Trapezoidal roofing insulating or bridge profile

The webs (3) are profiled to compensate for the difference in length between the top and bottom flanges (2,4) so a concertina web shape opens at dissimilar angles to accommodate for this length difference. The web can also be undulated in profile in which case it uses dissimilar radii for this purpose and the top and bottom flanges may be themselves grooved tangentially in the longitudinal direction or else may be undulated in the same direction. In a further variant, the web may be composed of several profile parts to form an asymmetric or symmetric profile overall. Top and bottom flanges and their web can be produced separately or together, in which case the top flange and web may be made together and the bottom flange (4) made separately, using compensated length difference and connecting joins to give the trapezoidal end product.