In the design and detailing of a wall there is much scope for initiative, ingenuity and individuality. Many types of wall are possible and all will perform satisfactorily provided the basic requirements are met. One possible solution is as follows:
The principal structural wall element will be a quality product of precast concrete. In conformity with the new, scientifically sound approach to the design of walls it will be located on the inside of the total wall complex. Any minor surface blemishes can be touched up either before or after erection to provide an internal face acceptable for decoration. Painting with a heavy-bodied paint or papering the inner face will further increase the airtightness of the panel itself so that the problem of producing an airtight and visually acceptable internal face to the wall will be confined to the joints.
Now that this main element of the wall is located in a warm and thermally stable environment, it is possible to integrate it with the structural system of the building. It is beyond the scope of this Digest to discuss the methods of doing so, but some possible systems can be mentioned briefly. With office-type buildings lateral stability can be obtained from a cast-in-place central elevator core. The wall panels can be stabilized from this core by means of the floor, which can be either cast-in-place or precast. With apartment-type buildings, stability can be obtained from the interior walls, which can be precast as is done in many European types of "system" building. Moment connections between precast elements are more difficult to achieve, but are used in some cases.
The external cladding can be made of thin precast concrete panels of high quality, with possibly only a single connection projecting from their inner face. This connection passes through the insulation to be embedded in the concrete of the main wall panel as it is cast against the back of the insulation. Air spaces between the insulation and the main panel are thus eliminated and no special adhesive is needed. Assembling the cladding on the main panel before erection also minimizes the number of site activities required.
The external cladding panel can be free of all but the most minor cracks and, since it is free to expand and contract, stresses will not be induced that might cause these to open further. The panel can be taken as essentially impervious and special measures for the control of rain penetration can be confined to joints. The natural lack of fit between the insulation and the roughly screened back of the face panel will, however, provide some space for pressure equalization, and for drainage if necessary. Alternatively, the back can be contoured in sympathy with the external face.