Tilt-up construction basically involves job-site prefabrication of concrete building members under controlled and relatively economical conditions. Numerous design options are available in this method of construction. Wall panels can be either load-bearing or non-load-bearing. The joints between panels can be minimized or used for decorative purposes depending on the design chosen. Load-bearing tilt-up wall panels provide good support for roof systems and also may act as shear walls. The panels are erected first, then the joints or beams are attached to them. At the base a continuous floor-edge strip is cast, with connecting dowels to tie the panel to the floor-edge strip with connecting dowels to tie the panel to the floor for lateral support. These panels are usually wielded together along the sides and at the top. Where the floor to panel connection is not used lateral support may be supplied by pilasters. Non-load-bearing tilt-up wall panels are used to enclose a building frame and also may act as a shear wall. They are connected to the columns with rebars or weld plates and sometimes are bolted or welded to the roof. The most common tilt-up procedure is to erect exterior walls first, followed by the roof framing system. Where a shell roof is constructed first, the panels are attached to the shell and at the base. A wall panel of sandwich construction may be preferred for many buildings. Sandwich panels consist of two thin shells of high strength concrete bonded to a core of rigid, low density insulation. In sandwich construction, the outer face should be high quality concrete. Reinforcement must be provided in the shells and shear connectors between the outer shells. Sandwich panels are not normally used as load-bearing walls.