Copyright Goodheart-Willcox Co., Inc. Chapter 14 Wall Systems 293 Green Note Precast Concrete—Upcycling and Downcycling In upcycling, waste materials are used to provide new, high-quality products. Precast concrete can be disassembled with a mini- mum amount of energy and retains its original qualities after deconstruction. After removal, precast concrete members can be reused in other applications. Precast concrete can also be downcycled. In downcycling, material is broken down into a material that is useful but of lesser quality than the original. For example, crushed precast concrete can be used as aggregate in new con- crete or as base materials for slabs, roads, and sidewalks. Wall Openings Wall openings can extend through the wall as required for a door or window, or they may take the form of a chase or recess. Chases and recesses are horizontal or vertical spaces left in a wall for the purpose of containing plumbing, heating ducts, electrical wiring, or other equipment. See Figure 14-35. Chases and recesses are formed by masons as the wall is built. Chases are generally located on the inside of the wall and vary in size from 4″ to 12″ in width. Recesses reduce the wall thickness and strength and are usually limited to one-third the thickness of the wall. Code Note Chases The International Residential Code (IRC) spec- ifies that chases and recesses in masonry cannot be deeper than one-third the wall thickness. Lintels A lintel is a structural member placed over an opening in a wall used to support the loads above that opening. Steel lintels should be supported on either side of the opening for a distance of at least 4″. Reinforced concrete lintels should have a minimum bearing of at least 8″ at each end. Gage Brothers in Sioux Falls, SD Figure 14-33. Precast panels form the exterior of this building. Window and doorway openings already have sills and jambs as part of the panels. Gage Brothers in Sioux Falls, SD Figure 14-34. Finished building using brick-clad precast concrete panels.