Wooden retaining walls can be made from different types of wood that are designed for strength, durability, and resistance to water damage. Pressure-treated lumber can be used for walls that will be in regular contact with moisture, though this can be more expensive than other types of wood. Untreated wood can be used for wooden retaining walls, but steps will need to be taken to ensure the wood is somehow waterproofed; waterproofing will probably need to be applied yearly. Railroad ties can also be used for wooden retaining walls, though these can be somewhat difficult to work with because of their weight and composition.
Cedar timber is a great choice of material for wooden retaining walls, though cedar can be somewhat more expensive than other types of wood. Cedar is a popular choice because it is naturally resistant to water damage, and it will resist bug infestations as well as molding and mildew. The naturally beautiful look of cedar also makes it a popular choice. Unlike other types of lumber, cedar will not need to be chemically treated, though after several years of exposure to the elements, it may begin to fade.
Railroad ties are sometimes used to build wooden retaining walls. Railroad ties are strong, but they are also very heavy and difficult to manipulate. They tend to splinter, and they contain significant amounts of creosote that can be harmful to one's health. If a builder is considering building wooden retaining walls made from railroad ties, he or she should be sure to obtain the railroad ties legally; simply taking them from a railroad yard or property is illegal and punishable by law. Building such a wall will also require more than one builder, since the timbers can be very difficult to move.
Aside from cedar, pressure-treated lumber or timbers is the best option for building wooden retaining walls. Pressure-treated wood is chemically treated to resist damage from moisture and other elements, and it will last significantly longer than untreated lumber. Pressure-treated lumber is probably the most expensive option, however, and many people do not enjoy the look of pressure-treated lumber. Staining or painting may be necessary to improve the aesthetic appeal of the wall.
The specific design of the wall will vary according to the function and location of the wall. Each retaining wall will be different, since every yard is different; it may be necessary to research the best wall construction techniques. A builder should be sure to pay special attention to proper drainage to avoid damage to the wall and surrounding areas.