More so than other landscape structures, retaining wall construction exemplifies the design principle that form follows function. The size of a wall and material choice should be determined by the grade of the immediate terrain as much as aesthetics. Water runoff from surrounding buildings and lots also have an impact on design and construction. Retaining wall construction and design can expand usable garden space by terracing, or just make a property more useful by providing access to a lower level entrance such as a walkout basement or sunken garage. Dry stack natural stone or engineered block is usually the most cost effective method but mortared masonry and even poured concrete are also options. Visually, both retaining walls and free standing walls as well as garden accent walls can serve as the foundation of a garden design offering some visual structure to the landscape and even some off-season interest when plants are dormant.
In cases where a level space is not required but soil erosion is still a concern, trees and plants can be used in combination with stone slabs or outcroppings to help manage water runoff. This approach can become a very effective erosion control at considerably less cost than a complete retaining wall. With this approach the issue of hydro static pressure behind a wall is completely avoided which is a common cause of wall failures. Large stone slabs installed into a hill add visual interest as well as some immediate erosion control giving the plants time to grow and spread creating their own soil retention system.
Older, neglected retaining walls can often be repaired or rebuilt. Even with a complete failure existing materials can almost always be salvaged and reused. The increasing cost of natural stone is making this approach even more cost effective. This is easiest with dry stack stone or block walls with no mortar to remove and replace. As with new construction, controlling and directing water runoff is always addressed to insure against future problems, following sealed drawings by an Ohio registered engineer when needed.