Retaining Wall Styles
Armour Stone or boulder stone retaining walls are built using natural stones. Amour stones are removed from quarries, and boulder stones are the product of site development excavations. These stones retain the soil behind them by their weight. Each stone will weigh anywhere from 500 to 3000 pounds. These retaining walls are generally laid without the need for mortar or glue because the weight of the stones and stone-to-stone friction from the contact between stones creates enough shear strength to retain the soil.
Pre-cast Wall Blocks are manufactured in a controlled environment and are specifically designed for retaining walls. They have construction specs appropriate for the exact retaining wall stone being installed. These wall stones often have notches or keys to help increase the load-bearing ability of the overall retaining wall. The height and load-bearing requirements of the wall will determine the appropriate size of each pre-cast wall stone unit.
Concrete Block retaining walls are pre-cast hollow units designed to be stacked vertically, mortared in place, and filled with stone or concrete. These retaining walls are usually faced with a veneer stone or brick for an esthetic appeal. The construction of these walls has more steps involved and therefore can cost more than pre-cast retaining wall stones.
For a more functional landscape area, retaining walls can be used to flatten a sloped or steep hill to create more usable room in your yard. In addition, they can be used for erosion control and soil stabilization, helping with drainage issues, making elevation changes, and border steps. A good landscape design can take a very unusable space and incorporate retaining walls to create different areas within the yard utilizing elevation changes. Layered gardens or tiered lawns, sunken rooms, and walkout basements are all examples of spaces that will use retaining walls to create usable spaces.
Retaining Wall Costs
Different factors will determine the costs of a retaining wall. For example, assessment of appropriate materials to be used, the structural requirements, existing soil and drainage issues, and site access will all play into the overall cost of the retaining wall.
Does the Wall Need a Permit or Engineered Drawing?
If your wall is greater than 1 meter in height, it will need an engineered drawing. Check with your local municipality to determine whether a permit and engineered drawing are required. Ariss Landscape Inc. will handle these tasks upon agreement of a quote.
How Long Will a Retaining Wall Last?
A properly constructed retaining wall should last 80-100 years. If the wall fails before this, one or more construction elements were not completed correctly.
Two different retaining walls are used in residential sites; Gravity Walls and Soil Stabilized Walls. These two use similar elements. The soil stabilized wall will also incorporate a soil reinforced zone using geogrid to add extra stabilization. Proper construction of retaining walls will follow these steps:
- Excavation of the area a minimum of 12 inches depth below the finished grade and 22 inches of base width
- Proper assessment of the sub-grade to determine if amendments are needed
- Geotextile fabric installed above the compacted sub-grade
- A minimum 6-inch foundation base is installed in either a dense-graded or open-graded form, compacted to the appropriate density
- A bedding layer is laid above the base to smooth out any minor imperfections in the base.
Wall Course & Drainage
- The first course of wall stone is laid perfectly level to ensure the subsequent layers are level
- A drain tile is placed according to the construction drawings height, enclosed in clear drainage aggregate
- The following layers of wall stones are laid according to the pre-determined size of the wall.
- Backfill of drainage stone is placed as each course is applied and is wrapped in geotextile fabric
- For Soil Reinforced Walls, geogrid is laid between courses and extended a minimum of 4 feet from the wall
- The wall is topped with glued wall caps
- A layer of low permeability material is laid above the drainage stone and compacted
- The final grade material is laid