Essentials of

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Part 2--Construct a Concrete-Block Wall


Buildings are constructed with various sizes and kinds of concrete blocks that can be hollow or solid. The different types of blocks are made with heavyweight or lightweight materials and are normally referred to as such.

2-3. Actual and Nominal Sizes. Concrete blocks come in specific sizes. The 3/8-inch mortar joint has been adopted as the standard-size joint for joining blocks. The actual dimensions of the block are fractional; when combined with a 3/8-inch mortar joint, the dimensions will come out even in inches or nominal sizes. Therefore, a 15 5/8-inch stretcher block with a 3/8-inch mortar joint equals 16 inches. The same explanation holds true for heights and widths.

2-4. Typical Sizes and Shapes. Blocks come in both heavyweight and lightweight materials with full- and half-length sizes. The three-core block can also be obtained as two-core blocks. Figure 2-1, illustrates some of the typical sizes and shapes of concrete blocks.

Figure 2-1.  Types of concrete blocks
Figure 2-1. Types of concrete blocks

Figure 2-1.  Types of concrete blocks (continued)
Figure 2-1. Types of concrete blocks (continued)

2-5. Types. Concrete blocks come in several different types.

a. Stretcher. A stretcher block is the most commonly used block in construction. It is laid with its length parallel to the face of the wall.

b. Corner. A corner block is used for corners at simple window and door openings.

c. Double Corner or Pier. A double-corner or pier block is used for constructing piers pilasters or for any other purpose where both ends of the block would be visible.

d. Bull Nose. A bull-nose block serves the same purpose as a corner block, but it is used where round corners are desired.

e. Jamb. A wood-sash jamb block is used with a stretcher and a corner block around elaborate window openings. The recess in the block allows room for the various casing members, as in a double-hung window.

2-6. Most Common Block. The most common concrete block is the hollow, load-bearing stretcher block, which is 8 by 8 by 16 inches nominal size, but 7 5/8 by 7 5/8 by 15 5/8 inches actual size. The heavyweight load-bearing stretcher block weighs from 40 to 50 pounds.

Note: In Figure 2-2, the cores taper toward the top of the block, providing a wider face shell. Always lay this block with the wider face up to allow for a greater area on which to lay a bed of mortar.

Figure 2-2.   Hollow load-bearing stretcher block
Figure 2-2. Hollow load-bearing stretcher block



David L. Heiserman, Editor

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Revised: June 06, 2015