The site-cast building technique can best be described in terms of actual projects in which it has been used. Buildings utilizing this system have been built near Redwood City, California, by Challenge Developments, Inc. Panel stacks are laid out around the perimeter of the foundation slab in such a manner as to provide two completely encircling sets of stacks of wall and floor panels separated by a 24 to 27 foot wide aisle. This aisle is used initially by the various trucks, including concrete trucks, and later, during the erection process, by the mobile crane. A rigger's layout is provided by the architect to show the location of the stacks. A slab schedule describes each panel in each stack, its location, lifting sequence and final position in the building. To avoid errors that could seriously affect construction costs, every panel is detailed in shop drawings and field checked by a representative of the architect. Thin concrete casting beds are carefully laid out and placed to provide a foundation on which subsequent panels can be fabricated. Panels are cast one on top of another, with as many as fourteen to sixteen in a stack. The panels to be lifted last are cast first, a necessity if unnecessary movement of panels is to be avoided. At first concrete may be deposited directly from ready mix trucks, but when the height of the stack reaches approximately five feet a pump is used to lift the concrete to the desired height. Concrete is placed conventionally and vibrated in a flat position in the same manner as it would be for a sidewalk or a floor. The finish is power-troweled and then touched up by hand. The key to erection efficiency is preplanning. A crane modified to provide 100 ton capacity is used. The California builder has suggested that additional economies might result from use of an even larger crane, primarily because it would decrease the number of moves by increasing the reach. The construction cycle for buildings constructed using the site-cast technique can be quite attractive to investors. The relatively large buildings described here required only nine months from ground breaking to completed building ready for move-in.