In Los Angeles County, a significant proportion of the most expensive homes are on parcels of land that are past the angle of repose where slippage and erosion are a major concern. The reasons for this trend are two-fold. The scarcity of land has driven developers to use property that would not have been considered for home construction only decades ago. The other reason is that attitudes about the appropriateness of settled areas have changed radically. Today, many people want to be secluded from their neighbors. They also want the benefit of long vistas afforded by hilltop sanctuaries. Retaining wall technology has not only made this a practical reality, but it has made it an attractive alternative to life in the valley.

The Shape of Things to Come

Stackable systems like those manufactured by Pyzique, Versa-Lok, Unilock and Keystone, are designed for easy installation and versatility. What's more, they don't require mortar because gravity and pressure is enough to maintain their structural integrity. The combination of strength and design capability make these units particularly appealing for Landscape Architects who are looking to expand the range of their services by creating artistic views in geologically challenged landscapes.

Grade the soil backfill so water will run away from the wall face and direct runoff from adjacent areas away from the project site.

Staying the Course

The most common block wall systems are designed so that each course of stone is set back from the one below it 5/8 to 3/4 of an inch causing the walls to cant back into the retained soil at angles of approximately seven degrees. These canted or (battered) walls are structurally more stable than vertical walls because they have less horizontal force acting on the wall and gravity helps pull the walls back into the retained soil. They add layers and levels to the land and provide a unique aesthetic to any residential or commercial project.

Proper compaction of foundation and backfill soil is critical to long term performance. Loose backfill will add pressure on walls, collect water, cause settlement, and will not anchor soil reinforcement materials properly.

Tiers for Shears

When tiered retaining walls are used to break up the monolithic appearance of a large wall, precautions should be taken to ensure that the upper tier does not surcharge the lower wall. (To offset the effects of surcharges, move the wall away from the load or simply design the geosynthetic soil reinforcement to handle the loads.) Geosynthetics and soil combine to create reinforced soil structures that are strong and massive enough to resist forces exerted on them.

Soil reinforcement type, length, and vertical spacing will vary for each project and should be specified by a qualified engineer. However, as a general rule, never overlap soil reinforcement layers directly on top of each other. Slick surfaces of geosynthetics will not hold in place properly when put directly on top of one another.

In addition to enhancing the structural integrity of the property, curved and tiered retaining walls can create unique layers of vegetation subdivided by arcs of stone.