Buildings consist of both "structural" and "nonstructural" components. The distinction between the two types of building components is described below.
The structural components of a building resist gravity, earthquake, wind, and other types of loads and typically include the following elements:
- vertical supports such as columns, posts, pillars, and pilasters
- horizontal supports such as trusses, girders, beams, joists, and purlins
- load-bearing walls that provide vertical support or lateral resistance
- diagonal elements such as braces
- floor and roof slabs, sheathing or decking
- foundation systems such as slabs on grade, mats, spread footings, or piles
The structural system of buildings is typically analyzed and designed by a civil or structural engineer and is presented on construction drawings or plans, except in the case of houses. The structural components of a typical building can be seen on Figure 2.1.2-1.
The nonstructural components of a building include all building parts and contents except for those previously described as structural. These components are generally specified by architects, mechanical engineers, electrical engineers, and interior designers. However, they may also be purchased and installed directly by owners or tenants after construction of a building has been completed. In commercial real estate, the architectural and mechanical, electrical, and plumbing systems may be considered a permanent part of the building and belong to the building owner; the furniture, fixtures, equipment and contents, by contrast, typically belong to the building occupants.
In this guide, nonstructural components are divided into three broad categories:
- Architectural Components such as partitions, ceilings, storefronts, glazing, cladding, veneers, chimney, fences, and architectural ornamentation.
- Mechanical, Electrical, and Plumbling (MEP) Components such as pumps, chillers, fans, air handling units, motor control centers, distribution panels, transformers, and distribution systems including piping, ductwork and conduit.
- Furniture, Fixtures, and Equipment (FF&E), and Contents such as shelving and book cases, industrial storage racks, retail merchandise, books, medical records, computers and desktop equipment, wall and ceiling mounted TVs and monitors, file cabinets, kitchen, machine shop or other specialty equipment, industrial chemicals or hazardous materials, museum artifacts, and collectibles.
The list of nonstructural components is nearly endless and constantly evolving, as new technologies alter our built environment. Figure 2.1.2-1 displays a typical building with nonstructural components discussed in this document, along with typical structural components. Clicking the “structural components only” button strips away the layer of nonstructural components to emphasize the ubiquity of architectural, MEP, and FF&E components in the built environment.
Note that most structural components are typically concealed from view by nonstructural materials, such as architectural finishes. For example, in steel construction, fireproofing is typically applied directly to steel members and then covered with finish materials such as gypsum board. In wood construction, there is usually no way to visually distinguish between a non-load-bearing partition and a structural or shear wall. Steel diagonal braces are often hidden inside walls. Similarly, mechanical, electrical, and plumbing components are also typically concealed by architectural components.
In general, the structural components of a commercial building account for approximately 15–25% of the original construction cost, while the nonstructural (mechanical, electrical, plumbing, and architectural) components account for the remaining 75–85% of the cost. Contents belonging to the building occupants, such as movable partitions, furniture, and office or medical equipment, represent a significant additional value at risk. When these costs are compared, it becomes clear that the largest capital investment in most commercial buildings is in the nonstructural systems and contents. This is illustrated in Figure 2.1.3-1 below for three common types of commercial construction (Whittaker and Soong, 2003).