Sectional views, or sections, provide important information about the height, materials, fastening and support systems, and concealed features of a structure. Figure 2-15 shows the initial development of a section and how a structure looks when cut vertically by a cutting plane. The cutting plane is not necessarily continuous, but, as with the horizontal cutting plane in building plans, may be staggered to include as much construction information as possible. Like elevations, sectional views are vertical projections. They are also detail drawings drawn to large scale. This aids in reading, and provides information that cannot be given on elevation or plan views. Sections are classified as typical and specific.
Figure 2-15.Development of a sectional view.
Typical sections represent the average condition throughout a structure and are used when construction features are repeated many times. Figure 2-16 shows typical wall section A-A of the foundation plan in figure 2-10. You can see that it gives a great deal of information necessary for those constructing the building, Lets look at these a little more closely.
Figure 2-16.A typical section of a masonry building.
The foundation plan shown in figure 2-10 specifies that the main foundation of this structure will consist of a 22- by 28-foot concrete block rectangle. Figure 2-16, which is section A-A of the foundation plan, shows that the front and rear portions of the foundation (28-foot measurements) are made of 12-by-8-by-16-inch CMUs centered on a 10-by-24-inch concrete footing to an unspecified height. These are followed by 8-inch CMUs, which form a 4-inch ledger for floor joist support on top of the 12-inch units. In this arrangement, the 8-inch CMUs serve to form a 4-inch support for the brick. The main wall is then laid with standard 2 l/2-by-4-by-8-inch face brick backed by 4-by-8-by- 16-inch CMUs.
Section B-B (figure 2-17) of the foundation plan shows that both side walls (22-foot measurements) are 8 inches thick centered on a 24-inch concrete footing to an unspecified height. It also illustrates the pilaster, a specific section of the wall to be constructed for support of the girder. It shows that the pilaster is constructed of 12-by-8-by- 16-inch CMUs alternated with 4-by-8-by-16-inch and 8-by-8-by- 16-inch CMUs. The hidden lines (dashed lines) on the 12-inch-wide units indicate that the thickness of the wall beyond the pilaster is 8 inches. Note how the extra 4-inch thickness of the pilaster provides a center support for the girder, which, in turn, will support the floor joists.
Figure 2-17.A specific section of a concrete masonry wall.
Details are large-scale drawings that show the builders of a structure how its various parts are to be connected and placed. Although details do not use the cutting plane indication, they are closely related to sections. The construction of doors, windows, and eaves is customarily shown in detail drawings of buildings. Tyical door and window details are shown in figure 2-18. Detail drawings are used whenever the information provided in elevations, plans, and sections is not clear enough for the constructors on the job. These drawings are usually grouped so that references may be made easily from the general drawing.
Figure 2-18.Door and window details.