WO1996031670A1

WO1996031670A1 - A method for fastening a sealing foil to an underlying structure, a bonding element and a non-penetrating fastening system in accordance with said method

Info

Publication number: WO1996031670A1
Application number: PCT/NL1996/000143
Authority: WO
Inventors: Gijsbert Van Malde
Original assignee: Van Beek Beheer B.V.
Priority date: 1995-04-04
Filing date: 1996-04-04
Publication date: 1996-10-10
Also published as: EP0819202A1; NL1000032C2; DE69606287D1; DE69606287T2; AU5126096A; ATE189025T1; EP0819202B1

Abstract

A method for fastening a sealing foil (4) to an underlying structure (1). Before the sealing foil is provided, bonding elements (2) are provided on or in the underlying structure. In many cases gravel or the like is provided on the sealing foil with a view to weighting said sealing foil. The use of a thermal adhesive element as the fixing means and a proper heat-conducting foil as the sealing foil makes it possible to make the joint between bonding element and sealing foil after the sealing foil has been provided.

Description

Title: A method for fastening a sealing foil to an underlying structure, a bonding element and a non- penetrating fastening system in accordance with said method.

Description

The invention relates to a method for fastening a sealing foil to an underlying structure, comprising the steps of providing bonding elements on or in said underlying structure and subsequently providing said sealing foil.

The invention furthermore relates to a non-penetrating fastening system comprising a sealing foil and bonding elements obtained in accordance with said method.

The invention furthermore relates to a bonding element for use in conjunction with said method or with said non- penetrating fastening system.

The general technical field to which the invention applies is the field of non-penetrating fastening systems for sealing foils. In particular those systems wherein the foil functions to seal architectural structures and specifically those systems wherein said foil is an EPDM (Ethene, Propene, Diene, Monomer) membrane and wherein said structure is a roof.

Many existing flat and slightly sloping roofs are still sealed with multilayer, bituminous roofing materials provided in the form of strips. The roofing of more modern systems often consists of a single-layer synthetic foil, usually an elastomeric EPDM foil. This foil may be provided on a roof, inter alia in the form of strips, whereby the seams between the strips are sealed on site. It is preferred, however, to use the EPDM foil in the form of a prefabricated membrane, which can be handled more efficiently. In that case the seams between the strips are mechanically vulcanized under ideal conditions at the factory. Membranes of more than 2500 m² having the exact shape and dimensions of the structure to be sealed are not exceptional. Foil membranes of this type must somehow be fixed with respect to the base to be sealed or to the roof construction, inter alia in order to be able to withstand wind loads. Said fixing of the foil may for example take place by weighting it with a layer of gravel or the like, glueing it to the base or fastening it to the underlying structure by mechanical means.

A weighted foil system is a simple and reliable system. It has the drawback of being heavy, however. As a result of this such a system requires a stronger and thus costlier roof construction than other systems. In addition to that the slope of a gravel-weighted roof must not exceed 10% if no special provisions are made, this in connection with the risk of the weighting layer sliding off.

The cost price of glued foil systems is relatively high, in connection with the amount of glue which is required and the laborious operations. The roof construction, which often consists of light-weight profiled metal sheets, makes it necessary to first fasten a flat layer (usually a thermal insulating material) thereto first by means of fasteners, with the sealing foil subsequently being glued onto said layer. When the roofing is to be removed it is thus practically impossible to keep the materials used in the roof construction apart and remove them without damaging them, as a result of which the materials cannot be recycled or reused. The glues which are required are inflammable because of the solvents they contain. The glue vapours being released when processing the glue constitute an environmental and health hazard. The application of glues can only take place in certain weather conditions.

Mechanically fastened foil systems may be divided into two groups, namely: foil penetrating systems and non- penetrating systems. Each system has its own specific advantages and disadvantages. The drawback of mechanically fastened foil penetrating systems is that one or more components of the system are fastened to the base by means of a linear mechanical fastener (for example a screw or the like) through an opening in the membrane. This opening in the sealing foil must subsequently be expertly sealed, usually by hand, which is laborious and costly, as a result of which there is moreover greater risk of leakage than is the case with non-penetrating systems.

A number of non-penetrating mechanical fastening systems consist of clamping elements, which are built up of rigid and/or semi-flexible components. One of the components is thereby fastened to the base by one or more linear fasteners.

The sealing foil is then spread out over said elements, after which a second component is provided, which second component deforms the foil and clamps it down in a recess or on a protrusion of the first componenthaving a more or less mushroom-shaped section. In order to be able to do so either one of the two components must be slightly flexible. In most cases the latter flexible component is subsequently fixed by means of a third component.

The elements are mostly in the shape of a disc or a strip. A clamping element of this type has relatively large dimensions and is relatively costly from a point of view of the manufacturing technique, the materials and the method of processing that are used. Said deformation and clamping down lead to creases and/or tensions in the foil. Most clamping elements have a high profile, in some cases as high as a few cm, as a result of which accidents, for example personnel tripping over an element, will not be entirely imaginary. With some strip-shaped systems the discharge of water from the roof surface may moreover be disturbed as a result of this. With a number of internally clamping systems the membrane is moreover slightly "lifted" from its base. This leads to the formation of a so-called "dead volume" between the base and the underside of the membrane. In that case the advantageous feature of a foil membrane i.e., its capacity to adhere to a wind-tight base as adhering thereon like a suction cup, as it were, will be partially lost. In most cases these fastening systems are clearly and undesirably visible, among other things because of their dimensions and because of the presence of the component on the foil material. Another non-penetrating mechanical fastening system is the bonding element system. The bonding element may be in the form of a disc or a polygonal plate or an strip and will for example consist of a bonding plate or a bonding piece. The bonding plate consists of a rigid material and the bonding piece consists of a foil-like material, which is often the same material as the material used for the sealing foil, and is in some cases provided with reinforcing tissue. Both the bonding plate and the bonding piece are fastened to the base by means of linear fasteners, in the case of the bonding piece always in combination wit a washer. With these systems the underside of the sealing foil is glued or chemically or thermally welded to the bonding element. Usually a contact glue or a pressure-sensitive self-adhesive tape is used for said glueing. For said chemical welding a welding fluid is applied to the bonding element, which usually consists of or is coated with the same synthetic material as the material of the sealing foil. The sealing foil is directly provided over said bonding element, whereby the sealing foil must also be suitable for making such a chemical weld, of course, and is pressed down on said chemical welding fluid.

Two methods may be used to carry out said thermal welding: The first method is a hot air method. When this method is used a bonding element, which entirely consists of or which is coated with a suitable thermoplastic synthetic material at its upper side, is fastened to the base to be sealed by means of a linear fastener. Just before the sealing foil, which is likewise thermoplastic, is provided on said bonding element both the synthetic material on said bonding element and the underside of said sealing foil at the location of said bonding element are heated to welding temperature by means of hot air equipment. Then the surfaces of the two materials are quickly pressed together and the joint has been made.

With the second thermal welding method a metal plate coated with a suitable thermoplastic synthetic material is fastened to the base to be sealed by means of a linear fastener. The sealing foil is provided over said plate. Then a high-frequency magnetic field is generated in the metal plate, from the side of the sealing foil facing away from the base, by means of special equipment. As a result of this the metal plate will heat up and the underside of the (likewise thermoplastic) foil and the thermoplastic coating of the plate will heat up to welding temperature. At the same time the sealing foil is pressed down on the plate and the welding connecting has been made.

The advantage of the bonding piece method over the bonding plate method is that the joint is not subjected to peeling forces. Said peeling forces are generated on the glued or welded joint between a rigid bonding element and the sealing foil when the sealing foil bulges out between the fastening points as a result of a pressure difference between the upper side and the bottom side, which may be caused by the wind. When a bonding piece is used, the joint will bend along with the bulging sealing foil and will be subjected to shear forces. With that construction, whereby the bonding piece is provided with a mechanical by reinforcing material, the tearing strength of said bonding piece with respect to the linear fastener and the washer is moreover increased. In addition to that a reinforced bonding piece will reduce the so-called "back-peel" forces, to which a joint comprising a non-reinforced bonding piece may be subjected as a result of the elongation of said piece when being loaded mechanically. With the high-frequency welding system it is possible to finish or fix the (roof) sealing foil at the (roof) edges before making the joints at the bonding points, which constitutes a great advantage from a point of view of efficiency in processing of the foil. The drawback of this system, however, is that a metal plate of costly aluminium or yellow brass coated with a thermoplastic synthetic material must be used. In addition to that the system is only considered to be suitable for thermoplastic foils and requires the use of special high-frequency equipment. Furthermore the joint between the rigid plate and the foil is loaded for peel.

The patents referred to below disclose inventions and techniques with are used in non-penetrating bonding element fastening systems.

US Patent No. 4,161,854 discloses a non-penetrating fastening system, wherein a plurality of discs are fastened to a thermally insulating base, to which the sealing foil may be adhered by glueing or chemical or high-frequency welding. The fastening discs are fitted with a provision which prevents them from becoming prematurely detached from said underlying structure.

US Patent No. 4,437,283 discloses a penetrating fastening system for fastening a flexible roofing foil to a roof or a building, wherein a double-sided bonding tape provides a joint between the fastening element and the foil, and whereby a similar tape is used to seal the membrane- penetrating fastening system when using an EPDM foil. US Patent No. 4,688,316 discloses a bonding plate system wherein the bonding plate has been provided with a self-adhesive gum tape in advance. The bonding plate consists of masonite or another rigid plate material. It is fastened to the base to be sealed, after which the sealing foil is fixed to the self-adhesive gum tape.

US Patent No. 3,671,371 discloses a bonding plate system wherein a thermoplastic foil is fastened by thermal welding, using high-frequency equipment, to a metal plate coated with a thermoplastic layer, which is fastened to the underlying structure.

European Patent No. 0 344 523 discloses a bonding piece system wherein several magnitudes, such as dimensions, elasticity, tensile strength, thickness etc. of various parts and their relations to each other are laid down exactly. The system comprises a round or square bonding piece, which is fastened to the base by means of a washer and a linear fastener. A glue may be applied to the bonding piece and to the washer, or the bonding piece may already be provided with a pressure-sensitive self-adhesive tape, from which the protective foil is removed. Then an elastomeric sealing foil is glued to and over the reinforced bonding piece. A great many fastening systems are satisfactory for certain applications. It is desirable, however, to have a non-penetrating system by means of which a strong, durable and inexpensive joint can be made in a simple manner. A system, moreover, which is suitable for the highly efficient processing technique of foil membranes. A system which may be used with several foil materials, in particular, however, with the very durable and relatively inexpensive non- reinforced EPDM membrane.

The object of the invention is to provide an improved bonding element fastening system;

- wherein the sealing foil is not penetrated or does not need to be provided with an opening of some kind in order to be fastened to a base, which leads to a reduced number of penetrations of the foil and thus to a reduced risk of leakage.

- wherein the final fixation of the sealing foil, which is preferably in the form of a membrane, to the bonding elements may take place after said foil has been spread out over the base to be sealed and the bonding elements provided thereon, which foil may already be finished at the edges. As a result of this it is easier to process such membranes without creases being formed. The sealing foil is able to perform its sealing functions at an earlier stage of its processing. From a point of view of the amount of labour being required the processing of the membrane may take place more efficiently in this manner.

- which is designed such that its dimensions and shape can be readily adapted to the requirements to be made thereof, without detracting from the essence and unique advantages of the invention. Thus the system may be in the form of for example a bonding-plate, -piece, -strip or -band system or the like.

- which is economically competitive with other fastening systems as regards material costs and processing costs, and by means of which a sealing foil can be fixed quickly and in a simple manner without highly trained personnel being required.

- which may be used in combination with standard fasteners and building materials such as insulating materials, screws, washers, etc; - which is sufficiently resistant against, among other things: possible severe and prolonged moisture conditions; high as well as low and/or varying, possibly prolonged temperature conditions; high, possibly varying, prolonged mechanical loads; possible chemical loads caused by substances from the structure to be sealed.

- which is highly resistant against ageing and which will consequently retain its functional properties at least for the duration of the expected life of the sealing foil.

- wherein the quality of the joint may be checked by optical means, and whereby any faults that become apparent can be corrected in a simple manner without the membrane having to be penetrated or be partially or entirely removed.

- which has a profile which is so low that the fastening system only has a limited effect on the outward appearance of the sealing foil.

- which does not use any welding fluid or bonding medium present at the building site, for: environmental reasons; the solvent contained therein might largely evaporate into the environment. Health reasons; in most cases the solvent is highly inflammable; economic reasons; applying the liquid adhesive medium or the welding fluid at the building site requires a great deal of manual work, under conditions which are often not ideal and which moreover may affect the quality of the joint as well as the health of the operator.

- wherein a joint is made by using certain bonding media, which joint can be broken without damaging the sealing foil. This makes it possible to reuse the sealing foil, in particular an EPDM foil, which is known to have a very long life, if said foil should be prematurely removed from the structure for some reason;

- which enables a practically complete separation of the building materials upon being removed from the structure, without any pollutants of a harmful nature or extent, such as glue or remnants of insulating material etc. , remaining behind, as a result of which it becomes easier to reuse, recycle, incinerate in an ecologically safe manner, or deposit these building materials.

In brief, a fastening system which combines and optimizes the advantages of a great many known systems and adds thereto several new possibilities and advantages, without the limitations and drawbacks of the known systems, however.

In order to accomplish that objective the invention is characterized in that the bonding element is activated by heating it from the side facing away from the underlying structure.

The transfer of heat thereby takes place through the sealing foil.

One embodiment of a method according to the invention is characterized in that said bonding element is activated by placing a heating apparatus on the sealing foil.

One embodiment of a method according to the invention is characterized in that said bonding element is activated by emitting infrared radiation by means of an infrared radiation apparatus, which is disposed at the location of the bonding element without coming into contact therewith.

One embodiment of a method according to the invention is characterized in that the sealing foil is pressed down on the bonding element by means of air pressure when said bonding element is being activated.

A non-penetrating fastening system including a sealing foil and bonding elements is manufactured in accordance with the method according to the invention.

The invention will be explained by way of example below with reference to the accompanying Figures, in which:

Figure 1 is a sectional view of a roof construction, wherein the sealing foil is fastened in accordance with the method of the invention by means of bonding elements of the bonding plate type, showing one of the possible embodiments of the bonding element and the heating element, whereby the head of the fastener projects above the bonding element. The sealing foil is shown in wind-loaded condition and bulges up between the bonding elements, as a result of which the joint between bonding elements and sealing foil is loaded for peel.

Figure 2 shows a construction similar to the one shown in Figure 1, with this difference that the head of the fastener is recessed in the bonding element, that the heating element is flat on the underside and that the sealing foil is shown in unloaded condition.

Figure 3 shows a fastening method as shown in Figures 1 and 2, wherein the underlying structure is provided with a soft and compressible thermal insulating material, and wherein the bonding element is fitted with a socket to allow the screw to slide within said socket if the bonding element should be pressed into the insulating material. Figure 4 shows a construction similar to the one shown in Figure 3, with this difference that the bonding element is recessed in the thermal insulating material.

Figure 5 is a sectional view of a roof construction, wherein the sealing foil is illustrated in unloaded condition and is fastened in accordance with the method according to the invention, in contrast to the preceding Figures, however, the sealing foil is in this case fastened by means of a bonding element of the bonding piece type instead of being fastened by means of a bonding plate. Figure 6 shows the same construction as shown in Figure 5, with this difference that the construction is shown in wind-loaded condition in this Figure, with the joint between bonding piece and sealing foil loaded for shear.

Figure 7 is a view of a bonding element as shown in Figures 5 and 6, with a washer being mounted under the bonding element. Figure 8 shows a bonding element according to the same principle as shown in Figure 7, wherein the construction of bonding element and washer allows the use of a flat heating element.

Figure 9 is a perspective sectional view of a part of a roof construction and a heating element, in which the sealing foil is fastened by means of the method according to the invention.

Figure 10 is a view corresponding with Figure 9, with this difference, however, that strip-shaped bonding elements are used.

Figure 1 shows one of the possible embodiments of the fastening system as aimed at by the invention. The Figure shows a construction 1 to be sealed, on which a disc-shaped bonding element 2 has been fastened to the underlying structure by means of a screw 3 as a linear fastener.

Following this a sealing foil 4, for example a 1.2 mm thick EPDM foil, has been spread out thereover. The material of said bonding element 2 is a HDPE polymer. In this embodiment the HDPE material of said bonding element functions to transmit the forces acting on the sealing foil to the linear fastener, whilst it also functions as an adhesive medium. The fixing of the sealing foil 4 to the bonding element 2 subsequently takes place by pressing sealing foil 4 firmly down on bonding element 2 for a short time (± 40 sec.) by means of a metal heating element 6 of ± 200 °C, which is precisely centred with respect to the sealing element under sealing foil 4 and with respect to screw head 5. Under normal processing conditions the heat of heating element 6 will propagate via conduction within said 40 seconds by heating the 1.2 mm thick (for example) EPDM foil material and the surface of the HDPE bonding element 2 to about 200 °C, taking into account heat losses. At this temperature the HDPE is in its melting stage, in this condition HDPE is capable of entering into combination with EPDM, provided both materials are also pressed together firmly for some time. Once the joint that has been formed has cooled down, after the heating element has been removed from the foil, the joint is capable of taking up high mechanical loads. Heating element 6 (Figure 1) is provided with a recess 8 for receiving the thickening in the foil caused by the head 5 of screw 3 when foil 4 is pressed down on bonding element 2 by heating element 6. A joint between foil 4 and bonding element 2 is only formed around screw 3, where the heating element 6 presses the foil 4 down on the bonding element 2. The foil material 4 is thereby elastically deformed over head 5 of screw 3 by heating element 6. Heating element 6 must be precisely centred with respect to the head of screw 3, in order to prevent foil 4 from being damaged as a result of getting wedged between heating element 6 and screw head 5 and in order to be certain that heating element 6 provides a good contact between foil 4 and bonding element 2.

A polymer which inter alia has the advantage of being capable of entering into molecular combinations is the bonding polymer LLDPE, which is inter alia produced by DSM under the brand name parex. Parex moreover appears to be quite capable of entering into combination with a number of other synthetic materials, ceramic materials and metals.

It is also possible to manufacture a bonding element of a material which is more suitable from for example a mechanical or constructional point of view, but which does not have properties that can be thermally activated to make the element adhere to the sealing foil, and subsequently apply a suitable bonding medium, for example LLDPE, to said element.

The bonding elements shown in Figures 1, 2, 3 and 4 are all made of a rigid material and are of the so-called bonding plate type. The drawback of bonding plate systems is that the joint 22 (see Figure l) between the rigid bonding plate 2 and the flexible elastic sealing foil 4 is loaded for peel when the foil bulges up between the bonding elements as a result of the wind load. A joint loaded for peel is not capable of taking up mechanical loads of the same magnitude as a joint loaded for shear and as a consequence it will fail sooner (Figure l; 23) .

Figures 5, 6, 7 and 8 show possible embodiments of a bonding element according to the bonding piece principle. Figure 6 shows that the joint 24 moves upwards along with the sealing foil 25 when said foil bulges up as a result of the wind load. A joint of this type is only loaded for shear and is capable of taking up much larger forces. The material of the bonding piece must have the combined properties of being highly flexible, having a great mechanical strength and a low elasticity; moreover it must adhere well to the bonding medium and inter alia be capable of withstand the thermal load caused by the thermal activation of the bonding medium.

The bonding piece 26 (Figures 5 and 6) consists of a flexible disc of EPDM foil, which has a thickness of for example 2 mm and a diameter of for example 100 mm, with an inlay of polyester tissue as the reinforcing material. At its side facing the sealing foil the bonding piece 26 is provided with an adhesive medium 27, namely the adhesive polymer Yparex (LLDPE) . The bonding piece coated with bonding medium is fastened to the underlying structure 30 and to base 31 by means of a suitable washer 28 having a diameter of ± 40 mm and a screw 29. An EPDM sealing foil 25 having a thickness of for example 1.2mm is spread outthere over. The bonding of the sealing foil to the bonding element takes place according to the same principle as described before.

To this end heating element 32 is centred at the location of the bonding piece with respect to the washer covered by foil, and presses the sealing foil surrounding said washer down on the bonding element.

In another embodiment of the bonding element (Figure 2) screw 10 is recessed relative to surface 11 of bonding element 12. This makes it possible to make the underside of heating element 13 flat, and thus excluding the aforesaid risk of the foil 14 being damaged as a result of getting wedged between the heating element and the screw head; the heating element need not be centred so precisely with respect to bonding element 12 and screw 10.

In yet another embodiment of the bonding element (Figure 3) the underlying structure is provided with a soft compressible material (for example a rockwool insulating material 43 or the like) . There is then the danger that when a bonding element as shown in Figure 1 or 2 is used on a base of this type, such a bonding element is pressed into said material when the sealing foil is loaded (for example by the weight of a person walking thereon or otherwise) , and that the screw anchored in the underlying structure will penetrate the sealing foil or damage said foil otherwise. That is why the bonding element (Figure 3) is fitted with a socket 17, in which screw 18 can slide up and down when the bonding element is pressed into the base. The head of the screw is recessed so deeply in the socket that the risk of the foil being damaged by said head can thus be excluded.

In yet another embodiment of the bonding element (Figure 4) , bonding element 19 can be partly recessed in the base consisting of thermal insulating material 20, which results in a lower profile of the bonding element relative to the base, whereby the bonding element stands out less markedly against foil surface 21. At the same time this reduces the risk of tripping over the bonding element and/or the risk of damage to the foil, due to an improved connection between foil and base, resulting in a decreased dead volume between the two and an enhanced suction cup effect between sealing foil and base.

For several reasons the combination of a polymer, such as for example PE as the adhesive medium, and EPDM foil as the sealing material appears to be a good match, inter alia because: EPDM is an elastomer; it does not have a melting phase and is capable of withstanding elevated temperatures. It has become apparent that the temperature of ± 200 °C required to effect a bond between the two materials does not affect the technically relevant functional properties of the EPDM sealing foil. The bond between the two materials is based on an intermolecular combination, which is chemically, thermally and mechanically very stable within the technically relevant field and which is capable of withstanding very high mechanical loads.

As a result of this the heat of the heating element will penetrate through the sealing foil to the adhesive medium and heat said medium to ± 200 °C. At this temperature the adhesive medium will inter into molecular combination with the EPDM foil and thus connect the sealing foil to the underlying structure via the bonding element, the washer and the screw. Tests have shown the bonding element to be capable of taking up a load of over 1300 N.

Figure 7 shows another embodiment of a similar type of bonding piece element, with the difference that in this embodiment a disc of a rigid material 33 is mounted under the bonding piece, the washer and the screw. Said disc provides the adhesive piece with a flat base, as a result of which there will be a good contact between the heating element and the sealing foil when the former is pressed down on the latter. The disk furthermore functions as a heat screen for the materials of which the base is built up. The disc may furthermore be used for fastening the thermal insulating material 34 provided on the underlying structure, whereby the relatively large diameter of the disc is a favourable factor when fastening insulating material having a low critical compressive strength.

Figure 8 shows yet another embodiment of a bonding piece element, with a disc 35 fitted thereunder. In this embodiment the disc and the other components of the system are configured such, however, that the adhesive medium 37 present on bonding piece 36 projects above the other components of the bonding element, such as screw 38 and washer 39. The advantage of this over the element of Figure 7 is inter alia the fact that heating element 40 can be centred more easily with respect to the bonding element so as to fix the foil.

Although the above description mainly mentions thermoplastic polymers, such as for example HDPE, and special bonding polymers, such as for example LLDPE as the adhesive medium, this does not mean that the scope of the present invention does not include the use of other suitable adhesive media which are capable of being thermally activated. Although the preceding descriptions only mention a single disc-shaped element which is fastened with a single screw, possibly in combination with a washer, it will be apparent that a fastening system will usually be built up of a number of fastening elements which is attuned to the load to be expected (see Figures 9, 10 and Figures 1 - 8, which may be considered to be sectional views of bonding element 41 and 42 in Figure 9 and 10) , which fastening elements are preferably fitted in a regular pattern in regularly spaced- apart relationship. Furthermore it will be apparent that the bonding element and the washer that is possibly used do not necessarily have to be round, they may also be polygonal or strip-shaped (Figure 10) , for example, or the like, and a single bonding element may be fastened to the underlying structure by means of several fasteners. Furthermore the fastener does not necessarily have to be a screw, any other fastener or technique may be used, if suitable, for fastening the bonding element to the underlying structure. Furthermore the sealing foil and the bonding piece do not necessarily have to be made of EPDM, any other suitable combination of sealing foil, adhesive medium, bonding piece or bonding plate falls within the scope of the present invention.

Although the preceding descriptions only mention a rigid metal heating element having a shape and construction which depends on the shape and construction of the bonding element, any other thermal activation and compression method wherein the supply of the activating heat for the adhesive medium and the pressing down of the sealing foil on the bonding element takes place from the side of the sealing foil facing away from the bonding element and wherein said activating heat propagates through the foil to the adhesive medium will fall within the scope of the present invention. The preceding descriptions largely deal with fastening systems for fastening EPDM roof membranes. It will be apparent to every person skilled in the art, however, that the great advantages and new applications which the present invention provides, not only relate to a single particular field of application. Consequently the preceding descriptions and drawings are only given by way of illustration and by no means exclude other combinations of materials, constructions, brands and/or applications for which the same unique fastening principle as the one being claimed may be used.

Claims

C A I M S

1. A method for fastening a sealing foil to an underlying structure, comprising the steps of providing bonding elements on or in said underlying structure and subsequently providing said sealing foil, characterized in that said bonding element is activated by heating it from the side facing away from the underlying structure.

2. A method according to claim 1, characterized in that said bonding element is activated by placing a heating apparatus on said sealing foil.

3. A method according to claim 1, characterized in that said bonding element is activated by emitting infrared radiation by means of an infrared radiation apparatus, which is disposed at the location of the bonding element without coming into contact therewith.

4. A method according to claim 2 or 3, characterized in that said sealing foil is pressed down on the bonding element by means of air pressure when said bonding element is being activated.

5. A bonding element to be used in a method according to claims 1 - 4.

6. A non-penetrating fastening system comprising a sealing foil and bonding elements obtained by using the method according to claims 1 - 4.