Abstract: A module for a construction system is disclosed which can be used to form building panels and three-dimensional structures that may include self-supporting cladding. In one form the basic module (10, FIG. 1A, drawing ?e!) is formed from two pleated hexagonal plates (11a and 14a) joined together at their peripheries with their concave sides together and with the ridges on one opposite the valleys of the other. Each plate is formed from a blank (11 and 14, respectively) which is a hexagon distorted by extending the radii which will form the valleys of the plate with respect to the radii of a regular hexagon (drawings ?a! and ?b!).