however possible for the dimensioning of both types of main girder 4 5 to differ the primary sub girders 6 are subsequently arranged this such that in each sector 8 bounded by a primary main girder 4 and a secondary main girder 5 they extend from the secondary main girder 5 substantially parallel to the primary main girder 4 the mutual distances between the primary sub girders 6 are equal to the distance between primary main girder 4 and the closest primary sub girder 6 finally secondary sub girders 7 are arranged which extend parallel to the closest secondary main girder 5 the primary sub girders 6 are herein intersected from considerations of dimensioning the distance between the secondary sub girders is equal these primary sub girders are not however essential for the present invention they may be omitted when the construction has sufficiently small dimensions shown in fig2 is an embodiment of the invention wherein tertiary girders 14 are arranged between the joints of primary and secondary girders these tertiary girders 14 extend substantially in tangential direction relative to the centre these tertiary girders thus form polygons centered round the centre dimensioning requirements for the primary and secondary girders are hereby lessened such a construction is known as a dome rod like elements are herein often used as girders the actual cladding of the construction is subsequently arranged in the form of zigzag folded strips 9 the width of these zigzag folded strips 9 is slightly greater than the distance between two primary sub girders respectively the distance between.