A backing sheet

Abstract

Backing sheet K for supporting slates SL, SM on a roof structure R and comprising a flexible body with a curved or non-linear profile, a plurality of sealing strips T extending longitudinally from an

Description

Field The present invention relates to roof coverings and more particularly backing materials or backing sheets which are placed between an underside of a roof slate and a batten. Background Roofing slates have a unigue appearance that is a common aspect in roofing throughout the world. Recent changes to construction regulations reguire many buildings to properly ensure that they have increased levels of fire resistance and fire safety. Additionally, modern architectural building designs also utilise roof types that are beyond the normal waterproofing capabilities of traditionally installed roofing slates. Roofing slates are thinly split rectangular pieces of stone that are uniformly shaped so that the height of the slate is often twice the width of the slate. Slate is a natural product, and contrary to popular belief are not completely flat. Typically slates have surface undulations and protuberances. When roofing slates are cut to size, they are usually manufactured with two holes positioned either side of the slate, approximately one tenth of the slate width from an edge and typically around three fifths of the slate width from the bottom of the slate. The position of these holes defines the installation parameters of the slate. So that the lower two fifths of a slate, when fitted, are permanently visible and exposed to the elements. This part of the slate is known as the surface margin. The middle one fifth section of the slate is known as the lap and the upper two fifths of the slate, usually above the nail holes when the slate is fitted, is known as the holing margin. Natural roofing slates are traditionally installed on uniform lateral timber members that are fixed laterally across a timber roofing frame which forms a triangular tent like roof structure of a building. These laterally installed timber strips are known as battens and are spaced eguidistant up a roof structure in courses. These courses are dimensioned to coincide with position of the fixing holes in the upper two fifths of the roofing slate. The eguidistant spacing of these battens is often referred to as the batten gauge. When installed slates are arranged in rows along each course. Adjacent slates abut one other with an open perpendicular joint or perp when installed side by side and fixed directly onto the battens. Progressing from a lower part of a roof and consequently when moving from one course to the next, or subsequent, course of slates to be installed, slates are installed directly and centrally over an open abutment joint of a row of slates below so that three fifths of the perp joint below is covered by the slate installed above it. This method is known as broken bond installation. The broken bond method requires that effectively half of the slate in a row above sits longitudinally along half of the slate below. The measurement of cover is half the width of the slate and is known as the bond. The method is repeated for a third (and each subsequent) course so that slates are installed over two thirds of the perp join below but also, the third slate directly overlaps the first slate by one fifth the length of the slate. This method of roofing is known as double lap roofing where slates are layered so that open perp joints are covered by the slates above thereby creating a weatherproof roof covering. The double lap method of slate roofing relies on the angle or pitch of the inclined roof. A steeper pitch tends to expel rainwater from the roof surface more efficiently and prevents the water from permeating through the open perp joints and entering into and between the layers of the slates. When slates are installed at a lower roof pitch, any water that has passed through an open perp is drawn between the layers of slates by air pressure differentials and when this occurs water travel across the bond of the slates. In normal condition, this creeping of water between the layers should never be allowed to reach a point that is higher than a top of the first slate. If this occurs, then the roof will leak at either a nail fixing hole or at the critical junction where the mid-point at the top of the first slate is open at the mid-point of the second perp joint that is ultimately covered by the lower fifth or lap of the third upper slate. It has long since been established that this this open method of layering slates requires the roof to have a minimum roof pitch at which the roof covering will remain weatherproof. In addition, this open method of layering the slates permits air to flow between the layers and should a fire occur within the building then the free flow of air will act to accelerate this by providing an updraught. Slates are commonly fixed directly to the roofing battens using non-ferrous nails. When slates are installed at the lower roof pitch, they are more susceptible to air pressure forces and can suffer from wind uplift or slate chattel whereby stronger winds can cause the slates to rattle. Should this happen, then the slates are more prone to fracturing and this can also be detrimental to the integrity of the roof. Slate holes are also a point of ingress for water which can creep across the slate, especially at a lower pitch. Should water reach the fixing points then this water can find its way downwards along the shaft of the nail, through the hole in the slate and saturate timber battens around the nail fixing. Allowing the battens to get wet around the fixings in this manner, causes rotted in the timber and in turn can lead to loosening of the purchase of the nail and so considerably shorten the life span of the roof. Roofing slates are a traditional and longstanding method of forming a durable and aesthetically pleasing roof covering. Slates are made from quarried stone that is split into thin rectangular plates that conform to several varied, yet traditional requirements of size and shape, for example an extremely popular size has an area of 500 mm x 250 mm and is typically split to a thickness between 5 mm and 7mm. It is appreciated however that there are many variations in sizes, but all tiles share the same principle and are installed in the same manner. Natural slates are mounted upon timber strips known as roofing battens that are thus mechanically fixed laterally (usually nailed) in an opposite direction on to the timber rafters. These rafters are used to form the roof structure. A membrane known as a tile underlay is laid on top of the rafters and underneath the battens to form a secondary weather barrier. The whole structure can thus be an arrangement that forms the roof of a building. In order to install slates on the roof frames an installer should first apply a secondary waterproofing membrane layer known as an underlay that is laid over the rafters. On top of this underlay, strips of wood known as roofing battens are fixed in a horizontal position laterally over the underlay and across the roofing frames or rafters. These battens are spaced parallel and approximately 2 / 5th the length of the slate and cover the whole of the roof. In order to lay slates, they are placed lengthways on the battens, adjacent each other, and thereby form the first course or row of slates. The abutment joint of these slates is known as the perp that being a perpendicular or vertical join that remains visible upon the roof. This perp join can be closed or open with the gap ranging from 0 mm to 5 mm in width. Perp joins are not sealed or waterproof and will allow rainwater to pass through them and land on the slate below. On completion of the first row the second row can now be installed. The length of the slate means that approximately 3 / 5ths of this second row of slates covers the slates on the first row that is positioned below. The covered 3 / 5th section of slate is called the holing margin and this arrangement is known as the primary lap. The slates on the second row are positioned so that the perp join is placed over the centre point of the slate on the first row that is below. The centre of the slate above is covering the upper part of the perp join below in an arrangement known as broken bond. The central positioning of this perp join establishes the bond of the slate below, that usually being half the width of a slate. On completion of the second row the third row is installed similarly in a broken bond with slates in the second row directly below them. The slates on the third row are positioned directly above and in line with the slates on the first row. The third row will also overlap the first row by some 1 / 5th and this is known as the secondary lap. The complete arrangement of slates is known as double lap roofing. As the slates are installed on top of the slate below then the lower 2 / 5 of that slate is and remains exposed to the elements and forms the visible part of the slate roof. This exposed area of slate is called the slate margin. The arrangement of these slates continues up the roof until the roof is fully covered in the slates. Slates are laid in a double lap format using slates of many differing sizes and gauges. The slate width decides the bond of the slate. The bond used in conjunction with an appropriate lap will determine the weather resistance of a roof at a given roof pitch. When rain falls onto the roof gravity will force it down the slope running over the slates. This water first starts to penetrate the layers of the slates when it leaves the slate above and enters the perp join at the critical junction. The water flows through the perp join, landing on the holing margin of the slate below. This water creeps sideways from this perp join, underneath the margin section of the slates on either side, whilst on top of the holing gauge of the slate below. This water eventually exits at the tail portion of the slate back onto the surface of the roof. When the roof pitch is too low, gravity effects are weaker, and water can creep further across the holing margin of the slate until it reaches either a nail hole or the point of ingress. With the addition of a little air pressure (such as a strong breeze or wind), and if the gap between the slates is below 0.5 mm, then capillary action can draw water even further across the slates. This action can also draw water vertically through the lap at the tail of slate and thus over the head or top part of a slate causing a leak through the perp at the point of ingress. The risk of a leak is reduced if the bond is wider because the water has further to creep across the slate when it passes through the layers before it can reach the points of ingress. If the slates are pre-holed for nails, then these holes are closer than the critical junction and will pose a further risk. In higher wind conditions the water can be held onto the roof or even driven up the roof. This creates greater pressures and will increase the capillary action, forcing the water up and between the laps of the slates. The shorter the lap, the higher the risk and thus it is important that the length of this lap is increased. Water ingress through the slates falls onto the underlay and is directed to run under the battens and leave the roof via an eaves tray. However, continued leaking through the slates cannot be allowed because it will saturate the battens and corrode the nails and it is batten and nail rot that is a major cause of roof failures. Further, water ingress on to sagging underlay can result in the water pooling on the underlay and then overflowing into adjacent areas. This can result in water pooling on further underlay areas on the roof and / or result in water entering gaps or tears in the roof. This type of water damage can eventually lead to roof failure by saturating the battens and corroding the nails. Prior Art UK patent application number GB 2 526 553 (Makin) addresses the problem by providing a roll-formed plate that is placed between slates in a slated roof that inhibits water ingress through the roof. United States patent US 5 457 924 (Fujii, Keizou et al) relates to a slate roofing material joint having a flat strip-shaped mounting base plate made of weatherproof soft resin. The entire structure forms an integral unit made of weatherproof soft and hard resins for carrying away water which have may have seeped through the roofing material. Japanese patent application JP S60 129351 (Maizuru KK) discloses a structure of a roof tile, particularly a roof tile suitable for a ceramic tile. Conventionally, there are various types of roof tiles, such as Japanese type and pear, all of which are relatively small, and each tile is roofed in a valley with a partly overlapped front and back, left and right portion. German Offenlegungschrift DE 20101635 (Mage Herzberg GmbH) discloses a splice for a beaver roof which is a pitched roof covered with so-called beaver tiles. These are typically flat, plate-shaped rooftiles that usually have a rounded edge on one side. United States patent US 1 709 376 (Shirley) discloses a spacing device for a roof covering known as a shingle. International patent application WO 94 / 24384 (Waddington) discloses an improved tile roofing system for securing together flat shingles / tiles which can be glass, ceramic, slate, timber, plastic, cement or terracotta. Extreme weather conditions are rare, but are becoming increasingly common. Currently it is normal practice to allow a slight ingress of water through the slates because a roof space soon tends to dry. However, the battens should never be persistently saturated. Accordingly, there is the need for something that is able to inhibit such water ingress through the roof covering. An object of the invention is to reduce the risk of flames spreading. It is an object of the invention to reduce water ingress through the slates onto the underlay. It is another object of the invention to prevent saturation of wooden battens and so avoid nails corroding to reduce the risk of roof failure. Summary of the invention According to a first aspect of the invention, there is a backing sheet for supporting slates on a roof structure, comprising: a flexible body that in use has a non-linear profile, a plurality of sealing strips extending longitudinally from an upper region to a lower region of the body; and a connector for attaching the backing sheet to the roof structure, wherein when a slate is placed on the backing sheet the flexible body conforms to adjust its non-linear profile so that at least one of the sealing strips is in continuous contact with an underside of the slate. In some embodiments the flexible body prior to deployment is curved. Preferably the flexible body is curved with a radius of curvature whose vertex is within the roof structure. The backing sheet comprises a waterproof polymer sheet, such as for example a glass reinforced plastic (GRP). The present invention provides an improved backing sheet that provides additional sealing portions for improved waterproofing, is non-rigid, and has a non-linear profile before and after deployment, making it adaptable to provide improved functionality with non-uniform shapes of slate. The backing sheet can be manufactured by known means and to a length of 25cm to 50cm and a width of 10cm to 20cm. The connector is preferably in the form of an “S” shaped bend that is located on an end of the body of the backing sheet. In other embodiments, the connector is curved at an acute angle so as to form a suitable means to attach to the roof structure, such as the batten of the roof. Preferably, the flexible body prior to deployment is curved. Preferably, the flexible body is curved with a radius of curvature whose vertex is within the roof structure. The present invention addresses the technical problem of waterproofing in roofs by providing a backing sheet that comprises a body that has a non-linear profile before deployment and in use. This results in the body of the backing sheet adapting its shape to form continuous physical contact with, for example, slate, even with environmental effects such a strong wind or taking into account non-planar regions in the slate. This is achieved through the continuous physical contact between the body of the backing sheet and the slates, which stops capillary action that otherwise causes water to ingress through gaps between the slates, and through nail or drill holes made by attaching slates to the roof. The present invention provides the technical advantage of being adaptable to shape itself or conform to different slates or other suitable roof material while in use. The shape of the body is, for example, adapted by curving, or in some embodiments, by adapting a wavy, sinusoidal pattern on a corrugated roof. Preferably, the backing sheet comprises a waterproof polymer sheet. In a preferred embodiment, the backing sheet comprises a glass reinforced plastic (GRP). GRP is the preferred material as it provides a tough material with a high strength-to weight ratio, while being versatile to be non-rigid and being producible to be fire resistant and / or coated with a fire retardant material. However, other suitable materials can be used instead of GRP. These can include carbon, basalt or aramid polymers. In a preferred embodiment, the backing sheet is fire resistant. A technical advantage of the present invention is that it can be made to be fire resistant up to a class 0 or (B-S1, dO) standard. Preferably, the plurality of sealing strips comprises a resiliently compressible foam. In some embodiments there can be two or more sealing strips. The number of sealing strips on the backing sheet can be selected depending on the width of the body of the backing sheet and the roofing material that is to be secured to the backing sheet. Preferably, the sealing strips comprise a resiliently compressible foam that provides the technical advantage of being durable to withstand the weight of the roof material that is to be secured to the roof, while also preventing the material from sliding off of the backing sheet while being fitted to the roof. In a preferred embodiment, the resiliently compressible foam comprises ethylene propylene diene monomer (EPDM) or neoprene (RTM). This material provides the technical advantage of being durable, fire resistant and weather resistant. However, other suitable material, such as other rubbers or elastomers, can be used which provides these advantages. Preferably, the sealing strips are positioned on the body of the backing sheet to align with user made holes in a slate resting thereon and the sealing strips are dimensioned to form a seal around a fastener which attached the slate to the roof structure. This provides the technical advantage of providing additional waterproofing against the capillary action from liquid on the roof caused by rain or other sources. The sealing strips can be placed on or near the periphery of the body of the backing sheet, or in the centre of the body of the backing sheet. Preferably, the backing sheet is used on a portion of the slate abutment of the roof. This provides the technical advantage of the backing sheet being sized to be versatile in providing waterproofing in areas where a slate roof meets a wall or other vertical structure. Preferably, there is a kit of parts comprising the backing sheet, a plurality of slates and a plurality of attachment means, such as nails. Preferred embodiments of the invention will now be described, by way of example and with reference to the Figures in which: Brief Description of the Drawings Figure 1 shows the embodiment of the backing sheet from a first perspective and second perspective showing the non-linear profile of the body of the backing sheet; Figure 2 shows a perspective of a slated roof depicting multiple backing sheets according to the first aspect of the invention that are underlying the slates; Figure 3 shows the embodiment of the backing sheet from Figure 1 from a perspective showing the backing sheet attached to the roof and showing the non-linear profile of the body of the backing sheet in use. Detailed Description of Preferred Embodiments of the invention Referring to Figures 1 to 3, in a preferred embodiment, the backing sheet (K) comprises an elongated sheet of glass reinforced plastic (GRP) polymer that has a flexible, curved body (C). In a preferred embodiment, the backing sheet (K) has a length of approximately 25 cm and a width (¢) of approximately 10 cm. However, in some embodiments the length may exceed 30 cm and the width of the backing sheet is between 7 cm and 10 cm. The backing sheet (K) is manufactured by known means. The backing sheet (K) comprises a first and second sealing strip (tape) of resiliently compressible foam (T) comprising ethylene propylene diene monomer (EPDM), that extends longitudinally from the first end of the backing sheet (K) to the second end. The first and second sealing strips (T) are positioned near the periphery of the body of the backing sheet (K) to receive a nail (NA) or other fastener that will be passed through the slate (SL) when placed on the backing sheet (K) and secured to the roof (R). On the first end of the backing sheet (K) there is a connector (B) that has a shaped profile which is angled away from the body of the backing sheet (K). The connector (B) is used to place the backing sheet (K) onto a batten of the roof (R) structure (BA), which will hold the backing sheet (K) in place as slate (SL) is being secured to the roof (R). As shown in Figures 2 and 3, before deployment, the backing sheet (K) has a curved profile (C) that can further curve or bend in use as shown in Figure 3; while maintaining a radius of curvature whose vertex is within the roof structure. As shown in Figure 3, in use, the backing sheet (K) is attached to the batten of the roof (BA) through the shaped connector (B). A slate (SL) is then placed at the desired location on at least one sealing strip (T) on the backing strip (K). The slate (SL) is then nailed (NA) to the roof (R) through the backing strip (K), securing the slate (SL) in place. The sealing strips (T) form a seal around the nail (NA) and user-made hole in the slate (SL) to prevent water ingress through the slate (SL). Advantageously, multiple backing strips (K) can be used when securing slate (SL) to a roof structure. As shown in Figure 2, multiple backing strips (K) can be used when overlapping slate (SL) on the roof structure. This further improves the waterproofing of the secured slate (SL) on the roof (R). During heavy rain, heavy wind or other adverse weather conditions that may move the slate (SL) on the roof (R), the body of the backing strip (K) will curve and bend in conjunction with the movement of the secured slate (SL). This results in the backing sheet (K) maintaining continuous contact with the secured slate (SL). The continuous contact removes the problem of capillary action that causes water to ingress through the user-made holes or other artefacts in the slate (SL), thereby preventing water ingress through the slates (SL) and onto the roof structure causing water damage. The open abutment joints or perps of the slates (SL) are the points of the roof covering where rainwater can permeate into the layers of slate (SL) and, at lower roof pitches are areas where the roof (R) starts to fail through leakage. The backing sheet (K), in effect, introduces a fourth additional layer to the slates (SL) by closing of the top section of the open perp joint that extends three fifths down from the top of the slate (SL) on each course, it is this area that is most vulnerable to a leak. In a preferred embodiment, the backing sheet (K) is made using glass reinforced polyester (GRP) or similar into a thin plate in the shape of an elongated L (or hockey stick), GRP is known to have excellent fire-resistant properties. The top of the backing sheet (K) has a small downwards protruding section in the form of a connector (B) that hooks over the top of the roofing batten (BA), the downward protruding section (B) is smaller than the overall height of the batten (BA) so that the backing sheet (K) is always seated directly down onto the upper surface and corner of the roofing batten (BA), the backing sheet (K) cannot sit proud of, or higher than, the upper surface of the batten (BA) but must be in direct contact. It is also appreciated that the backing sheet can be used with or without a downward facing hook B when being used in a fully boarded roof space where roofing battens are not used. The main body of the backing sheet (K) is a flat thin plate that incorporates a slight upwards curve (C) or arch that should be able to span freely from the upper part of the roofing batten (BA), across the batten void (BV) and onto and above the top section of the slate (SL) that has previously been installed below (LAB). Unlike metal, which can be bent to a permanent shape, GRP, once cured, retains its original shape even though it might be stressed into a permanently held position. The plate is manufactured with the benefit of a slight upwards curve (C), that, when considered alongside the characteristic of a retained structural memory can be used permanently and resiIiently help to span the batten void (BV), whilst at the same time using the retained tension in the compressed arch to maintain contact with the underside of the flat slate. The excellent thermal characteristics of GRP will resist distortion through extensive cycles of solar thermal warming and cooling whilst in position upon the roof (R). The backing sheet (K) is positioned centrally and directly below the abutment joint of the slates (SL) as they are placed onto the roof (R), the backing sheet (K) sits centrally below the upper section of the open perp that is created by the abutment of the two slates (PE) that are installed above it. By way of its position, directly below the open perp, the backing sheet (K) therefore prevents the passage of water through the perp joint and this improves the weather resistance of the slates (SL), especially in circumstances where the roof pitch (P1) is set below the normally recommended angle. The backing sheet (K) also restricts the free movement of air between the slates and in such will reduce wind up lift pressures on the roof covering and, because of the fire-resistant properties of GRP in conjunction with the restriction of the air flow it will reduce the spread of flame in the event of a building fire. Roofing slates (SL) are usually fixed to the roofing battens (B) using non-ferrous clout nails (NA) that utilise the holes in the slates (SL). The roofing slates (SL) are installed in the usual manner on top of the backing sheet (K), the nails (NA) pass through the slate (SL), then through the backing sheet (K) and into the roofing batten (B). The process is then repeated up the roof (R). However, the nails (NA) create a risk of water transmittance around the shaft of the nail (NA), where it passes through the slate (SL), through the backing sheet (K) and into the battens (B). The backing sheet (K) has two parallel strips (tape) (T) of EDPM, Neoprene (or similar) compressible foam that are firmly and resiliently adhered to the upper surface, foam tape such as this has excellent properties in its ability to self-seal around a nail (NA) when it is driven through it. The strips (T) elongate the full length of the upper surface so that, when finally positioned, each strip is in contact with the underside of the slate (SL) above. The tape (T) is sufficiently wide enough (TW) and positioned on the backing sheet so that it passes centrally below the nail holes (NH) in the slates (SL). The tape (T) is an important innovation because of its multiple functions. Because of the natural undulations in the slate, the tape (T) provides both a cushion and a seal to the underside of the slate (SL), this cushioning will help to eliminate the occurrence of slate chattel. Because the backing sheet (K) is manufactured with a slight, yet permanent but also deformable upwards curve (C), the contact between the tape (T) and the underside of the flat slate (SL) is maintained by way of the structure and integrity of the GRP against the rigid straightness of the slate (SL). The tape (T) will provide a compressed seal joint that will prevent the movement of water between the backing sheet (K) and the underside of the slate (SL), any water present in this area will therefore be tracked down the natural channel of the perp joint and be contained withing the inside channel that is created between the parallel lines of tape (T). The seal created by the tape (T) will further reduce the movement of air that might otherwise be permitted to pass through the undulations in the natural slate (SL). Because the tape (T) passes directly below the nail holes (NH) in the slates, the fixing nails (NA) will be driven both through tape (T) and also the GRP plate. The composition of the tape (T) is such that it provides an effective seal around any nail (NA) should it be drive through it and in such, the tape (T) prevents the risk of damage to the roof (R) through the transmittance of water around the fixings. The backing sheet (K) is installed directly prior to the installation of the slate (SL), because of the incline of the roof (R), it is advantageous for the backing sheet (K) to be easily positioned so that it does not slide down the roof (R) should it not be held in position, the downwards facing hook section (B) of the backing sheet (K) locates over the upper corner of the fixed roofing batten (BA) and as such, this prevents the backing sheet (K) from slipping down off the roof during installation, thus permitting the installer to have both hands free to better facilitate the installation of the roofing slates (SL). The hook (B) also allows for packs of the backing sheet (K) to be easily loaded onto the roofing battens (BA) prior to installation. The invention has been described by way of examples only and it will be appreciated that variation may be made to the above-mentioned embodiments without departing from the scope of invention as defined by the claims.

Claims

1) A backing sheet for supporting slates on a roof structure, comprising:a flexible body that in use has a non-linear profile,a plurality of sealing strips extending longitudinally from an upper region to a lower region of the body; anda connector for attaching the backing sheet to the roof structure, wherein when a slate is placed on the backing sheet the flexible body conforms to adjust its non-linear profile so that at least one of the sealing strips is in continuous contact with an underside of the slate.2) The backing sheet according to claim 1, wherein the flexible body prior to deployment is curved.3) The backing sheet according to claim 2, wherein the flexible body is curved with a radius of curvature whose vertex is within the roof structure.4) The backing sheet according to any preceding claim, wherein the backing sheet comprises a waterproof polymer sheet.5) The backing sheet according to any preceding claim, wherein the backing sheet comprises a glass reinforced plastic (GRP).6) The backing sheet according to claim 4 or 5, wherein the backing sheet is fire resistant.7) The backing sheet according to any preceding claim, wherein the plurality of sealing strips comprises a resiliently compressible foam.8) The backing sheet according to claim 7, wherein the resiliently compressible foam comprises ethylene propylene diene monomer (EPDM) or neoprene (RTM).9) The backing sheet according to any preceding claim, wherein the sealing strips are positioned on the body of the backing sheet to align with user made holes in a slate resting thereon and the sealing strips are dimensioned to form a seal around a fastener which attached the slate to the roof structure.10) The backing sheet according to any preceding claim, wherein the backing sheet is used on a portion of the slate abutment of the roof.11) A kit of parts comprising the backing sheet of any preceding claim, a plurality of slates and a plurality of attachment means, such as nails.

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