Brief Description of Prior Art Normally, sandwich panels are used for walls. On that occasion, the sheet surfaces are normally even, both on the inside and on the outside or have a very low profile configuration, e. g. at most 1 mm in depth. The side edges are formed with male and female parts that mate and are sealed by a jointing. Attempts have been made to adapt the elements for roofs by replacing the female and male part on the top side by sheet laps that are fold together at site or have a simple overlapping hook. The solutions are not good from mounting or tightness point of view. Increasing projecting sheet edges in order to achieve a safer side lap has the disadvantages that the sheet consumption becomes greater, which limits the width that the panels can be manufactured into, and also that said projecting sheet edges run the risk of becoming damaged in transportation and mounting, which causes risk of leakage.

Normally, a profiling of the inner parts of the upper sheet surface is also desired from an aesthetic point of view. The profiling causes increased sheet consumption per unit of width, which means that the panels have to be made even narrower for a given sheet width.

Another problem is that through screws for attaching the panels to subjacent supporting structure do not become tight against water. The reason is that the panels are somewhat compressed by the load and the screws losing clamping force. On that occasion, water may run in under the screw head and washer. In order to avoid this, frequently the screws are placed countersunk in the proper side joint between the panels by means of a particular thin sheet metal that is hitched in the outer sheet surface of the panel mounted first. The construction is complicated, expensive and weak and furthermore it limits the screw distances to the dimension of the panel width, which may be too large for carrying occurring forces.

The Object of the Invention and a Brief Description of the Invention It is an object of the invention to avoid the disadvantages mentioned above and to provide a roof construction of the kind to which the invention pertains, that has considerable safety against leakage.

This is fulfilled by the upper metal sheet of the panels having ridges along the edges thereof and being attached to transverse beams by through fastening elements applied through the upper metal sheet on the outside of the ridges, as well as by a longitudinal cover sheet being arranged to cover the joint between two adjacent sandwich elements as well as said ridges close to the joint.

In this way the fastening elements, which usually are screws, are covered. Even if the cover sheet subsequently is bolted, said screws will not be unsafe to the tightness in the same way since they bolt the cover sheet directly against a subjacent sheet. The risk of such screws that clamp together two sheets giving rise to leakage is negligible, but the possibility remains to use a sealing compound between the sheets in the areas around the screws.

Brief Description of the Drawings Figure 1 shows in cross-section two adjacent sandwich elements in a roof construction according to the invention.

Figure 2 shows enlarged the area around the joint between the sandwich elements in figure 1.

Figure 3 corresponds to figure 2, but shows the joint between the sandwich elements upon completion.

Detailed Description of Shown and Preferred Embodiment Example In the figures, a roof construction is shown with sandwich elements 11,12 put up on transverse beams 13 so that they lie in the direction of the slope. Only two adjacent sandwich elements are shown to illustrate how the sandwich elements are jointed by joints in the direction of the slope. The sandwich elements consist of an insulating core 14 of, for instance, hard mineral wool or polystyrene, and sheets 15,16 are glued to both sides of the core.

The sandwich elements are attached to the subjacent beams 13 by fastening elements 18-21, usually screws as are shown in figure 1. Normally, the distance between the beams 13 can be 3-4 m. Each element has a bulge or ridge 22,23 at each longitudinal edge close to the same, and the screws 18-21 are placed outside the bulges or ridges 22,23, i. e. , between the bulge and the edge of the element, as is most clearly seen in figures 2 and 3.

A cover sheet 30 is most clearly shown in figures 2 and 3. It has a bulge or ridge 31, 32 at each edge and these bulges are adapted to cover the bulges 22,23. Hence, the cover sheet covers the joint between the elements 11 and 12 and the fastening elements 19,20 on each element. The fastening elements are protected against ingress water by the bulges 22,23 of the elements.

The cover sheet 30 can be screwed to subjacent upper sheets 15,16 on the elements by screws 27,28. Suitably, the bulges of the cover sheet are screwed directly against the bulges of the elements, as is shown. Such a screw that clamps together two closely lying sheets, does not normally involve any risk of leakage. As is shown, suitably the bulges 22,23 of the elements can be narrower than the bulges 31,32 of the cover sheet and the securing screws 19,20 can be attached close to the element bulges. Thereby, the securing screws 19,20 need not to be countersunk in the upper sheet surface of the panels 11,12, even if the surface of the cover sheet 30 connects directly against the panels 11,12 Accordingly, the securing screws 19,20 are covered by the cover sheet 30 and thereby the risk of leakage is decreased. Since the securing screws are screwed through the insulation, a resilience can be obtained, for instance upon snow load, which otherwise would cause risk of leakage around the screw heads.

From an aesthetic point of view, it could be advantageous to have bulges 33-36 of the same aesthetics as that of the bulges 31,32 of the cover sheet 30 and of the same spacing so that a uniform aesthetics of the roof is obtained, which thereby makes the joints between the elements hardly visible.

Since the upper sheet 15 has bulges, it becomes somewhat narrower than the bottom sheet 16 if the same reel of strip is used for crown sheet and bottom sheet. By covering the joint by a relatively wide cover sheet, it is, however, possible to have a crown sheet that do not cover the entire width of the element but leaves a narrow edge of the insulation uncovered. In such a way, the width the lower sheet 16 can be utilized fully out as the element width.

The lower sheet 16 of the elements has a female part and a male part so that two elements should mate and provide tightening from below at 37 in figure 3, in order to decrease the risk of condensation in the joint.