Building a Reinforced Retaining Wall
Install geogrid on
every other course as needed.
What is Geogrid?
Geogrids are flexible, synthetic meshes which are manufactured specifically for slope stabilization and earth retention. These “grids” are available in a variety of materials, sizes and strengths. They can be made of high tensile strength plastics or woven polyester yarns and are typically packaged at the factory in rolls.
Use the Soil Reinforcement Chart to determine the size of AB Grid you will need and how many layers your retaining wall requires.
How Grid Works
The sand castle test takes two cylinders of soil and applies vertical force to see how the soil performs. The first cylinder is just compacted material. The second is also compacted material with the addition of mesh screens to simulate the use of geogrid reinforcement. Learn more about how grid works...
See the importance of reinforcement in your retaining
wall with this sand castle demonstration.
For AB, AB Aztec, AB Metropolitan & AB Europa Walls
Install Reinforcement
If you are building with AB Fieldstone that uses recycled materials, go to Fieldstone installation
- Once the base course is complete, begin installing the first layer of AB Reinforcement Grid. When using AB, AB Aztec, AB Metropolitan or the AB Europa Collection, begin by placing the edge of the geogrid against the back of the raised front lip and rolling it out along the retaining wall. For AB Fieldstone, place the edge of the geogrid in the middle of the facing unit. Always refer to your approved plans for exact size and location.
- Stack the next course of blocks so that the vertical seams are offset from the blocks below by at least 1/4 the length of the block.
- Sight down the retaining wall line to check for alignment. Blocks may be adjusted slightly to form straight lines or smooth flowing curves.
- Pull on the back of the geogrid to remove any slack. If necessary, stake it in place. Never drive or compact directly on the geogrid. This will cause damage to the geogrid.
Never compact directly on top of grid.
Backfilling and Compaction
- Install wall rock in the block cores and 12 in. (300 mm) behind the block. Use infill or approved on-site soils to backfill behind the wall rock to the height of the block.
- The wall rock and infill soils behind the retaining wall must be properly compacted using a plate compactor. Compact in lifts of 8 in. (200 mm) or less, this time starting on the block and working in a path that runs parallel to the block and towards the back of the excavated area. Always make a minimum of two passes with a plate compactor. Compaction should be continued to achieve solid, movement-free soil.
- Remove all excess material from the top surface of all blocks. This prepares a clean, smooth surface for placement of the next course.
Additional Courses
- Continue installing your next courses of block using the steps shown above. Per your approved plans, install geogrid on every other course of the retaining wall.
- Using these steps complete the retaining wall to the desired height. On the last course, fill behind the blocks with organic soils in place of infill or approved on-site soils. This will assist in any plantings above the retaining wall and also to direct water from running behind the blocks. More information on finishing your retaining wall.
Install AB Reinforcement geogrid
Install next course
Backfill and compact
Install next course of block and layer of geogrid
Reinforcement Chart
Match your wall to the conditions below to find which width and the number of layers of AB Reinforcement Geogrid you will need. To determine the number of rolls needed, multiply the length of your wall (in feet) by the number of layers needed, and then divide by 50 (the length of a roll of AB Reinforcement Geogrid). Typically most soils will be considered clay, for sandy conditions outlined in the table the soil must be a clean, granular material. Not sure what soil type you have?
For walls taller than 6 ft (1.8 m) or commercial applications, see our AB Commercial Retaining Wall Manual.
Large Geogrid Rolls
Large roll geogrids are strongest along the roll or machine direction and are cut to the design length. They are best suited for retaining walls over 6 ft. (1.8 m) high.
AB Reinforcement Grid™
AB Reinforcement Grid is biaxial which means it has the same strength in both directions and can be simply rolled out along the wall. It is available in 3 ft. and 4 ft. rolls and is 50 ft. long (0.9 m and 1.2 m by 15 m) and is best used for residential retaining walls under 6 ft. (1.8 m) tall as outlined in the table above.
When placing geogrid along curving walls, the geogrid should follow the back of the lip. Simply slit the geogrid with a utility knife and either feather out or overlap to follow the curve.
When placing geogrid at corners, simply lay the geogrid into the corner and cut to fit with a utility knife.
