The site you pick to build your retaining wall should be at the point of the least possible disturbance to the natural slope of the land. It should be where you can build on ground that has never been disturbed rather than where you would build on fill. Because it is easier and less expensive to build lower walls, the location should be where you can design your retaining wall with several low terrace walls rather than a single high wall. This is also a good idea because the design places less strain against low walls than high walls.
Planning for drainage when you build a retaining wall is one of the most essential components in the design. The drainage gets rid of water that would otherwise just build up as it saturates the soil, and it presents several options. The easiest option is simply to build a ditch along the top of the wall to collect surface water. Collecting surface water also can be accomplished by adding evenly spaced weep holes along the retaining wall at ground level. To collect subsurface water, you can build a gravel back-fill that drains off either through weep holes or a drain pipe channeling water into a sewer or other area.
The materials that you choose for building your retaining wall may depend upon your own preference as well as local regulations. So checking your municipal codes before you build the wall is advised. Wood is easier to work with than the much heavier masonry and concrete types of material, and wood also lends the wall a rustic charm. Decay-resistant woods, such as cedar and cypress, or pressure-treated lumber should be used. Wood, however, can present a problem with structural integrity the higher you build the wall.
Poured concrete is the best choice for ensuring structural integrity if you build a water-retaining wall on a steep hillside or on particularly unstable soil. If you want a retaining wall that adds aesthetic beauty to your yard, however, concrete is not an ideal material. Also, the concrete needs to be precisely reinforced with steel.
Railroad ties are often used to create a retaining wall and can be a striking aesthetic choice. The problem with railroad ties is that they are a two-man job at best and require the use of very durable and heavily powered electric tools.
Masonry Blocks and Bricks
Masonry blocks are good for a hilly area that is not so steep that it requires poured concrete. Concrete blocks and adobe block work well when reinforced with steel. Simple house bricks are usually not a good choice unless you need a retaining wall no more than 2 feet high. Otherwise, the pressure may be too much for the mortar joints to withstand. Larger brick walls necessitate the use a double layer of bricks or bricks as a facing on a concrete wall.
Uncut stone is a good choice for a very small and simple retaining wall set on a slight slope. Using this material for larger walls is not a good idea because of a lack of structural integrity and because it is very rough to the touch and heavy to handle.