A roofing sheet assembly

Abstract

A clip (50) for attaching a roofing sheet (20a, 20b) onto an underlying support structure (2), comprising: a base (52) fixedly attachable to a sidewall of the support structure (2) such that, upon att

Description

Field The present application relates to a roofing sheet assembly, and in particular to a clip, a roofing sheet, and a method for forming the roofing sheet assembly. Background Roofing sheets, otherwise used also as cladding sheets, are cost-effective solutions for sheltering outdoor areas and outbuildings. In some applications, particularly greenhouses and conservatories, double-glazed roofing sheets are utilized to improve thermal insulation and thereby reduce energy loss. However, such an installation requires the use of expensive glazing bars to be mounted on top of an underlying support structure, such as a purlin, which significantly increases its weight, cost and complexity, carrying some risk to the installers. In more general applications, corrugated plastic or metal sheets are typically used which offer improved mechanical strength and durability. Furthermore, the troughs at the corrugated sheets facilitate effective rainwater drainage. Through many large predrilled holes distributed throughout the roofing sheets, they are directly secured to the top of the purlins by special capped screws. Specifically, the capped screws overlap the large predrilled holes to create seals that prevent rainwater from leaking therethrough. However, the seals offered by the capped screws can deteriorate and move off-centre over time and so they may require frequent maintenance or replacement. Moreover, the large predrilled holes formed at the roofing sheets may not perfectly align with the screws or the purlins, which undermines the quality of the installation. Critically, conventional installations require an installer to access the top of the purlins. For example, the installer will have to climb on top of every purlin to screw the roofing sheets or glazing bars onto their upper surfaces. Such practice not only puts additional stress on the purlins during installation but working at height also carries considerable risks, especially for inexperienced installers. Therefore, a roofing sheet assemblies that offer an efficient installation, without requiring large holes to be drilled in the roofing sheets, or the installer to access the top of the purlins, are highly desirable. Summary The present invention provides a specially designed clip for attaching a roofing sheet from below an underlying support structure. Specifically, the clip is arranged to be fixedly attached to a sidewall of the support structure, thereby dispensing with the need for large holes to be drilled in the roofing sheets, or requiring the installer to access the top of the purlins. In most embodiments, the clip may be fixedly attached to the sidewall of the support structure after the assembled roofing sheet has been laid at the desired position, thereby minimising the likelihood of misalignment, or risk to the installers. The present invention is also very suited for emergency dwellings to be erected in many areas of the world, following natural disasters, the installers requiring few erecting skills and only basic tools, readily available. According to a first aspect of the presently-claimed invention, there is provided a clip for attaching a roofing sheet onto an underlying support structure, comprising: a base fixedly attachable to a sidewall of the support structure such that, upon attaching the clip to the support structure, a first end of the base aligns with the support structure in a horizontal plane; and an anchor formed at a second end of the base, the anchor having side protrusions engageable with sidewalls in a channel of the roofing sheet for forming attachment therewith, wherein the anchor is arranged to rotate 90° about a vertical axis inside the channel of the roofing sheets to switch between a first orientation and a second orientation, wherein in the first orientation the side protrusions are separated from the channel, and in the second orientation, the side protrusions engage opposite sidewalls of the channel to form the attachment. The anchor may have a depth that is narrower than a slot opening formed by the sidewalls of the channels, such that in the first orientation it is insertable into the channel through the slot opening. The roofing sheet may form from any suitable material, for example metals such as steel and aluminium formed by a rolling process, as well as polymers such as polycarbonate, acrylic, polystyrene and polyvinyl chloride formed by a continuous extrusion process. The roofing sheet may comprise a single layer of material, or it may comprise plural layers in a glazed arrangement, e.g. double- or triple-glazed for improved insulation. The roofing sheet may comprise a channel having sidewalls that at least partially complements the cross-sectional profile of the side protrusions of the clip, such that once the attachment is formed therebetween, the side protrusions can be securely retained in the channel. The underlying support structure may be a purlin, a beam or any longitudinal member that supports the roofing sheet. The roofing sheet may be supported over the plurality of parallel support structures, and therefore, a clip may be provided on each, or every few, support structures for forming the attachment. Once attached, the channel of the roofing sheet extends perpendicularly to the support structure. In contrast to known fixtures that are fixed to the top of the purlins, the base of the clip may be fixedly attached to the sidewall of the support structure. In a preferred embodiment, the first end of the base comprises an orifice through which a fixture or a fastener, e.g. a nail or a screw, extends and fixedly attaches the clip to the support structure. In some other embodiments, the first end of the base may be arranged to adhere to the sidewall of the support structure by a suitable adhesive. Therefore, once attached, the first end of the base may align with the support structure in the horizontal plane, i.e. the first end of the base is provided at the side of the support structure. Such an arrangement may advantageously allow the installer to work from underneath the purlins when nailing or screwing in the clips, without the need to drill large holes in the roofing sheets, or the installers to climb on top of the purlins as required by known installations. The clip’s anchor and its side protrusions, provided towards the second end of the base, may extend at a level above the support structure. Specifically, upon attaching the clip to the support structure, the side protrusions sit proud of the support structure and extend in a direction parallel to the support structure. Such an arrangement may allow the clip’s side protrusions to fully engage with both sidewalls of the sheet’s channel above the support structure and thus forming a secure attachment, along the length of each sheet as necessary. Optionally, each side protrusion comprises a lobed end for engaging with the sidewalls in the channel of the roofing sheet. In other words, the free end of each of the side protrusions has a rounded cross-sectional profile to complement a corresponding cross-sectional profile of the channel. Optionally, the lobed end has a substantially constant radius of curvature in its cross-sectional profile complementing at least a part of the cross-sectional profile of the sidewalls in the channel of the roofing sheet. For example, the lobed end has a cross-sectional profile in the shape of a semi-circle. Optionally, the lobed end has a greater thickness than other parts of the side protrusion. That is, the lobed end is enlarged compared to the shaft of the side protrusion, to which the sidewalls of the channel may lock onto more securely. During installation, the roofing sheet may be placed in a predetermined position and / or orientation on top of the supporting structure before inserting the anchor of the clip, in the first orientation, through the slot opening into the channel. Thereafter the clip may be rotated about the vertical axis inside the channel to switch from the first orientation to the second orientation, which causes the side protrusions to engage opposite sidewalls of the channel and thereby forming the attachment. Finally, the clip may be fixedly attached to the sidewall of the support structure to secure the roofing sheet to the support structure, without the need for large holes to be drilled in the roofing sheets. Advantageously, once attached, the channel of the roofing sheet interlocks the anchor, thereby preventing the roofing sheet from unintentional detachment when there is a significant upward lifting force acting thereupon, e.g. under high wind. Furthermore, such an arrangement may allow the clip to be fixedly attached to the support structure after the roofing sheet has been placed in the desired position, thereby eliminating any misalignment that is often experienced in known installations. In a conventional roofing sheet arrangement, an outwardly facing edge of a roofing sheet usually overhangs the support structure, e.g. the eaves or drip-edge of a building, by at least 70mm, such that any rainwater collected thereon can be promptly drained to a gutter underneath for collection and use, for washing etc. Such a gutter is usually separately supported by gutter brackets fixedly attached to a wall, or the supporting structure, of the building. In the present invention, optionally, the clip comprises a support for supporting a gutter section, and wherein upon attaching the clip to the support structure, the gutter section outwardly extends from the support structure and beneath an edge of the roofing sheet, e.g. a drip-edge. In some embodiments, the clip that is fitted to a leading support structure, e.g. the outermost support structure, may comprise tapped holes at its sidewall to which a gutter section, or a bracket for supporting a gutter section, may attach. Thus in these embodiments, the support may refer to as a detachable bracket or a gutter section couplable to the clip. In some other embodiments, the clip that is fitted to a leading support structure may be integrally formed with a bracket for supporting a gutter section. In some other embodiments, the clip that is fitted to a leading support structure may be integrally formed with a gutter section. Advantageously, such an arrangement allows the roofing sheet and the gutter section to be attached to the support structure by the same clip, thereby significantly reducing the work required for the installation. Optionally, the base comprises a positioning ridge extending along its sidewall, wherein upon attaching the clip to the support structure the positioning ridge rests on a top surface of the support structure for aligning the clip with the support structure. More specifically, the positioning ridge may function as a guide where the installer may fixedly attach the clip once its positioning ridge abuts the top of the support structure, thereby guaranteeing the anchor of the clip to precisely extend at a predetermined height above the support structure. In some other embodiments, the positioning ridge may take other forms, such as raised dots. Advantageously, such an arrangement may ensure the elevation of the roofing sheet is consistent over a plurality of support structures. According to a second aspect of the presently-claimed invention, there is provided a roofing assembly, comprising the clip of the first aspect and a roofing sheet, wherein the roofing sheet is attached to the underlying support structure by the clip that is fixedly attached to a sidewall of the support structure, without the need for large holes to be drilled in the roofing sheets. Optionally, the roofing assembly comprises a plurality of adjoining roofing sheets, wherein at least one channel of one of the roofing sheets overlaps another channel from an adjoining roofing sheet, wherein both the said channel and the adjoining channel are attached together to the support structure by the clip, and additional clips as necessary along their length. According to a third aspect of the presently-claimed invention, there is provided a method of attaching a roofing sheet to a support structure by the clip of the first aspect, comprising the step of: inserting the anchor of the clip into the channel of the roofing sheet to form the attachment. Optionally, the method further comprises the step of: positioning the roofing sheet at a predetermined location on top of the support structure prior to the inserting; rotating the clip about the vertical axis after the inserting, as such the side protrusions of the anchor engage with the channel to form the attachment; and fixedly attaching the first end of the clip to the sidewall of the support structure. Optionally, the method further comprises the step of biasing the clip towards the sidewall of the support structure after the rotating, so as to cause the clip to slide along the channel to abut the sidewall prior to forming the attachment. Features from any one of the first to the third aspects of the present invention may be applicable to any other feature from the other aspects. Brief Description of the Drawings Certain embodiments of the presently-claimed invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure lisa truncated front view of a roofing assembly according to a first embodiment of the present invention; Figure 2 is a truncated side view of a roofing assembly of Figure 1; Figure 3 is a truncated perspective view of a roofing sheet for forming the roofing assembly as shown in Figures 1 and 2; Figures 4A to 4D are truncated side views illustrating various steps of forming the roofing assembly of Figure 1; Figure 5A is a truncated plan view of a roofing assembly of the first embodiment; Figure 5B is a truncated front section view of a joint comprising four adjoining roofing sheets of the first embodiment; Figure 6 is a side view of a clip according to a second embodiment of the present invention; Figure 7 is a side view of a clip according to a third embodiment of the present invention; Figure 8 is a truncated front view of a roofing assembly according to a fourth embodiment of the present invention; and Figure 9 is a truncated perspective view of a roofing sheet according to a fifth embodiment of the present invention. Detailed Description Figures 1 and 2 are respectively truncated front and side views of a roofing assembly 10 according to a first embodiment of the present invention. In the illustrated embodiment, the roofing assembly 10 comprises two substantially identical roofing sheets 20a, 20b overlaying across a pair of parallelly extending purlins 2, e.g. underlying support structures. The two roofing sheets 20a, 20b, adjoined widthwise, are jointly attached to each of the purlins 2 by a single T-shaped clip 50. In other embodiments, the roofing assembly may comprise any number of adjoining roofing sheets and clips as required to overlay the full length of the underlying purlins. In contrast to known installations, the clip 50 is configured to fixedly attach to a sidewall of the purlin 2 at its first end, or lower end. More specifically, the clip 50 comprises a base 52 having an orifice opened at its first end, through which a nail 4 extends to secure the clip to the sidewall of the purlin 2. The base 52 further comprises an anchor provided at its second end, or upper end. The anchor comprises two side protrusions 56 extending parallel to the purlin 2 each having a lobed end 58 for engaging sidewalls of a channel 24 at the roofing sheet 20. Thus, the clip 50 is generally a T-shaped member. As illustrated Figure 1, the curvature of the lobed end 58 has a substantially constant radius, which partially corresponds to a cross-section profile of the sidewalls of the channel 24, otherwise referred to as a second channel or an inner channel. The lobed end 58 forms the thickest part of the side protrusion 56. Specifically, the top of the lobed end 58 levels with the top surface of the side protrusion 56, whilst its bottom extends beneath the floor of the side protrusion 56 to increase its reach. Thus, the centre of each lobed end 58 is vertically offset from the centreline of the corresponding side protrusion 56. Such an arrangement enables the sidewalls of the second channel 24 to grip onto the side protrusions 26 more securely. Figure 3 is a truncated perspective view of the roofing sheet 20 for forming the roofing assembly. The roofing sheet 20 comprises a first channel 22 and a plurality of second channels 24 evenly distributed along the width of the roofing sheet 20. Specifically, the roofing sheet 20 comprises a floor 21 proximal to the purlin 2 when the roofing sheet 20 is attached, and the first and second channels 22, 24 each extends upwardly from the said floor 21. The first and second channels 22, 24 extend along the length of the roofing sheet and are parallel to each other. More specifically, the first channel 22 is positioned adjacent to a leading side edge 26a of the roofing sheet 20 and the opposite trailing side edge of the roofing sheet 20 is provided with a second channel 24. Referring back to the roofing assembly 10 of Figure 1, the leading side edge 26a of the roofing sheet 20a covers the trailing side edge 26b of a second roofing sheet 20b. More specifically, the first channel 22 or outer channel of the roofing sheet 20a is configured to completely overlap the second channel 24 or inner channel of the second roofing sheet 20b, thus allowing both the roofing sheet 20a and the second roofing sheet 20b to be secured on the purlin 2 by the same clip 50. In order to accommodate the second channel 24, the internal dimensions of the first channel 22 correspond to the external dimensions of second channels 24, i.e. the first channel 22 is sized slightly larger than the second channels 22, and the first and second channels 22, 24 have generally complementary cross-sectional profiles. By reference to their relative positions, the second roofing sheet 20b can be referred to as a leading roofing sheet and the roofing sheet 20a can be referred to as a trailing roofing sheet. Each of the first and second channels 22, 24 comprises a pair of opposing S-shaped sidewalls. More specifically, each of the S-shaped sidewalls comprises an upper curved section 30 and a lower curved section 32 in a reverse curve arrangement. The radii of the upper curved sections 30 are positioned inside the channels 22, 24, thus they bulge outwardly to form an enlarged cavity for accommodating and engaging the lobed ends 58 of the side protrusions 56, of clip 50. In contrast, the radii of the lower curved sections 32 are located outside the channels 22, 24 and therefore they cave inwardly to form a slot opening, or a neck, which retains the lobed ends of the side protrusions 56 within the cavity formed by the upper curved sections 30. The width of the said slot opening is equal to, or larger than, the depth of the clip 50, as such the anchor of the clip 50 can slide into the channels 22, 24 through the central slot opening. The upper curved sections 30 is shown having a greater radius of curvature than the corresponding lower curved sections 32. The radius of curvature of the lower curved sections 32 generally relates to the extent of the base 50, and therefore the elevation of the roofing sheets 20a, 20b. As shown in Figure 1, a comparatively small radius of curvature at the lower curved sections 32 reduces the profile of the channels at the roofing sheet. As shown in Figure 1, the bottom of the lobed ends 58 abuts and biases against the upper curved sections 30 of the second channel 24, which on their own are sufficient to retain the roofing sheet 20 in place. To enhance the security of the attachment, the second channels 24 are additionally provided with gripping rails 36 extending along their length. In the illustrated embodiment, the gripping rail 36 protrudes from the joint between the upper and lower curved sections 30, 32. The gripping rail 36 is curved upwardly along its length and has a cross-section profile complementing the curvature of the lobed ends 58 of the side protrusions 56. Specifically, the gipping rail 36 has the same radius of curvature as the upper curved section 30 and can be taken as a continuation of the upper curved section 30. The curved gripping rails 36 grip onto the corresponding lobed ends 58 to prevent them from accidental detachment, e.g. under high winds. The pair of the upper curved sections 30 of the first and second channels 22, 24 are joined by a planar top section 34. The top section 34 extends the width of the channel for accommodating the elongated anchor. Thus, when viewed along the length of the roofing sheet, the first and second channels 22,24 each resembles an Omega, Q. Being double overlap thickness together, the joined strength is greatly increased, thus resembling a glazing bar, not now necessary or required. In contrast to known installations, the clip 50 can be fixedly attached to the purlin 2 after the roofing sheet 20 is fitted in place, and therefore eliminates any misalignment. Figures 4A to 4D are truncated side views illustrating various steps of forming the roofing assembly 10. In Figure 4A, the roofing sheet 20a is positioned at a desired location above the purlin 2, with its first channel overlapping a second channel of the second roofing sheet 20b. For example, the installer may slide the roofing sheets 20a, 20b into position when standing under the purlin 2. Once the roofing sheets 20a, 20b are in place, the installer may put the clip 50 in a first orientation where its side protrusions 56 are parallel to the overlapped channels 22, 24, before aligning it with the central slot openings of both channels 22, 24. This allows the anchor of the clip 50 to slide through the slot openings and be inserted in the cavity of the channels 22, 24 as shown in Figure 4B. In Figure 4C, the clip 50 is rotated 90° about the vertical axis to convert into a second orientation, in which its side protrusions 56 extend parallel to the purlin 2, with their lobed ends abut the sidewalls of the second channel 24 to form an interference fit. The clip 50 is retained in the channels 22,24 by their slot openings, and is movable along the lengths of the channels 22,24 when forced. The installer may then push and slide the clip 50 along the channels 22,24 until the sidewalls of the clip 50 and the purlin 2 abut each other. Finally, the clip 50 can be nailed to the sidewall of the purlin 2 by a nail 4 through the orifice at the first end of its base 52 to form the attachment. Advantageously, the entire installation can be accomplished without needing the installer to climb on top of the purlin 2. Thus, such a method significantly increases the efficiency of the installation, whilst minimising the risks posed to the installer. In some other embodiments, the sidewalls of the channel may be attached to the clip by a snap attachment. For example, during installation the sidewalls of the channel may be biased away from each other so as to widen the slot opening, thereby allowing the channel to directly snap onto the clip to removably attach the roofing sheet onto the support structure. In these embodiments, the gripping arms as shown in Figure 1 may optionally be absent to facilitate the snap attachment. This way, the roofing sheet may be secured onto the clip after the clip has already been fixedly attached to a predetermined position at the support structure. In addition to joining roofing sheets 20a, 20b widthwise as shown in Figure 1, the roofing sheets of the present invention can also be jointed lengthwise as required. Figure 5A is a truncated plan view of a roofing assembly of the first embodiment where a leading edge 27a of a third roofing sheet 20c, overlaps the trailing edge 27b of the roofing sheet 20a. The third roofing sheet 20c is shown in dotted lines to improve the clarity of the illustration. By reference to their relative positions, the roofing sheet 20a can be referred to as a front roofing sheet and the third roofing sheet can be referred to as a rear roofing sheet. More specifically, the channels 22,24 are narrowed towards the trailing edge 27b of the roofing sheet 20a such that their external dimensions are matched with the internal dimensions of corresponding channels 22, 24 provided towards the leading edge 27a of the third roofing sheet 20c. Thus, the narrowed portions of the channels 22, 24 at the roofing sheet 20a can be completely overlapped by their corresponding channels 22, 24 at the third roofing sheet 20c. Such an arrangement provides a substantially seamless connection between the roofing sheet 20a and roofing sheet 20c, the narrowed portion of the sheet being part of the extrusion or forming process, whether plastic or metal is used. In the illustrated embodiment, the channels 22, 24 are tapered and so their widths are reduced gradually towards the trailing edge 27b of the roofing sheet 20a. The tapering can be achieved by the use of a suitable extrusion die. In some other embodiments, the channels 22, 24 may exhibit a step change in size reduction, e.g. one or both ends of each channel 22, 24 may be thinned out. Together, by the overlapped channels 22, 24, both the roofing sheet 20a and the third roofing sheet 20c can be supported by a single clip 50b. Since the clips 50b are fitted to the narrowed portion of the second channels 24, they are sized smaller than the other clips 50 in the roofing assembly. Specifically, the external dimensions of the clip 50b correspond to the internal dimensions of the narrowed ends of the second channels 24. Figure 5B is a truncated front section view of a joint comprising four adjoining roofing sheets 20a-20d along theirlengths. Specifically, a front leading roofing sheet 20b is joined lengthwise with a rear leading roofing sheet 20d, wherein the front leading roofing sheet 20b having the narrowed end of its second channel overlapped by a corresponding second channel of a rear leading roofing sheet 20d. Furthermore, a front trailing roofing sheet 20a is joined lengthwise with a rear trailing roofing sheet 20c, wherein the front trailing roofing sheet 20a having the narrowed end of its first channel overlapped by a corresponding first channel of a rear trailing roofing sheet 20c. Together, the first channels of the stacked front and rear trailing roofing sheets 20a, 20c overlap the second channels of the stacked front and rear trailing sheets 20b, 20d to form the joint. Figure 6 is a side view of a clip 150 according to a second embodiment of the present invention. The clip 150 is structurally and functionally similar to the clip 50 of the first embodiment, except in that the clip 150 of the second embodiment comprises a positioning ridge 160 extending along its sidewall for aiding the positioning of the clip 150 during installation. In some other embodiments, the positioning ridge may take another form of protrusion, such as one or more raised dots. During installation, an installer may adjust the vertical position of the clip 150 until the positioning ridge 160 abuts a top surface of the purlin 2 before fixedly attaching the clip 150 thereto. As such the anchor of the clip 150 extends precisely at a predetermined height above the purlin 2, thereby ensuring the elevation of the roofing sheet is consistent over each of the purlins 2 it is supported on. Figure 7 is a side view of a clip according to a third embodiment of the present invention. The clip 250 is structurally and functionally similar to the clip 50 of the first embodiment, except in that the clip 250 of the third embodiment is configured to fixedly attached to a leading perlin 2b, e.g. one that is adjacent to the drip-edge or eaves of a building, and comprises a gutter bracket 270 for supporting a gutter section 272 beneath the drip-edge of the roofing sheet 220. To aid rainwater drainage, the roofing sheet 20 is inclined to the horizontal plane. Specifically, the gutter bracket 270 extends from a sidewall of the clip 250 and perpendicular to the purlin 2b. The gutter bracket 270 is curved along its length and complements the curvature of the gutter section 272 supported thereon. The gutter section 272 may be a gutter extending along the entire length of the drip-edge or eaves of the building, or it may be a discrete section for forming the said gutter. In the illustrated embodiment, the gutter bracket 270 is integrally formed with the clip 250. In some other embodiments, the clip may comprise a tapped hole at its sidewall to which the gutter section may attach. In some other embodiments, the clip may be integrally formed with the gutter section. Advantageously, such an arrangement allows the roofing sheet 220 and the gutter section 272 to be attached to the purlin 2b by the same clip 250, thereby significantly reducing the work involved in the installation. Figure 8 is a truncated front view of a roofing assembly 310 according to a fourth embodiment of the present invention. The roofing assembly 310 is structurally and functionally similar to the roofing assembly 10 of the first embodiment, except in that the clip 350 is fixedly attached towards an end of a perlin 2, e.g. towards the eaves of the building, and a perimeter roofing sheet 320e comprises an edging portion 340 that fully covers the edge of the purlin 2, along the length of the sheet. The perimeter roofing sheet 320e comprises only a single first channel 322 configured to cover a second channel 324 of a leading roofing sheet 320b, thus together the leading roofing sheet 320b and the perimeter roofing sheet 320e are attached to the purlin 2 by a clip 350. As shown in Figure 8, the floor 321 of the perimeter roofing sheet 320e bends around the edge of the purlin 2 and extends downwardly to form the edging portion 340. The said edging portion 340 at least fully covers the side of the purlin 2. The edging portion 340 may be pre-fabricated with a predetermined separation between its first channel 322 and the edging portion 340, or it may be formed by heat bending the floor 321 of the perimeter roofing sheet 320e after it has already been attached to the clip 350, as such tailoring the separation between the first channel 322 and the edging portion 340 for each particular application. Figure 9 is a truncated perspective view of a pair of adjoining roofing sheets 420a, 420b according to a fifth embodiment of the present invention. The roofing sheets 420a, 420b are structurally and functionally similar to the roofing sheet 420 of the first embodiment shown in Figure 3, except in that the roofing sheets 420a, 420b are partially double-glazed roofing sheets for an improved thermal insulation, and that a leading lowered curved section of the sidewall at their first channels 422 are truncated to allow for an increased floor thickness of a proceeding roofing sheet. More specifically, the floors 421 of each of the roofing sheets 420a, 420b comprises an upper layer 421a and a lower layer 421b, with a gap sandwiched therebetween. The gap extends between, and parallel to, the channels 422, 424. The gap is sealed around its perimeter to limit air convection therein, as well as eliminating any rainwater leakage. 5 As shown in Figure 9, the first channel 422 of the roofing sheet 420a overlaps the second channel 424 of a preceding roofing sheet 420b. The sidewalls and the top sections of the channels 422, 424 comprise only a single layer of material and therefore the channels 422, 424 are not double-glazed. Taking into account an increased floor thickness of a preceeding roofing 10 sheet, a leading lowered curved section of the sidewall at each of the first channels 422 is truncated. The illustrated embodiment shows partially double-glazed roofing sheets 420a, 420b. In some other embodiments, the roofing sheet may be triple-glazed compising an intermeditate layer 15 between an upper layer and a lower layer, with a gap sandwiched between each of the layers. 18 11 24

Claims

1. A clip for attaching a roofing sheet onto an underlying support structure, comprising: a base fixedly attachable to a sidewall of the support structure such that, upon attaching the clip to the support structure, a first end of the base aligns with the support structure in a horizontal plane; andan anchor formed at a second end of the base, the anchor having side protrusions engageable with sidewalls in a channel of the roofing sheet for forming attachment therewith, wherein the anchor is arranged to rotate 90° about a vertical axis inside the channel of the roofing sheets to switch between a first orientation and a second orientation, wherein in the first orientation the side protrusions are separated from the channel, and in the second orientation the side protrusions engage opposite sidewalls of the channel to form the attachment.

2. The clip of claim 1, wherein upon attaching the clip to the support structure, the side protrusions sit proud of the support structure and extend in a direction parallel to the support structure.

3. The clip of claim 1 or claim 2, wherein each side protrusion comprises a lobed end for engaging with the sidewalls in the channel of the roofing sheet.

4. The clip of claim 3, wherein the lobed end has a greater thickness than other parts of the side protrusion.

5. The clip of claim 3 or claim 4, the lobed end has a substantially constant radius of curvature complementing at least a part of the cross-sectional profile of the sidewalls in the channel of the roofing sheet.

6. The clip of any one of the claims 1 to 5, wherein the anchor is insertable only in the first orientation through a slot opening that is formed by the sidewalls of the channel.

7. The clip of any one of the claims 1 to 6, wherein clip comprises a support for supporting a gutter section, and wherein upon attaching the clip to the support structure, the gutter section outwardly extends from the support structure and beneath an edge of the roofing sheet.

8. The clip of any one of the claims 1 to 7, wherein the first end of the base comprises an orifice through which a fixture extends to fixedly attach the clip to the sidewall of the support structure.

9. The clip of any one of the claims 1 to 8, wherein the base of the clip comprises a positioning ridge extending along its sidewall, wherein upon attaching the clip to the support structure the positioning ridge rests on a top surface of the support structure for aligning the clip with the support structure.

10. A roofing assembly, comprising the clip of any one of the preceding claims and a roofing sheet, wherein the roofing sheet is attached to the underlying support structure by the clip that is fixedly attached to a sidewall of the support structure.

11. The roofing assembly of claim 10, comprises a plurality of adjoining roofing sheets, wherein at least one channel of one of the roofing sheets overlaps another channel from an adjoining roofing sheet, wherein both the said channel and the adjoining channel are attached together to the support structure by the clip.

12. A method of attaching a roofing sheet to an underlying support structure by the clip of any one of the preceding claims, comprising the step of:inserting the anchor of the clip into the channel of the roofing sheet to form the attachment.

13. The method of claim 12, further comprises the step of:positioning the roofing sheet at a predetermined location on top of the support structure prior to the inserting;rotating the clip about the vertical axis after the inserting, as such the side protrusions of the anchor engages with the channel to form the attachment; andfixedly attaching the first end of the clip to the sidewall of the support structure.

14. The method of claim 13, further comprises the step of:biasing the clip towards the sidewall of the support structure after the rotating, so as to cause the clip to slide along the channel to abut the sidewall prior to forming the attachment.18 11 24

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