Loads can be transferred onto wall panels that were not designed to be load-bearing if inadequate clearance is allowed to accommodate not only the movements that take place but also the variations in the size of the panels within the manufacturing tolerance. In particular, allowance must be made for the shortening of a concrete structural frame and the deflection of horizontal spanning members (CBD 54) under the action of elastic stress, drying shrinkage, and creep under sustained load. Transfer of load in this manner can lead to displacement of the panel or to cracking and spalling.
Sandwich-type panels, with the insulation located between two leaves of concrete, have many advantages but they present special difficulties. The two leaves of concrete will be subjected to different conditions and so will have different expansions and contractions. Should they be rigidly connected there is a possibility that the connectors will be sheared off or that the panel will crack or become bowed. Cold winter temperatures would make the exterior leaf contract in relation to the interior one, thus making the panel concave on the outside. From examination of panels in service this does not appear to be the critical factor, since all that had bowed were concave on the inside and there were more cracks in the inner leaf than in the outer. It would seem, therefore, that drying shrinkage of the inner leaf is of greater importance in causing this problem than temperature difference.