When mounting roof windows and other kinds of roof penetrating building structures in a roof surface, watertight joining of the building structure in ques- tion to the roof covering is normally established by means of a flashing which is secured, on one hand, to the exterior sides of the roof penetrating building structure, e. g. the frame structure of a roof window, said exterior sides being substantially perpendicular to the roof surface, and, on the other hand, is brought into the best possible, watertight connection with the surrounding roof covering.

In case of roof windows having a rectangular frame structure, such a flashing typically comprises a top member, two side members and a bottom member to be secured to the top, side and bottom members of the frame structure, and a predominantly strip-shaped, manually easily deformable skirt member, which at its one longitudinal edge is brought into watertight connection with the bottom member of the flashing, the second longitudinal edge of the shirt being, due to the easy manual deformability, formed and pressed down into the best possible abutment against the roof covering below the bottom member of the window.

Particularly in case of roof coverings of materials showing comparatively big differences in level, like for instance tiles, it is commonly known to use skirt members manufactured with a built-in material surplus, for instance from corrugated or plaited

materials, to facilitate the adaptation to the shape of the roof covering.

In connection with such roof coverings it may be difficult, however, to retain the free edge of the skirt member in a sufficiently tight abutment against the subjacent roof covering.

On one hand, both during handling on the building site and later at the mounting of a roof window in connection with adaptation of the tiles placed around the window, the skirt member is subjected to repeated deformation impacts in the form of bending, which in respect of some flashing materials, e. g. aluminium, may cause a cold setting, which counteracts the intended manual deformability and impedes the final shaping and pressing down of the skirt member in abutment against the roof covering.

Even by non-problematic mounting, the free lower edge of the skirt member may, due to heavy wind impact on the roof surface, be pressed up from the roof covering, so that the desired watertightness of the connection is reduced or eliminated.

To counteract these problems, attempts have been made to apply various types of adhesive coverings to the lower part of the skirt member at the free edge to establish an adhesive retainment of the skirt member to the roof covering, which may for instance consist of tiles.

In addition to complicating and making the manu- facture of the skirt member more expensive, this solution suffers in practice from the drawback that the mounting cannot be performed when it is raining or when the outside temperature is below approximately 5°C.

The object of the invention is to remedy the above-mentioned drawbacks and to ensure retainment of an easily deformable flashing skirt member in sealing

abutment against a roof covering, so that penetration of drifting snow or heavy rain under the skirt member is substantially prevented, the mounting work being not complicated to any substantial extent or limited to being carried out under certain, favourable climatic conditions.

To meet this object, a fastening device of the kind in question is according to the invention charac- terized by comprising a strip member of comparatively short length and designed at one end to be secured to the roof covering and, at the other end, to press down the free edge of the flashing skirt against the roof covering, and a securing means for securing said one end to the roof covering.

When mounted, the fastening device according to the invention will have the effect of a clamp which in practice has proved effective in retaining a skirt member as described in the desired sealing abutment against the roof covering.

Preferred embodiments of the fastening device are stated in the dependent claims.

The invention will now be explained in detail in the following with reference to the schematic drawing, in which Fig. 1 shows an embodiment of a fastening device according to the invention, Fig. 2 is a sectional view showing the securing of the fastening device to a roof covering, Figs 3 and 4 illustrate the mounting of the fastening device for securing the free edge of a deformable flashing member to a roof covering, and Fig. 5 shows an alternative mounting of the fastening device.

In the embodiment in Figs 1 and 2 the fastening device according to the invention comprises a compara-

tive short strip member 1 and a fastening member in the form of a pressure rivet 2 for securing the strip member to a roof covering through a mounting hole 3 at one end of the strip member 1.

The strip member 1 is preferably made from a metallic material having little elasticity and high strength. A suitable material is for instance aluminium foil of a thickness of 0.5-1 mm and having a cor- rosion-proof surface coating.

The pressure rivet 2 is in a manner known per se made from a suitable, elastically deformable plastics material, for instance a thermoplastic elastomer, an with a head 4 having a diameter, which substantially exceeds the diameter of the mounting hole 3 at one end of the strip member 1, and a shaft portion 5 with protruding ribs 6.

As will appear from the sectional view in Fig. 2, the strip member 1 is secured to a roof covering, e. g. roof bricks of tile or concrete, by boring at the protrusions 6 a hole 7 of slightly smaller diameter than the biggest diameter of the shaft member 5, following which the pressure rivet is pressed into the hole 7 through the mounting hole 3 at one end of the strip member 1 for safe retention of said the strip member.

As appears from Figs 3 and 4, the fastening holes 7 in the roof covering are in the embodiment shown placed within the lower edge of the manually easily deformable flashing skirt 8, which may typically be made from pleated lead or aluminium foil with closely packed foldings, the upper edge of which, as shown in Fig. 4, being connected with a flashing member 11 secured to the frame bottom member 9 of a roof window 10.

In the example shown in Figs 3 and 4, in which the roof covering consists of undulated bricks 12 of tile or concrete, the fastening holes 7 are preferably positioned, as shown in Fig. 3, in the wave crests of the roof covering at a distance from the free edge of the flashing skirt 8 corresponding for instance to approximately half of the length of the strip member 1.

After securing of each strip member 1, the bottom edge of the flashing skirt 8 is pressed down into abutment against the roof covering and the strip members secured thereto, following which, as shown in Fig. 3, the second end of each strip member 1 protrud- ing from under the lower edge of the flashing skirt 8 is bent approximately 180° for producing a clamp, which, as shown in Fig. 4, ensures a stable securing of the lower edge of the flashing skirt 8 to the roof covering.

Alternatively, as shown in Fig. 5, the fastening device according to the invention may comprise a strip member 1'of an elastically deformable material having a spring effect, for instance sheet steel. The strip member 1'is hereby secured to the roof covering 12' under the lower edge of the flashing member 8'and is designed in such a manner that it forms a resilient loop intended for pressing down the strip member against the roof covering.