peripheral walls.
A roof tile as claimed in claim 22 when directly or indirectly dependent on claim 16, wherein:

the mesh is attached to the upper edges of the dividing walls.
A roof tile as claimed in claim 22 or 23, wherein:

each dividing wall has at least one passageway (44,78) in use to permit water in an upper such compartment to drain into a lower such compartment.
A roof tile as claimed in claim 24, wherein:

each passageway is in use above the lowermost level of the interior of the respective upper compartment.
A roof tile as claimed in any preceding claim, wherein:

the tray portion is subdivided into a plurality of compartments by dividing walls (42) extending substantially parallel to the side edges of the tile and/or the second pair of peripheral walls.
A roof (68) having a roof covering provided by a plurality of roof tiles (60) as claimed in any preceding claim.