Abstract: Two panels respectively of concrete and insulating material form a prefabricated wall and are maintained in relatively spaced relation so as to form an air gap by means of coupling anchors. Each anchor head which is remote from the end to be embedded in the concrete panel is provided with notches for resilient engagement of the fastening flanges of a U-section retaining member mounted astride a row of anchor heads. The coupling anchors are disposed in planes at right angles to the axis of the retaining member.