Concrete masonry units (CMU) are precast concrete blocks that are prefabricated in specific sizes and shapes. Unlike the typical gray concrete blocks used for house foundations or other structural applications, these concrete units are decorative in nature and intended to be seen (Figure 12—66). The exact size of concrete masonry units fluctuates widely among manufactures, although most concrete masonry units are between 4" to 12" wide, 4" to 8" high, and 4" to 8" deep. Some concrete masonry units used for landscape structures are exactly the same as those for pavement. Colors vary, with shades of gray, tan, and brown being most common. The finish also ranges from clean, straight edges to rough, tumbled surfaces. The advantage of concrete masonry
units in comparison to stone or brick is that they cost less and are available in predetermined sizes that are often more easily and quickly installed. Concrete masonry units can be used to:
• construct retaining walls, free-standing walls, and steps.
• fabricate cabinet and fireplace enclosures associated with outdoor kitchens.
• repeat the color and appearance of precast concrete pavers (assuming that a given manufacturer makes both).
• create a uniform color and texture across a wall surface.
• provide colors not available with stone or brick.
Wood is a widely used material for landscape structures because of its availability and relative low cost in comparison to masonry materials. The dimensional sizes of wood used in landscape structures vary more widely than sizes of wood used for pavement. In addition, wood possibilities include plywood, tongue-and-groove material, and cut wood for posts, caps, and rails. Most wood used for landscape structures is pressure – treated wood, especially if it is in contact with the ground. Although it is more expensive, cedar is also a good choice of wood because of its natural preservatives that decrease decay. Other types of wood may also be used for structures if they do touch the ground. A distinct advantage of wood is its ability to be painted or stained, thus giving it a wide range of color and finish possibilities. Wood can be employed in landscape structures to:
• construct straight fences of many designs and patterns (Figure 12—67). The lightweight quality of wood and its ability to be easily cut into any dimension give it great flexibility to create fences of various heights, material patterns, and openness (Figure 12—68).
• repeat house colors in the landscape.
• construct trellises and overhead structures of many designs and openness (Figures 12—69 and 12—70).