GB2523545A

GB2523545A - Improvements in or relating to tiles

Info

Publication number: GB2523545A
Application number: GB1402180.2A
Authority: GB
Inventors: John Fifield
Original assignee: Forticrete Ltd
Current assignee: Forticrete Ltd
Priority date: 2014-02-07
Filing date: 2014-02-07
Publication date: 2015-09-02
Anticipated expiration: 2034-02-07
Also published as: WO2015118354A1; EP3105390A1; GB2523545B; GB201402180D0; ZA201606071B; AU2015213845A1

Abstract

The roof tile 40 has a curved upper surface, the curve extends between the leading 44 and trailing 48 edges in use. The curve is such that the upper surface and the edge are visible when the tile is laid with several other similar tiles. In use a plane 380 is defined that extends from an eave to a ridge of the roof which meets the upper surface of each tile, for example at point 382. The curvature of the upper surface is such that when the tile is laid, a junction between the leading edge and the upper surface of the tile lies below the plane. The upper surface of the tile mmay have a radius of curvature of between 3 and 5 metres, and preferably between 3.5 and 4.5 metres. Also claimed is a roof using the tiles. The tiles may have a secondary purpose such as being a ventilation tile or soil sack terminal.

Description

Improvements in or relating to tiles

Field of the Invention

The invention relates to roof tiles.

Background to the invention

Figure 1 illustrates in cross section a pitched roof 20 for protecting a lower space below the roof from external elements such as wind and precipitation. The pitched roof 20 includes a plurality of parallel load-bearing rafters 22 that slope from a ridge 24 at the top of the roof to an eave 26 at a lowermost edge of the roof 20, and a plurality of parallel battens 28 disposed on top of, and extending orthogonally with respect to, the rafters 26.

An angle between the rafters 28 and a horizontal plane defines a pitch of the roof 10.

Roof-covering elements such as tiles 30 are affixed along the battens in horizontally-extending rows or courses. As can be seen in Figure 1, each course of tiles 30 underlaps the course of tiles 30 directly above and overlaps the course of tiles 30 directly below, such that the tiles 30 overlap in a ridge-to-eave direction, with a leading edge 34 of each tile 30 exposed, and a trailing edge 32 of each tile 30 covered by the tile 30 in the course above.

The tiles may be, for example, flat tiles 130 of the type illustrated in Figures 2 and 3, having an upper surface 131 that is flat. Such flat tiles 130 typically have a uniform body thickness t of approximately 18 mm to 20 mm.

The tiles may also be, for example, cambered tiles 230 of the type illustrated in Figure 4 and 5, in which an upper surface 231 of each tile is curved. In this example, the upper surface 231 has a radius of curvature of approximately 1.6 m.

Referring now to Figure 6, the curvature of the upper surface 231 of such cambered roof tiles 230 is limited by the manufacturing process. The tiles 230 are typically shaped to the desired curvature by moulding the tile body on the surface of a rotating drum 200 having a radius equal to the desired radius of curvature of the tile 230: in this case, 1.6 m. The drum 200 must be accommodated at the manufacturing site as part of the production line, and so the size of the drum 200, and hence the radius of curvature of the tile 230, is limited by the available space. In particular, a radius of curvature greater than approximately 2.5 metres is impractical.

A particular advantage of a cambered tile 230 is that once the main body of the tile 230 has been formed using the drum 200, the curvature of the upper surface allows the tiles 230 to be thinned from the underside at the leading and trailing edges 32, 34, so that thickness is tapered towards the leading and trailing edges 34, 32 of the tile 230. In the embodiment shown, the thickness t' at the leading edge 34 of the tile 230 is reduced to approximately 12 mm, while at the centre of the tile 230 the thickness can be maintained at approximately 18 mm to provide the necessary strength.

This reduction in thickness at the leading edge 234 of the cambered tile 230 compared to the flat tile 130 illustrated in Figures 2 and 3 reduces the amount of wind-driven precipitation that penetrates between the tiles 30 of neighbouring upper and lower courses in the roof 20, as will now be explained.

Referring back to Figure 1, as incoming wind hits the roof 20, the wind is directed upwardly by the pitch of the roof 20, such that wind blows across the roof tiles 30 from the eaves 26 to the ridge 24 in a direction W (see Figure 1). The upwardly-driven wind tends to drive rain between the upper and lower tiles 30. This is particularly significant in low-pitched roofs, which term is understood in the art to mean roofs having a pitch less than 30°, where wind-driven rain is particularly problematic.

The problem of wind-driven rain is exacerbated further by turbulence that is caused when wind that is driven up the roof 20 hits the leading edge 34 of the tile 30. When wind hits the leading edge 34, turbulence is caused in front of the leading edge 34 in the region of the overlap between the upper and lower tiles 30. This turbulence tends to drive rain between the upper and lower tiles 30 at the overlap, which increases the ingress of rain between the tiles 30 and into the roof 20.

The greater the height of the leading edge 34, the more the turbulence, and hence the greater the ingress of precipitation in the presence of driving rain. Thus, the cambered tile 230 of Figures 4 and 5, which has a leading edge 34 having a height of approximately 12 mm, exhibits less ingress of precipitation and hence a better driving rain performance than the flat tile 130 of Figures 2 and 3, which has an leading edge 134 having a height of approximately 18 to 28 mm.

This difference is illustrated by comparative wind-driven rain tests conducted on a roof incorporating flat tiles 130 and a roof incorporating cambered tiles 230 having a radius of curvature of 1.6 m. In tests conducted with a driving rain index (DRI) of 0.5 m2s and at a wind speed of 13.4 ms, the water-recovery was found to be 42 % for the roof incorporating flat tiles 130, and 54 % for the roof incorporating cambered tiles 230, showing an improvement of 29 % in the water-recovery rate.

To improve the driving rain performance further, and as is visible in Figures 3 and 5, each tile 130, 230 may be provided with weather checks 136, 236 of the sort described in the Applicant's granted patent GB2454709. The weather checks 136, 236 are ridges disposed on the undersurface of the tile 130, 230 that, in a tiled roof 20, rest on the upper surface of a tile 130, 230 in the course below. The weather checks 136, 236 guard against ingress of precipitation by increasing the tortuosity of the upward path of precipitation.

While reducing the height of the leading edge 34 of the tile 30 and incorporating weather checks 136, 236 guard against ingress of precipitation between upper and lower tiles 30 to some extent, they are not able to mitigate the problem of wind-driven rain entirely.

Therefore, it would be desirable to improve the wind-driven rain performance of roof tiles still further.

Statements of the invention

Against this background, the invention resides in a roof tile having a curved upper surface that extends between leading and trailing edges, the upper surface and the leading edge being visible when the tile is laid with a plurality of similar tiles to form a roof having a plane that extends from an eave of the roof to a ridge of the roof and meets the upper surface of each tile, wherein a curvature of the upper surface of the tile is such that, when the tile is laid, a junction between the leading edge and the upper surface of the tile lies below the plane.

When such a roof tile is laid in a roof, wind blows up the roof in the from the eaves towards the ridge in the plane that meets the upper surface of each tile. Because the junction between the leading edge and the upper surface of the tile lies below the plane, the wind does not hit the junction as it is driven up the roof but instead hits the upper surface of the. In this way, the driven wind substantially avoids the junction of the tile.

Thus, the problem of additional turbulence being caused in front of the leading edge of the tile as a result of the driven wind catching the junction between the leading edge and the upper surface is substantially avoided. Turbulence in front of the of the leading edge is therefore lower in a roof incorporating tiles made according to the invention than in a roof incorporating the known tiles and the tendency for rain to be driven between the tiles is therefore correspondingly lower.

The upper surface of the tile may have a radius of curvature that is between approximately 3.0 m and approximately 5.0 m. In particular, the upper surface has a radius of curvature that is between approximately 3.5 m and 4.5 m.

The roof tile may have a length between the leading and trailing edges that is greater than 400 mm.

A thickness of the tile at the leading edge may be greater than 12 mm.

In particular, the tile may be thinned from the underside, such that a thickness at the leading edge is lower than a thickness at a centre of the tile. In such a tile, a thickness of greater than 12 mm at the leading edge is particularly advantageous, as such a thickness allows for a sufficiently high thickness at a centre of the tile.

The curvature of the upper surface of the tile may be such that the plane meets the upper surface of the tile at a location that is spaced away from the leading edge of the tile by a distance that is less than 150 mm.

When a plurality of such tiles is laid in a roof, an overlap region between upper and lower neighbouring tiles in the roof is typically 150 mm or less. In this way, the plane meets the upper surface at a location that is in the overlap region. Thus, as wind is directed up the roof, the wind tends to hit the upper surface of each tile in the overlap region.

The roof tile may have a specific secondary purpose. For example, the roof tile may be a ventilation tile, or a soil stack terminal.

From another aspect, the invention resides in a tiled pitched roof including a plurality of roof tiles and having a plane that extends from an eave of the roof to a ridge of the roof and meets the upper surface of the tiles in the roof, each tile having a curved upper surface that extends between leading and trailing edges, the upper surface and the leading edge being visible, wherein a curvature of the upper surface of the tiles is such that a junction between the leading edge and the upper surface of each tile lies below the plane.

The tiles of the roof may be tiles of the type described above.

From another aspect, the invention resides in a roof tile having a curved upper surface that extends between leading and trailing edges, the upper surface and the leading edge being visible when the tile is laid with a plurality of similar tiles to form a roof having a plane that extends from an eave of the roof to a ridge of the roof and meets the upper surface of each tile, wherein a curvature of the upper surface of the tile is such that, when the tile is laid in the roof, the plane meets the upper surface at a point that is spaced away from the leading edge and towards the trailing edge of the tile.

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

Figure 1, which illustrates in cross-section a roof having a plurality of conventional roof tiles, Figures 2 and 3, which illustrate a known flat roof tile in perspective and side views respectively, Figures 4 and 5, which illustrate a known cambered roof tile in perspective and side views respectively, and Figure 6, which illustrates schematically apparatus for making the tile of Figures 4 and 5, have already been described above by way of background to the invention. In order that the invention might be more readily understood, reference will now be made, by way of example only, to the remaining drawings, in which: Figure 7 is a perspective view of a tile according to an embodiment of the invention; Figures 8 and 9 are left and right side views of the tile of Figure 7; Figure 10 is a sectional view of the tile of Figure 7; Figure 11 illustrates the radius of curvature of the tile of Figure 7; Figure 12 illustrates schematically apparatus for making the tile of Figure 7; Figure 13A is a partial cross section of a roof incorporating a plurality of the known flat tiles of Figures 2 and 3, and Figure 13B is a partial enlarged view of Figure 13A; Figure 14A is a partial cross section of a roof incorporating a plurality of the known cambered tiles of Figures 4 and 5 and Figure 148 is a partial enlarged view of Figure 14A; and Figure 15A is a partial cross section of a roof incorporating a plurality of the tiles of Figure 7, and Figure 15B is a partial enlarged view of Figure iSA.

It will be appreciated that the terms left, right, upper, lower and so on refer to the orientation of a tile when it is incorporated in a roof. However, the tile may also be arranged in other orientations, for example during manufacture and/or storage.

Detailed description of embodiments of the invention Figures 7 to 10 illustrate a roof tile 40 having an upper surface 42 that extends between a leading edge 44 at a lower end 46 of the tile 40, and a trailing edge 48 at an upper end of the tile 40. The upper surface 42 also extends left-to-right between a left edge 52 and a right edge 54. An underlock 56 protrudes from the left edge 52 of the tile 40. A length of the tile 40 between the leading and trailing edges 44, 48 is approximately 420 mm.

At the lower and upper ends 46, 50 of the tile 40, the leading and trailing edges 44, 48 join the upper surface 42 to an undersurface 60 of the tile. In this way, the leading edge 44 defines a wall that is generally eaves-facing when the tile 40 is laid in a roof, and the trailing edge forms a wall that is generally ridge-facing when the tile 40 is laid in a roof.

The leading and trailing edges 44 of the tile 40 each meet the upper surface 42 of the tile 40 to define a junction 45. Adjacent to the junction 45, the leading edge 44 is radiused to define a radiused portion 47.

As best seen in Figures 8 to 10, hanging nibs 58 depend downwardly from the undersurface 60 of the tile 40 at its upper end 50. Nail holes 62, visible in Figures 7 and 10, are provided in the upper surface 42 and extend through the tile thickness 40. To lay the tile 40 on a roof, the tile 40 is hung on a batten using the hanging nibs 58, and fixed to the batten using fixing means such as nails or screws that extend through the nail holes 62.

The upper surface 42 of the tile 40 is gently cambered. Thus, when the tile 40 is viewed from the left or right side, as shown in Figures 7 and 8, the upper surface 42 defines a curve having a substantially constant curvature.

As illustrated in Figure 11, the curve of the upper surface 42 defines an arc that is a section of a circle. The radius of curvature of the upper surface 42 is equal to the radius R of the circle. The upper surface 42 of the tile 40 therefore has a radius of curvature R, and a curvature xc of hR.

As has been described above by way of background to the invention, conventional cambered tiles 230 of the sort illustrated in Figures 4 and 5 are moulded on the surface of a drum. With a view to simplifying the manufacturing process and thereby reducing manufacturing costs, the inventors replaced the drum-moulding method described above with a method using apparatus 100 illustrated schematically in Figure 12. In this new method, the tile 40 is moulded on a curved surface 102. The curve of the curved surface 102 forms a partial section of a circle having a radius of curvature H. Unlike in the conventional apparatus illustrated in Figure 6, in which the radius of curvature R is limited to approximately 2.5 m by the available space, in the apparatus illustrated in Figure 12, the radius of curvature His not limited by space constraints. By contrast, a higher radius of curvature H (corresponding to a lower curvature ic of the tile) is preferable, because a higher radius of curvature results in less disruption to the tile as it is moved through the production line and over the curved surface 102.

Thus, for ease of manufacture using the new method described, the radius of curvature R of curved surface 102 of the moulding apparatus 100, and hence the radius of curvature H of the upper surface 42 of the tile 40, is selected to be greater than 2.5 m.

In particular, in the embodiment now described, the radius of curvature R of the upper surface 42 of the tile 40 is approximately 3.5 metres.

While such an increase in the radius of curvature R of the upper surface 42 of the tile 40 relative to a conventional cambered tile 230 facilitates manufacturing, it has a detrimental effect on the degree to which the tile 40 can be thinned from the underside 60. The shallower curvature of the tile 40 means that, to achieve the required threshold thickness at the centre of the tile, the thinning must be correspondingly shallower. As a result, the thickness of the tile 40 at the leading edge 44 is necessarily greater than the thickness of the conventional cambered 130 at its leading edge 134.

In the embodiment now described, the increase of the radius of curvature to 3.5 m results in a thickness of the tile 40 at the leading edge 44 of approximately 14 mm, compared to the leading-edge thickness of 12 mm in a conventional cambered tile 230.

As has been illustrated above by comparison of the driving rain performance of flat tiles and cambered tiles 230, a greater thickness of the tile at the leading edge 44 is known to be detrimental to the driving-rain performance of a tile. Thus, the inventors expected that the tile 40 of Figures 7 to 10, having a leading edge thickness of 14 mm, would display an inferior driving rain performance compared to the conventional cambered tile 230 of Figures 4 and 5, having a leading-edge thickness of 12 mm.

Surprisingly, however, the driving-rain performance of the tile 40 was found to be superior to the driving-rain performance of the conventional cambered tile 230.

When tests were conducted on roofs incorporating the tiles 40 according to the embodiment of the invention described, with a driving rain index (DRI) of 0.5 m2s1 and at a wind speed of 13.4 ms1, the water-recovery was found to be 63 %, compared to 54 % for conventional cambered tiles 230, demonstrating an improvement of 17 %.

Thus the water-recovery rates under identical conditions for roofs 120, 220 incorporating known tiles 130, 230 and for roofs 320 incorporating tiles 40 according to the embodiment of the invention described can be summarised as follows: Radius of Thickness Water Tile curvature at leading recovery (R)/m edge/mm rate/% Flat tile -18 42 Conventional 1 6 12 54 cambered tile New cambered tile 3.5 14 63 On investigation, the inventors determined that the improved driving-rain performance is caused by a change in the passage of upwardly-driven wind over the tiles 40 in the roof 320 as a result of the large radius of curvature R of the upper surface 42 of the tile 40, as will now be described with reference to Figures 13 to 15.

Figures 13a and 13b illustrate a roof 120 incorporating a plurality of flat tiles 130. The tiles 130 of the roof 120 define a plane 180 that extends from the eave 126 of the roof to a ridge 124 of the roof 120 and that just touches each tile 130. In particular, the plane 180 touches each tile 130 at a line of contact 182. The line of contact 182 is located at the junction 135 between the leading edge 134 and the upper surface 131 of the tile 130. In this way, the plane 180 touches each tile 130 along the junction 135.

As wind is driven up the roof 120 in the direction of the arrow W, the driven wind tends to follow the plane 180 in an eave-to-ridge direction. Thus, as the wind is driven up the roof the wind hits the junction 135 between the leading edge 134 and the upper surface 131 of each tile 130, causing turbulence in front of the leading edge 134. This turbulence tends to drive more rain between the upper and lower tiles 130, leading to the relatively low water-recovery rate.

Figures 14a and 14b illustrate another roof 220 incorporating a plurality of conventional cambered tiles 230. The cambered tiles 230 of the roof 220 define a plane 280 that extends from the eave 226 of the roof 220 to the ridge 224 of the roof 220 and that just touches each tile 230 at a line of contact 282.

As in the roof 120 of Figures 13a and 1 3b, the line of contact 282 is at the junction 235 between the leading edge 234 and the upper surface 231 of the tile 230, such that the plane 280 touches each tile 230 across the junction 235.

Thus, when wind is driven up the roof 220 of Figures 14a and 14b, the wind hits the junction 235 of each tile in the manner already described, causing turbulence in front of the leading edge 234 that tends to drive rain between the upper and lower tiles 230.

Figures 15a and 15b illustrate a roof 320 incorporating a plurality of tiles 40 according to the embodiment of the invention illustrated in Figures 7to 10.

The tiles 40 of the roof 320 define a plane 380 that extends from the eave 326 of the roof 320 to the ridge 324 of the roof 320. The plane 380 just touches each tile 40. In the illustrated embodiment, the plane 380 touches each roof tile 40 at a line of contact 382.

By virtue of the higher radius of curvature P of the tiles 40, the line of contact 382 is not disposed at the junction 45 between the leading edge 44 and the upper surface 42 of the tile 40, as is the case in roofs 120, 220 incorporating known tiles 130, 230, but is instead spaced away from the junction 45 towards the trailing edge 48 of the tile 40. In this way, the plane 380 meets the upper surface 42 of each tile 40 substantially tangentially.

Expressed another way, the curvature of the upper surface 42 of the tile 40 is such that, when the tile 40 is laid in the roof 320, the junction 45 between the leading edge 44 and the upper surface 42 of the tile 40 lies below the plane 380.

Figure 1 5b illustrates the location of the line of contact 382 between the plane 380 and the upper surface 42 of the tile 40 in more detail, and in particular shows that the line of contact 382 is located within an overlap region 384 between the tile 40 and a lower tile 40a that is laid directly beneath the tile 40 in the roof 320. Expressed another way, the line of contact 382 is located in the plane 380 at a position that is ridge-wards of the leading edge 44 of the tile 40, and eave-wards of the trailing edge 48 of the tile 40a in the course below.

When tiles 40 are laid in a roof, the overlap region between upper and lower neighbouring tiles is typically less than 150 mm. Thus, the curvature of the upper surface 42 of the tile 40 is such that the point of contact 382 is spaced away from the junction 45 towards the trailing edge 48 of the tile 40 by a distance that is less than 150 mm.

When wind is driven up the roof 320 in the direction of the arrow W, the wind follows the plane 380. Thus, the upwardly-driven wind does not hit the junction 45 between the leading edge 44 and the upper surface 42 of the tile 40, but instead hits the upper surface 42 of the tile 40 at the line of contact 382 that is spaced away from the leading edge 44. In this way, the driven wind substantially avoids the junction 45 of the tile 40.

Thus, in a roof 320 incorporating tiles 40 made according to the invention, the problem of additional turbulence being caused in front of the leading edge 44 of the tile 40 as a result of the driven wind catching the junction 45 between the leading edge 44 and the upper surface 42 is substantially avoided. Turbulence in front of the of the leading edge 44 is therefore lower in a roof 320 incorporating tiles 40 according to the invention than in a roof 320 incorporating the known tiles 130, 230 described, and the tendency for rain to be driven between the tiles 40 is therefore correspondingly lower.

Thus, contrary to the expectations of the inventors, increasing the radius of curvature R of the upper surface 42 of the tile 40 has the surprising effect of improving the driving rain performance of the tile 40.

Although in the embodiment described the upper surface of the tile has a radius of curvature that is approximately 3.5 m, it will be appreciated that the radius of curvature may be varied, so long as the curvature is such that the leading edge of the tile is below the plane when the tile is laid in the roof. For example, the radius of curvature may be between approximately 3.0 m and approximately 5.0 m.

Other dimensions of the tile, including the width and length, may also be varied. The length may be any suitable length, and is preferably at least 400 mm. Although in the roof described the overlap between upper and lower tiles is approximately 150 mm, the overlap may be any suitable length. For example, the overlap may be 100 mm, and correspondingly the curvature of the upper surface of the tile may be such that the plane meets the upper surface of the tile at a location that is spaced away from the leading edge of the tile by a distance that is less than 100 mm.

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

Claims 1. A roof tile having a curved upper surface that extends between leading and trailing edges, the upper surface and the leading edge being visible when the tile is laid with a plurality of similar tiles to form a roof having a plane that extends from an eave of the roof to a ridge of the roof and meets the upper surface of each tile, wherein a curvature of the upper surface of the tile is such that, when the tile is laid, a junction between the leading edge and the upper surface of the tile lies below the plane.
2. The roof tile of Claim 1, wherein the upper surface of the tile has a radius of curvature that is between approximately 3.0 m and approximately 5.0 m.
3. The roof tile of Claim 1, wherein the upper surface of the tile has a radius of curvature that is between approximately 3.5 m and 4.5 m.
4. The roof tile of any preceding claim, wherein the tile has a length between the leading and trailing edges that is greater than 400 mm.
5. The roof tile of any preceding claim, wherein a thickness of the tile at the leading edge is greater than 12 mm.
6. The roof tile of any preceding claim, wherein the curvature of the upper surface of the tile is such that the plane meets the upper surface of the tile at a location that is spaced away from the leading edge of the tile by a distance that is less than 150 mm.
7. The roof tile of any preceding claim wherein the tile is a tile having a specific secondary purpose, such as a ventilation tile, or soil stack terminal.
8. A tiled pitched roof including a plurality of roof tiles and having a plane that extends from an eave of the roof to a ridge of the roof and meets the upper surface of the tiles in the roof, each tile having a curved upper surface that extends between leading and trailing edges, the upper surface and the leading edge being visible, wherein a curvature of the upper surface of the tiles is such that a junction between the leading edge and the upper surface of each tile lies below the plane.
9. The tiled pitched roof of Claim 8, where the roof tiles are roof tiles according to any of Claims ito 7.
10. A roof tile substantially as hereinbefore described with reference to Figures 7 to 11, 15a and 15b of the accompanying drawings.
11. A tiled pitched roof substantially as hereinbefore described with reference to Figures 15a and 15b of the accompanying drawings.