GB2512366A

GB2512366A - A roof covering and a method for manufacturing a roof covering

Info

Publication number: GB2512366A
Application number: GB1305685.8A
Authority: GB
Inventors: Daniel Stuart Jarman; Jeremy Paul Lecornu
Original assignee: Hydro International Ltd
Current assignee: Hydro International Ltd
Priority date: 2013-03-28
Filing date: 2013-03-28
Publication date: 2014-10-01
Also published as: GB201305685D0

Abstract

The roof covering comprises a first porous, permeable portion 8 and a second, impermeable portion 10. In use the first portion forms an upper surface 4 and the second portion a lower surface 4 with respect to an underlying roof structure. The first portion is arranged to absorb and retain rainwater whilst the second prevents water passing through to the underlying roof. The portions may be formed from a ceramic, such as clay, or from aerated concrete. The first and second portions may be substantially the same thickness. Pores 9 in the first portion may be formed by the burning-off of a pore forming, organic, low ash medium such as flour. The porosity of the first portion is configured to increase the surface area for the evaporation rate of retained water. Heating of the first portion may form part of a firing process that hardens the first and second portions.

Description

A ROOF COVERING AND A METHOD FOR MANUFACTURING A ROOF

COVERING

The present invention relates to a roof covering which has a porous layer and to a method for manufacturing such a roof covering.

Background

In recent years, flash flooding after sudden rain has become more common as a result of increased urbanisation. In particular, the replacement of natural vegetation with manmade impermeable materials, such as concrete and tarmac, reduces the ability of soil to absorb rainwater. Consequently, rather than being absorbed, rainwater is instead directed into surface water drainage systems. The increased surface runoff caused by urbanisation (known as urban runoff) places surface water drainage systems under considerably more demand, which can result in the drainage systems becoming overloaded and can cause flooding (particularly flash flooding).

To counteract the effects of urbanisation, Sustainable Urban Drainage Systems (SUDS) or Low Impact Development (LID) techniques can be used. These are designed to reduce the potential impact of new and existing developments with respect to surface water drainage discharges. Their key objective is to manage the flow rate and volume of surface runoff to reduce the risk of flooding and water pollution. They can also reduce demand on the sewerage network and can improve biodiversity and local amenity.

Regulatory agencies are tasked with developing policy and regulations that limit runoff into storm sewers. A common objective in sustainable flood management is to infiltrate or intercept the first few millimetres of rainfall. The reason being is that the first few millimetres of each rainfall event accounts for the majority of the annual rainfall volume.

Therefore effectively managing this volume will significantly reduce the overall flood risk.

The initial runoff could be intercepted using traditional infiltration systems. However, such systems cannot be applied everywhere and it is believed that infiltration rates are too low in certain areas for this method of disposal to be practical.

For large urbanised areas the roof area of structures represents a significant proportion of runoff generation as they are usually impervious. They are, however, significantly underutilised for improving flood resilience. Currently only green or blue roof systems utilise the roof area with the objective of reducing flood risk, but these interception methods are often incompatible with typical construction methods and existing structures.

Accordingly, it is desirable to provide a roof covering which aids in reducing flood risk and which complies with traditional building approaches and techniques.

In accordance with a first aspect of the invention there is provided a root covering comprising: a first portion which is porous and permeable; and a second portion connected to and lying against the first portion, second portion being impermeable; wherein, in use, the first portion is an upper portion and the second portion is a lower portion with respect to an underlying roof structure such that the first portion is arranged to absorb and retain rainwater and the second portion is arranged to prevent the retained rainfall from passing through the roof covering to the underlying roof structure.

The first and second portions may be formed from the same material. Alternatively, the first and second portions may be formed from different materials.

The first and second portions need not be discrete portions and may be formed from an anisotropic material which has properties that differ through the thickness of the material in order to produce a porous region and an impermeable region.

The first portion may be formed from a porous material and the second portion may be formed from an impermeable material. On the other hand, the first portion may be formed from an impermeable material which is made porous.

The first and/or second portions may be formed from ceramic. The ceramic may be clay.

The first and/or second portions are formed from concrete. The first portion may be formed from aerated concrete, providing the required porous character.

The first portion may have an average pore size (diameter) of between 30 and 70 microns, and preferably an average pore size of substantially 50 microns.

The first and second portions may have substantially the same thickness.

Alternatively, the first and second portions may have different thicknesses. For example, the first portion may be significantly thicker in order to absorb and retain a large volume of rainwater.

The first portion may comprise pores formed from burning off a pore forming media located within the first portion.

The pore forming media may be an organic, low ash media, such as flour, particularly olive stone flour.

The porosity of the first portion may be configured to increase surface area so as to enhance the evaporation-rate of the retained rainwater.

The first and second portions may be first and second layers.

The roof covering may be a roof tile.

In accordance with another aspect of the invention there is provided a method for manufacturing a roof covering comprising: forming a first portion which is porous; and forming a second portion which is connected to and lying against the first portion, the second portion being impermeable; wherein, in use, the first portion is an upper portion and the second portion is a lower portion with respect to an underlying roof structure such that the first portion is arranged to absorb and retain rainwater and the second portion is arranged to prevent the retained rainfall from passing through the roof covering to the underlying roof structure.

Forming a first portion which is porous may comprise: forming the first portion from a non-porous material; and creating pores within the non-porous material.

Creating pores in the non-porous material may comprise: adding a pore forming media to the non-porous material; and heating the first portion to burn off the pore forming media, thereby creating pores within the non-porous material.

The pore forming media may be an organic, low ash media.

Heating the first portion may form part of a firing process. The firing process may harden the first and/or second portions.

The first and second portions may be first and second layers.

The roof covering is visually similar to conventional tiles and is laid using standard practices. The roof covering may therefore be retrofit to existing structures and is likely to be readily adopted by both tradesmen and end customers.

Brief Description of the Drawings

For a better understanding of the present disclosure, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-Figure 1 is a perspective view of a roof tile according to an embodiment on the invention; Figure 2 is a cross-section through the roof tile of Figure 1 along the line A-A; Figure 3 is an enlarged cross-sectional view of the roof tile prior to a firing process; Figure 4 is an enlarged cross-sectional view of the roof tile after the firing process.

Detailed Description

With reference to Figure 1, a roof tile 2 according to an embodiment of the invention is shown. The roof tile 2 resembles a traditional roof tile and has a substantially rectangular cuboid shape with a substantially planar profile.

The root tile 2 comprises an upper surface 4 and a lower surface 6. In use, the lower surface 6 is arranged to be adjacent to an underlying roof structure and the upper surface 4 is spaced from the underlying roof structure such that it is exposed to the environment.

A plurality of roof tiles 2 may be used to cover a building in a conventional manner. For example, the roof tiles 2 may be applied to an underlying roof structure by affixing (e.g. nailing) a plurality of root tiles 2 to a batten extending across the width of the root to form a course of tiles. The roof tiles 2 may be provided with one or more protrusions (not shown) which project perpendicularly from the lower surface 6 at a position which is towards one side of the roof tile 2. Such protrusions may be used to hook the roof tiles 2 to the batten.

A plurality of courses are arranged on the roof in an overlapping manner, with the tiles of adjacent courses offset from one another so as to prevent ingress of water through the roof. Many tiling methods are known with which the roof tile 2 of the present invention can be used.

The construction of the roof tile 2 will now be described with reference to Figure 2 which shows a cross section through the roof tile 2.

As shown, the roof tile 2 is formed of a first layer 8 and a second layer 10. The first and second layers 8, 10 are both planar sheets of substantially the same thickness which are laid one on top of the other and connected to one another to form the roof tile 2.

In use, the roof tile 2 is arranged on the roof such that the first layer 8 is an upper layer and the second layer is a lower layer 10. Accordingly, the first layer 8 comprises the upper surface 4 and the second layer comprises the lower surface 6. The second layer is therefore disposed adjacent the underlying roof structure, whereas the first layer 8 is spaced from the roof structure and is exposed to the environment.

The second layer 10 is formed from a material which is substantially impermeable to water. Consequently, water is unable to pass through the second layer 10. In contrast, the first layer 8 is porous and permeable, and is therefore able to absorb and retain water. The first layer 8 comprises pores 9 which have an average pore size (diameter) of between 30 and 70 microns, and preferably substantially 50 microns.

Both the first and second layers 8. 10 are formed from a ceramic, such as clay.

However, the first layer 8 is treated to provide a porous structure, as will be described further below.

In a storm, rainwater falls on the upper surface 4 of the roof tile 2. The rainwater is absorbed by the porous structure of the first layer 8. However, the second layer is impermeable to water, as described above, and thus prevents water from passing entirely through the roof tile 2 and out of the lower surface 6. The roof tile 2 is therefore able to absorb rainwater without compromising the ability of the roof tile 2 to prevent the ingress of rainwater through the roof. Consequently, the first layer 8 absorbs and retains rainwater and thus provides a porous storage medium for rainwater.

The porosity of the upper surface 4 is configured to increase the surface area of the roof tile 2. This enhances the evaporation-rate of the retained rainwater within the first layer 8. This therefore provides the additional benefit of reducing the total volume of rainwater continuing from the roofing surface, thus further reducing the risk of flooding in developed areas. The evaporation of rainwater also acts to reduce urban heat island effects, which improves air and surface water quality in the local area.

Testing of the roof tile 2 has shown that it is able to absorb and retain at least the first 5 millimetres of a rainfall event.

As described, the roof tile 2 reduces the continuation volume of rainwater passing over the surface of the roof tile 2. Consequently, less rainwater is passed from the roof to local drainage systems, helping to alleviate the burden placed on such systems and avoiding flooding.

A method for manufacturing the roof tile 2 in accordance with another aspect of the invention will now be described with reference to Figures 3 and 4.

As described above, the roof tile 2 comprises the first layer 8 and the second layer 10.

The first and second layers 8, 10 are preferably formed of clay. As shown in Figure 3, the first layer 8 is formed from clay which is mixed with particles of an organic, low ash media 11. The media 11 may be flour, such as olive stone flour, having an average particle size which corresponds to the desired pore size. The second layer 10 is formed from standard impermeable clay.

The first and second layers 8, 10 are laid one on top of the other and are fired in a single firing process to permanently harden the first and second layers 8, 10 to form the roof tile 2. The firing process may be performed in a kiln in a conventional manner or using any other conventional technique.

Figure 4 shows the roof tile 2 following the firing process. As shown, the firing of the clay causes the media 11 to "burn off' from the first layer 8, leaving behind the pores 9.

Accordingly, the porous structure of the first layer 8 is created in a simple manner without requiring any additional complicated manufacturing steps.

The roof tile 2 has been described and shown as having first and second layers 8, 10 which are of substantially the same thickness. However, the relative thicknesses of the first and second layers 8, 10 may vary depending on the desired performance characteristics. For example, the thickness of the first layer 8 may be increased in order to retain a larger volume of rainwater, provided that the second layer 10 is still sufficiently thick to prevent ingress of rainwater and that the roof tile 2 is sufficiently structurally robust.

Although the roof tile 2 has been described as having first and second layers, they need not be discrete portions. For example, the roof tile may be formed from an anisotropic material which has properties that differ through the thickness of the material in order to produce a porous region and an impermeable region. Accordingly, where the first and second layers are described as being connected, this does not necessarily require or imply any active fixation or connection of the two layers.

The roof tile 2 has been described as being formed from a ceramic material, such as clay; however, other materials may be used. For example, the roof tile 2 may be formed from concrete, with aerated concrete (similar to that used in lightweight concrete blocks, known as "breeze blocks") being used for the upper first layer 8. It may also be possible to construct the roof tile 2 from a suitable polymer.

Although the roof tile 2 has been described and shown as a substantially planar rectangular cuboid, other profiles and shapes may be used. Furthermore, the two-layer construction of the tile may be applied in other roof coverings. For example, the two-layer construction may be supplied in sheet form.

Claims

Claims 1. A roof covering comprising: a first portion which is porous and permeable; and a second portion connected to and lying against the first portion, the second porlion being impermeable; wherein, in use, the first portion is an upper portion and the second portion is a lower portion with respect to an underlying roof structure such that the first portion is arranged to absorb and retain rainwater and the second portion is arranged to prevent the retained rainfall from passing through the roof covering to the underlying roof structure.
2. A roof covering as claimed in claim 1, wherein the first and second portions are formed from the same material.
3. A roof covering as claimed in claim 1, wherein the first and second portions are formed from different materials.
4. A roof covering as claimed in any preceding claim, wherein the first portion is formed from a porous material and wherein the second portion is formed from an impermeable material.
5. A roof covering as claimed in any preceding claim, wherein the first and/or second portions are formed from ceramic.
6. A roof covering as claimed in claim 5, wherein the ceramic is clay.
7. A roof covering as claimed in any preceding claim, wherein the first and/or second portions are formed from concrete.
8. A roof covering as claimed in any preceding claim, wherein the first portion is formed from aerated concrete.
9. A roof covering as claimed in any preceding claim, wherein the first portion has an average pore size of between 30 and 70 microns.
10. A roof covering as claimed in claim 9, wherein the first portion has an average pore size of substantially 50 microns.
11. A roof covering as claimed in any preceding claim, wherein the first and second portions have substantially the same thickness.
12. A root covering as claimed in any preceding claim, wherein the first portion comprises pores formed from burning off a pore forming media located within the first portion.
13. A root covering as claimed in claim 12, wherein the pore forming media is an organic, low ash media.
14. A roof covering as claimed in claim 12 or 13, wherein the pore forming media is flour.
15. A roof covering as claimed in any preceding claim, wherein the porosity of the first portion is configured to increase surface area so as to enhance the evaporation-rate of the retained rainwater.
16. A roof covering as claimed in any preceding claim, wherein the first portion and the second portion are first and second layers.
17. A roof covering as claimed in any preceding claim, wherein the roof covering is a roof tile.
18. A roof covering substantially as described herein with reference to and as shown in the accompanying drawings.
19. A method for manufacturing a roof covering comprising: forming a first portion which is porous and permeable; and forming a second portion which is connected to and lying against the first portion, the second portion being impermeable; wherein, in use, the first portion is an upper portion and the second portion is a lower portion with respect to an underlying roof structure such that the first portion is arranged to absorb and retain rainwater and the second portion is arranged to prevent the retained rainfall from passing through the roof covering to the underlying roof structure.
20. A method as claimed in claim 19, wherein forming a first portion which is porous comprises: forming the first portion from a non-porous material; and creating pores within the non-porous material.
21. A method as claimed in claim 20, wherein creating pores in the non-porous material comprises: adding a pore forming media to the non-porous material; and heating the first portion to burn off the pore forming media, thereby creating pores within the non-porous material.
22. A method as claimed in claim 21, wherein the pore forming media is an organic, low ash media.
23. A method as claimed in claim 21 or 22, wherein heating the first portion forms pad of a firing process.
24. A method as claimed in claim 23, wherein the firing process hardens the first and second portions.
25. A method as claimed in any of claims 19 to 24, wherein the first and second portions are first and second layers.
26. A method for manufacturing a roof covering substantially as described herein.