Retaining Walls Over 8 Feet High

Retaining Wall Construction

• The weight of soil retained by a wall exerts lateral pressure on the wall. A surcharge is added when a vertical load imposes more weight on the retained soil, such as footings from a structure, a slope, traffic loads or a fence. Retaining wall failure has serious consequences, especially if it's located in a high-use area. Construction techniques focus on prevention of sliding, overturning, or foundation failure. Experienced designers will balance the factors of cost and construction for the final plan.

Retaining Wall Types

• Gravity walls are the simplest walls to construct. They use the weight of the material and a batter, or angle, back into the soil for strength and to resist overturning and sliding from lateral pressure. Cantilever walls bury a footing below grade, placing the wall -- called the stem wall -- on top of the footing. The wall is uniform thickness. Counterfort walls add triangular supports on the soil side of the wall for added strength to the cantilever design.

Cantilever or Counterfort Walls

• Gravity walls are recommended for heights up to 10 feet, but in practice it's more common to employ the cantilever or counterfort design for walls higher than 4 feet. They make more economical use of material to achieve the design objective. Often retaining walls are built to create more usable space for construction such as roads and buildings. It's essential that the wall maintain structural integrity, especially if there's development on the high and low sides of the wall.

Living Retaining Walls

• Bioengineered retaining walls are becoming part of the urban landscape, for improved aesthetics and to use plants for slope retention and erosion control. The walls use retaining structures, such as pre-cast concrete units, combined with a soil mix and plants as part of the structural design to stabilize the slope. Walls that are 8 feet or higher allow deep soil and substantial planting. Most of the wall construction is designed to disappear visually as the plants grow.