METHOD FOR COVERING A FLAT ROOF

Abstract

 The invention relates to a method for covering a flat roof with a number of adjacent strips of roof covering material, the method comprising the steps of;
- clamping a section of a strip of roof covering material between clamping members by exerting and maintaining a clamping force by the clamping members to the section,
- mounting the clamping members to a roof substructure that is configured to exert a holding force to the clamping members,
wherein the method comprises setting the clamping force and the holding force independently.

Description

FIELD OF THE INVENTION

[0001] The invention relates to a method for covering a flat roof with a number of adjacent strips of roof covering material.

BACKGROUND OF THE INVENTION

[0002] Buildings have roofs. Roofs must be able to withstand all weather conditions for decades. The weather conditions include effect by the sun, frost, precipitation, wind, storms, etc. The roof must not only be permanently waterproof, but it must also be proven storm-resistant according to the applicable standards.

[0003] Industrial buildings mainly have large flat roofs. An industrial flat roof is made up of different parts, firstly a mostly steel skeleton, secondly a substructure and lastly a roof covering construction. The substructure is usually a corrugated metal sheet, also referred to as "deep deck profiles". The roof covering construction consists of a vapor barrier, insulating material in sheet form and a single layer mechanically fastened roofing system made of plastic roofing material.

[0004] In order to be sufficiently storm-proof, the roofing system must be carefully attached to the substructure. In mechanical fastening of single-ply roofing systems, the usual method is to fasten one side or 'edge' of the roofing membrane to the substructure with mechanical fasteners. As mechanical fasteners, screws with metal pressure distribution plates as well as screws with a plastic sleeve are used. The plastic sleeve is also referred to as "tube washer". The metal pressure distribution plates can also be referred to as "washers". The adjacent roofing membrane is arranged to overlap over the edge as to cover the fasteners and is then welded to the roofing membrane. The fastening in the overlap is very efficient.

[0005] In accordance with current applicable standards, the required wind resistance is calculated. Based on the calculation, the number of fasteners that must be applied is determined. Generally, in the corner and edge zones, considerably more fasteners are needed per square meter as compared to central sections of the roof surface. A number of aspects do influence the wind load capacity of a roofing covering. The aspects include for instance; an even distribution of fasteners along the edge, maintaining a correct edge zone from a fastener, the strength of the roofing membrane, the pull-out value of the fasteners and the strength of a metal profile if present. All of these aspects can be coordinated to obtain the required wind load capacity. In practice, it is important that the fasteners are evenly spaced from each other, in accordance with the product installation instructions of the manufacturer of the roofing system.

[0006] In connection with wind load capacity, the resistance to tearing of the roofing covering material is a general point of concern. Reinforcing the roofing material is a solution as chosen in US8590260BB. Another solution is to apply a screw with a follower plate, also "washer", that distributes the force over a larger surface of the roofing membrane. Instead of a follower plate, an elongate mounting profile is also used, like for example in DE202005006231U and EP1348821A2, wherein the mutual distances of the fasteners are also determined by the mounting profile. Not only the distribution but also the extent to which the roofing membrane is pressed against or towards the insulation material is decisive. The roof covering construction includes insulation material that is only limited pressure-resistant and also will relax over time. This means that the extent to which the roofing membrane is pressed against or towards the insulation material will reduce in time. A known solution in EP1348821A2 is to fix the distribution plate to the roofing membrane by heating with induction.

[0007] EP262694 is not about attaching a roof covering material as top layer to the roof covering construction. Instead, EP262694 suggest another solution wherein mutually overlapping parts of the roof covering strips are stretched by means of a bar that is clamped in a U-profile. The U-profile is fixed to the surface of the roof.

[0008] It would be desirable to provide an improved method for covering a flat roof with a number of adjacent strips of roof covering material, wherein the method alleviates some or all of the above problems.

SUMMARY OF THE INVENTION

[0009] In one aspect, the present application provides a method for covering a flat roof with a number of adjacent strips of roof covering material, the method comprising the steps of;

• clamping a section of a strip of roof covering material between clamping members by exerting and maintaining a clamping force by the clamping members to the section,
• mounting the clamping members to a roof substructure that is configured to exert a holding force to the clamping members,

[0010] wherein the method comprises setting the clamping force and the holding force independently.

[0011] The ability to set the clamping force and the holding force independently, importantly improves the manageability of the wind load capacity of the roof covering.

[0012] "Covering" the roof is to say that a covering is applied to the flat roof, wherein the covering protects the building from effect of rain and wind. Roof covering material is also referred to as "roofing membrane" and "roofing felt". Important is that the roof covering material is applied in the form of long strips. The long strips are seamed together at their long edges. The welding or seaming is done on site, that is on the roof of the building construction.

[0013] "Independently" means that both the clamping force and the holding force can be adjusted individually according to wishes, needs and prescriptions.

[0014] According to an embodiment, the section comprises an edge portion of the strip of roof covering material. The section comprising an edge portion of the strip of roof covering material facilitates clamping of the section between the clamping members.

[0015] According to an embodiment the section comprises a number of spaced edge portions. The section comprising a number of spaced edge portions allows to manage the wind load capacity of the roof covering along the entire length of the strip of roof covering material. The spaced edge portion do preferably have a similar or identical spacing between adjacent edge portions. This improves load distribution to the roof covering material. However, it will be clear that any suitable spacing of edge portions is conceivable.

[0016] According to an embodiment, the method comprises clamping a respective edge portion of the number of spaced edge portions between respective clamping members. This all the more facilitates clamping of the roof covering material. It will be clear that all of the numbers of edge portions can be clamped. Clamping members can be operated in unity or separately depending on the configuration of the clamping members. Clamping members can take the form of individual pairs of opposite clamping members. An elongate profile of several meters is also conceivable.

[0017] According to an embodiment, the method comprises;

• overlapping an edge of the strip roofing material as well as the clamping members with a neighbouring strip of roof covering material,
• forming a waterproof seam at an overlap between the strip and neighbouring strip.

[0018] This overlapping and forming of a seam all the more points out that a covering is applied to the flat roof, wherein the covering protects the building from effect of rain and wind.

[0019] The present application also provides a system for attaching a number of adjacent strips of roof covering material to a substructure of a flat roof, the system comprising;

• a clamping system comprising opposite plate members for clamping a section of roof covering material there between, and
• a mounting system for securing the clamping system to the substructure with a holding force,

wherein the clamping system is configured to set a clamping force independently from the holding force. The system provides the ability to set the clamping force and the holding force independently, and importantly improves the manageability of the wind load capacity of the roof covering. The opposite plate members distribute a clamping force to avoid damage to the roof covering material.

[0020] According to an embodiment the system comprises an operating member for applying the clamping force to the clamping system. The operating member facilitates clamping of the section of roof covering material and manageability thereof. The operating member can involve a wedging action by a bevelled edge, a screw action through a thread. It will be clear that any suitable member is conceivable.

[0021] According to an embodiment of the system, the operating member comprises a screw thread, in particular at least a half turn of screw thread. The operating member comprising a screw thread, facilitates application of the clamping force by a turning motion. This also enable to integrate the operating member with a threaded fastener or application of a threaded fastener.

[0022] According to an embodiment of the system, the mounting system comprises a fastening member for securing the clamping system to the substructure. Preferably, the fastening member is provided with the operating member, meaning that the operating member is arranged on the fastening member. This all the more facilitates application of the clamping force by a turning motion.

[0023] According to an embodiment, the system comprises a locking system for maintaining the clamping force to the clamping system. The locking system maintaining the clamping force to the clamping system guarantees a wind load capacity during the entire product life of the roof covering system. The locking system may involve a snap fit action, a deformable hinge, opposite flanges, etc. Any suitable locking system is conceivable.

[0024] According to an embodiment of the system, the fastening member is provided with the locking system. The fastening member being provided with the locking system reduces the number of parts and facilitates installing of the roof covering system.

[0025] According to an embodiment of the system, the locking system comprises a distal flange. The distal flange provides a stop surface for the locking system that is visible for an operator who is installing the roof covering system.

[0026] According to an embodiment of the system, the fastening member comprises a screw and a sleeve. Preferably, the operating member and the locking system are provided with the sleeve. The division of the fastener in a screw and a sleeve provides freedom in choice of material which in turn facilitates to avoid thermal bridges to the substructure. A combination of a metal screw and a plastic sleeve is conceivable. The sleeve extends through isolation material and the screw then secures the sleeve and the roof covering material to the substructure.

[0027] According to an embodiment of the system, the sleeve comprises an external screw thread at a proximal tip of the sleeve. The external screw thread facilitates installation of the sleeve through the isolation material. It is conceivable that only a limited number of turns of screw thread is applied to the sleeve. Any number of turns suffices as long as penetration power of the sleeve is improved.

[0028] According to an embodiment of the system, the clamping system comprises a number of opposite plate members and a spacing member positioning the opposite plate members along a strip of roof covering material. The spacing member enables a predetermined spacing of the opposite spacing members with respect to adjacent and other pairs of opposite spacing members. In turn this all the more improves the manageability of the wind load capacity of the roof covering.

[0029] According to an embodiment of the system, the spacing member comprises a flexible element, like a wire. The spacing member comprising a flexible element enables to roll up the spacing member into a bobbin. Such a rolled up spacing member may also contain plate members.

[0030] According to an embodiment of the system, the clamping system comprises a hinge system coupled with the opposite plate members for allowing to move the plate members between an open position to receive the section between the plate members, and a closed position to clamp the section. The hinge system facilitates clamping of the section of roof covering material in a controlled manner. Any hinge system is conceivable, like a living hinge, as long as the plate members can rotate between the open position and closed position. A living hinge is a hinge system that depends on deformation of material and has no parts that slide with respect to each other. Such a living hinge can also contribute, or be part of, or constitute the locking system.

[0031] According to an embodiment of the system, the opposite plate members comprise a hole to receive a fastening member. The opposite plate members comprising a hole enables to build a compact system wherein still a clamping force is distributed over the roof covering material. The hole can be a central hole. However, an off-centre hole is conceivable as well as this may safe roof covering material since an overlap may be smaller.

[0032] According to an embodiment of the system, the hinge system defines a pivot axis that in use coincides with an edge of the strip of roof covering material. The hinge system defining a pivot axis that in use coincides with an edge of the strip of roof covering material enables to optimize the amount of roof covering material around the central hole and therefore prevent tearing of the roof covering material.

[0033] According to an embodiment of the system, the central hole and the operating member is configured such that the screw thread of the operating member can be turned through the central hole. This enables to apply a clamping force and locking the clamping members between the distal flange of the locking system and the screw thread of the operating member. In other words, the screw thread of the operating member has a function in, or is part of, both the operating member and the locking system. The distal flange and the screw thread delimit a predetermined gap. This is very beneficial since this gap defines a clamping force exerted on the roof covering material. This clamping force is therefore independent from an operator as well as independent from the substructure.

[0034] According to an embodiment of the system, the opposite plate members comprise cooperating projections and cavities to fold the section of roof covering material when the plate members are in closed position. The projections and cavities to fold the section of roof covering material facilitates clamping of the section of roof covering material between the opposite plate members.

[0035] According to an embodiment of the system, the clamping system and mounting system are connected such that the clamping system can rotate with respect to the mounting system to follow movement of the roof covering material in case of bulging due to wind load. The ability of the clamping system to rotate improves the wind load capacity all the more. When a strip of roof covering material bulges, the clamping system can align with the roof covering material. This reduces stress in the roof covering material. Also, the pull-out capacity of the mounting system is improved.

[0036] The present application also provides a sleeve configured and suitable for use in a system as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The invention will be described further with respect to embodiments shown in the drawings.

Fig. 1 shows a perspective view of a prior art flat roof construction;

fig. 2 shows a detail of fig. 1;

fig. 3 shows the clamping system of an embodiment of the system according to the invention,

fig. 4 is a cross-sectional side view of the clamping system of fig. 3 and a fastener;

fig. 5 is a top view of a clamping system of fig. 3;

fig. 6 shows the clamping system of another embodiment of the system according to the invention;

fig. 7. is a cross sectional side view of the fig. 6;

fig. 8 is a cross sectional side view of a system according to the invention using the clamping system of fig. 6;

fig. 9 shows the clamping system of an even further embodiment of the system according to the invention;

fig. 10. Is a cross sectional side view of the fig. 9;

fig. 11 is a top view of an even further embodiment of the system according to the invention; and

fig. 12 is a side view of the embodiment of fig. 11.

DESCRIPTION

[0038] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the figures. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0039] Fig. 1 shows a perspective view of a prior art flat roof construction 1. Such a flat roof construction 1 is very common for e.g., industrial buildings. The flat roof construction 1 is made up of different subsystems. Firstly, the flat roof construction 1 comprises a steel frame 2 that is partly shown and is also referred to as "skeleton". Secondly the flat roof construction 1 comprises a substructure 3 that usually takes the form of a corrugated metal sheet 4. Lastly the flat roof construction 1 comprises a a roof covering system 5. The roof covering system 5 comprises a vapor barrier layer 6, an insulating material 7 usually in sheet form, as well as a single layer of roof covering material 8.

[0040] The roof covering material 8 is mechanically fastened to the substructure 3 to provide wind load capacity. The roof covering material 8 can be made of plastic synthetic roofing material, however it will be clear that any suitable roof covering material will suffice. The layer of roof covering material 8 is usually in the form of strips 9 of roof covering material. Adjacent strips 9 of roof covering material do overlap at an overlap section 10 and are attached together to form a watertight layer of roof covering material 8. At the overlap section 10, the strips 9 are welded together to form a watertight seam. The strips 9 of roof covering material extend in length perpendicular to a length orientation of the corrugated metal sheet 4 to ensure that fasteners (not shown here) contact a number of adjacent corrugated metal sheets 4.

[0041] Fig. 2 shows a detail of fig. 1. The layer of roof covering material 8 is usually in the form of strips 9 of roof covering material. Two adjacent strips 9 of roof covering material do overlap at an overlap section 10. The edges 12 of the two adjacent strips 9 of roof covering material that overlap are attached together to form a watertight layer of roof covering material 8. The edges 12 are heat bonded or welded in this case. However, any suitable way of attaching the edges 12 to each other is conceivable.

[0042] At the overlap section 10, mechanical fasteners (not shown) will be arranged at the opening 11 to provide a roofing system with one layer of roofing material 8 that is attached to the substructure 3. The metal profiled sheet of the substructure 3 is not visible for an operator at the time of installation of the roofing material and this is a problem for an operator. If an opening 11 and corresponding fastener is too close to the edge of roofing material, the roofing material may easily tear. When, on the other hand, the mechanical fasteners are placed too far from the edge, the overlap between strips 9 is too big and results in a loss of material.

[0043] Fig. 3 shows the clamping system 13 of an embodiment of the system according to the invention. The clamping system 13 comprises opposite plate members 14a, 14b, also referred to as clamping members. The plate members 14a, 14b have a similar clamping surface in this case. In use, the clamping surface contacts the roof covering material 8. The opposite plate members 14a, 14b distribute a clamping force such that deformation of the roof covering material 8 is controlled as much as possible. In other words, the opposite plate members 14a, 14b distribute a clamping force in such a way that roof covering material is slightly deformed and not able to slip through the plate members. The opposite plate members 14a, 14b clamp a section 15 of roof covering material 8 between the plate members 14a, 14b. The clamping system 13 is configured to set a clamping force independently from any holding force to the substructure (not shown here).

[0044] The clamping system 13 comprises a hinge system 19. The hinge system 19 is coupled with the opposite plate members 14a, 14b for allowing to move the plate members with respect to each other. The hinge system 19 allows the opposite plate members 14a, 14b to rotate between an open position (not shown here) and a closed position as shown here. In the open position, the opposite plate members 14a, 14b form a receiving area to accommodate the section 15 of roof covering material 8 between the plate members 14a, 14b. In the closed position, the opposite plate members 14a, 14b do clamp the section 15 in between the opposite plate members 14a, 14b. In this case, the hinge system 19 is a living hinge system meaning that the pivoting motion depends on deformation of material. As a result, the hinge system 19 and the opposite plate members 14a, 14b are integrally formed. Here, the hinge system 19 and the opposite plate members 14a, 14b are of one piece and made of metal.

[0045] The hinge system 19 defines a pivot axis 20 around which the opposite plate members 14a, 14b can rotate. In use, the pivot axis 20 coincides with an edge 21 of the strip 9 of roof covering material 8.

[0046] The clamping system 13 comprises a number of opposite plate members 14a, 14b and a spacing member 17. The spacing member 17 assists in positioning the opposite plate members 14a, 14b along the strip 9 of roof covering material 8. Here, the spacing member 17 comprises a flexible element 18 like a wire 23 that can be wind-up to form a bobbin.

[0047] The opposite plate members 14a, 14b comprise a central hole 22 to receive a fastening member (not shown here).

[0048] Fig. 4 shows in general terms a system 1 for attaching a number of adjacent strips 9 of roof covering material to a substructure 3 of a flat roof. More specific, fig. 4 is a cross-sectional side view of the clamping system 13 of fig. 3 and a fastener 25. The system 1 comprises a mounting system 24 for securing the clamping system 13 to the substructure 3 with a holding force. The holding force is determined by the fastener 25 and the substructure 3. The clamping force is determined by the clamping system 13. In other words, the system 1 is configured to set a clamping force independently from the holding force.

[0049] As shown, the section 15 comprises an edge portion 26 of the strip 9 of roof covering material. The clamping system 13 clamps the section 15 including the edge portion 26.

[0050] The system 1 comprises an operating member 27 for applying the clamping force to the clamping system 13. In this case, the operating member 27 comprises a screw thread 28. The screw tread 28 runs between half and a whole turn around a central axis 30 of the distal fastener 25. In use, the screw thread 28 pulls the clamping system tight against the distal flange 29. The mounting system 24 comprises a proximal fastening member 31 for securing the clamping system 13 to the substructure 3. In this case, the distal fastening member 25 is provided with the operating member 27. Here, the distal fastening member 25 comprises a sleeve 32 with a hollow 33. The proximal fastening member 31, usually a metal screw, is passed through the hollow 33 to engage with the substructure 3.

[0051] The system 1 comprises a locking system 34 for maintaining the clamping force to the clamping system 13. Her, the distal fastening member 25 is provided with the locking system 34. The locking system 34 comprises the distal flange 29 and an opposite flange 35. The clamping system 13 is maintained between the distal flange 29 and the opposite flange 35. The screw thread 28 gradually transitions into the opposite flange 35. In addition, the screw thread 28 is self braking and therefore also maintains the clamping system 13 in between the distal flange 29 and the opposite flange 35 during the product life cycle of the system 1.

[0052] The fastening member 25 comprises a screw 31 and a sleeve 32. The screw 31 secures the system 1 to the substructure 3. In this case, the operating member 27 and the locking system 34 are provided with the sleeve 32. The sleeve is made of an engineered plastic and is manufactured by injection moulding. The sleeve 32 extends through the isolation material 7. The sleeve 32 comprises an external screw thread 38. The external screw thread 38 is also referred to as "shredder thread". The external screw thread 38 facilitates easy penetration of the sleeve 32 through the isolation material 7. The external screw thread 38 is provided at a proximal tip of the sleeve 32.

[0053] The opposite plate members 14a, 14b comprise a central hole 22 to receive the fastening member 24, also referred to as "mounting system". The central hole 22 and the operating member 27 is configured such that at least the screw thread 28 of the operating member 27 can be turned through the central hole 22.

[0054] The opposite plate members 14a, 14b comprise cooperating projections 37 and cavities 36. The cooperating projections 37 and cavities 36 do fold the section 15 of roof covering material when the plate members 14a, 14b are in closed position.

[0055] During use, the following steps are executed in the method for covering a flat roof with a number of adjacent strips 9 of roof covering material 8. Firstly, a section 15 of a strip 9 of roof covering material is clamped between clamping members 14a, 14b. Therefore, a clamping force is exerted and maintained to the clamping members of the clamping system. The operating member 27 exerts the clamping force. In this case, a turning motion of the sleeve 32 is transformed into a translation of the clamping members 14a, 14b towards each other by the screw thread 28.

[0056] As another step, the clamping members of the clamping system 13 are mounted to a substructure 3. Therefore, a mounting system 24 is provided that is configured to exert a holding force to the clamping members 14a, 14b. The steps of clamping and mounting can be executed subsequently. It is however conceivable to execute the steps of clamping and mounting in part simultaneously.

[0057] The presence of both the clamping system 13 and the mounting system 24 enables the step of setting the clamping force and the holding force independently.

[0058] Fig. 5 is a top view of a clamping system 13 of fig. 3. The clamping system 13 comprises a number of opposite plate members 14a, 14b. The clamping system 13 comprises a hole 22 to receive a fastening member 24 (partly shown). Here, the hole 22 is a central hole 22. The central hole 22 is provided in the opposite plate members 14a, 14b to receive the fastening member 24.

[0059] The fastening member 24 comprises an operating member 27 for applying the clamping force to the clamping system 13. The operating member 27 comprises a distal flange 19. In use, the distal flange 19 abuts an upper plate member 14a of the two opposite plate members 14a, 14b. The operating member 27 comprises a screw thread 28. The screw tread 28 runs between half and a whole turn around a central axis 30 of the distal fastener 25. The screw tread 28 can be turned through the hole 22. Thereafter, the screw thread 28 pulls the clamping system 13 tight against the distal flange 29. Thus, the clamping system 13 is locked between the distal flange 29 and the screw thread 28. In other words, the clamping system 13 is maintained between the distal flange 29 and the screw thread 28. In this case, the screw thread 28 gradually transitions into the opposite flange 35. This results in locking of the clamping system 13 between the distal flange 29 and the opposite flange 35.

[0060] Fig. 6 shows the clamping system 13 of another embodiment of the system 1 according to the invention. The clamping system 13 is described under reference to figures 6-8. The clamping system 13 comprises opposite plate members 14a, 14b. In open position as shown in fig. 7, the opposite plate members 14a, 14b make about an L-shape in cross sectional view. In this case, the clamping system 13 takes up the form of an elongate profile 13. The elongate profile 13 comprises a number of holes 22, each hole 22 to receive a fastening member (not shown). Here, the holes 22 are mutually spaced at a spacing distance s. The improves manageability of the wind load capacity of the roof covering system.

[0061] The layer of roof covering material 8 is in the form of strips 9 of roof covering material. Adjacent strips 9 of roof covering material do overlap at an overlap section 10 and are attached together to form a watertight layer of roof covering material 8. As shown the clamping system 13 clamps an edge portion 26 of one strip 9 of roof covering material 8. The clamping system 13 is attached to the substructure (not shown) through the insulation material 7. Therefore, fasteners (not shown) are applied to the holes 22. The holes are referred to with 22a, 22b in case the clamping system is in open position. The adjacent strip 9 of roof covering material 8 covers the strip 9 and clamping system 13 at the overlap section 10 to form a watertight roof covering once the strips 9 are mutual adhered.

[0062] Fig. 9 shows the clamping system 13 of an even further embodiment of the system 1 according to the invention. The clamping system 13 is described under reference to figures 9-10. The clamping system 13 comprises opposite plate members 14a, 14b. In open position as shown in fig. 10, the opposite plate members 14a, 14b make about an L-shape in cross sectional view. In this case, the clamping system 13 takes up the form of an elongate profile 13. This even further embodiment differs with the once shown in fig. 6-8 in that the shape of the opposite plate members 14a, 14b is different. The upper plate member 14a has individually shaped portions 39 compared to the lower upper plate member 14b that is still an elongate profile. It is conceivable that it is possible to move the individual portions 39 from the open tot the closed position. The elongate profile 13 comprises a number of holes 22, each hole 22 to receive a fastening member (not shown). Here, the holes 22 are mutually spaced at a spacing distance s. The improves manageability of the wind load capacity of the roof covering system. The holes are referred to with 22a, 22b in case the clamping system 13 is in open position.

[0063] Fig. 11 is a top view of an even further embodiment of the system according to the invention. Fig. 12 is a side view of the embodiment of fig. 11. The system differs with the one shown in fig. 4 in that the clamping system 13 and mounting system are connected such that the clamping system 13 can rotate with respect to the mounting system. The clamping system 13 is still locked between the distal flange 29a and the screw thread 28a however the part of the thread that ends as a lower flange has a rounded section that bends away from the distal flange 29a. The distal flange 29a is asymmetric and constrains rotation of the clamping system 13 in one direction but allows rotation of the clamping system 13 in a direction opposite to the one direction. The clamping system 13 can thus rotate around an imaginary axis of rotation 41 towards a position indicated by the dashed line. The rotation of the clamping system 13 to follow movement of the roof covering material 9 in case of bulging due to wind load. The clamping force is maintained by a locking system in the form of snapping harpoons 40. The hole 22 is off-centre in this case, and is off-centre in view of the clamping system 13, over a distance d. This all the more allows the clamping system 13 to follow movement of the roof covering material 9 in case of bulging due to wind load.

[0064] While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention is not limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. Method for covering a flat roof (1) with a number of adjacent strips (9) of roof covering material, the method comprising the steps of;

- clamping a section of a strip of roof covering material between clamping members (14a, 14b) by exerting and maintaining a clamping force by the clamping members to the section,

- mounting the clamping members to a roof substructure (3) that is configured to exert a holding force to the clamping members,

wherein the method comprises setting the clamping force and the holding force independently.

2. Method according to claim 1, wherein the section comprises an edge portion of the strip of roof covering material.

3. Method according to claim 1 or 2, wherein the section comprises a number of spaced edge portions, and wherein the method prefereably comprises clamping a respective edge portion of the number of spaced edge portions between respective clamping members.

4. System for attaching a number of adjacent strips (9) of roof covering material to a substructure (3) of a flat roof, the system comprising;

- a clamping system (13) comprising opposite plate members for clamping a section of roof covering material there between, and

- a mounting system (24) for securing the clamping system to the substructure with a holding force,

wherein the clamping system is configured to set a clamping force independently from the holding force.

5. System according to claim 4, comprising an operating member for applying the clamping force to the clamping system.

6. System according to claim 5, wherein the operating member comprises a screw thread, in particular at least a half turn of screw thread.

7. System according to any preceding claim 4 - 6, wherein the mounting system comprises a fastening member for securing the clamping system to the substructure, and wherein preferably the fastening member is provided with the operating member.

8. System according to any preceding claim 4 - 7, comprising a locking system for maintaining the clamping force to the clamping system, wherein prefereably the fastening member is provided with the locking system.

9. System according to any preceding claim 7-8, wherein the fastening member comprises a screw and a sleeve, wherein the operating member and the locking system are preferably provided with the sleeve.

10. System according to claim 9, wherein the sleeve comprises an external screw thread at a proximal tip of the sleeve.

11. System according to any preceding claim 4 - 10, and wherein the clamping system comprises a number of opposite plate members and a spacing member positioning the opposite plate members along a strip of roof covering material.

12. System according to any preceding claim 4 - 11, wherein the clamping system comprises a hinge system coupled with the opposite plate members for allowing to move the plate members between an open position to receive the section between the plate members, and a closed position to clamp the section.

13. System according to any preceding claim 4 - 12, wherein the opposite plate members comprise a hole to receive a fastening member, and wherein prefereably the hole and the operating member is configured such that the screw thread of the operating member can be turned through the hole.

14. System according to any preceding claim 4 - 13, wherein the clamping system and mounting system are connected such that the clamping system can rotate with respect to the mounting system to follow movement of the roof covering material in case of bulging due to wind load.

15. Sleeve configured and suitable for use in a system according to any of preceding claims 9-14 and comprising any sleeve features as defined in any of preceding claims 9 - 14.

Drawing