Gravity Retaining Wall Construction
For AB, AB Aztec, AB Metro & AB Europa Retaining Wall Collection
Step 1: Site Prep and Excavation
If you are building with AB Fieldstone that uses recycled materials, go to AB Fieldstone installation.
- Remove surface vegetation and organic soils.
- Per the approved plan, excavate base trench a minimum of 24 in (610 mm) wide and 12 in (300 mm) deep.*
- Remove unsuitable soils and replace with compactible materials.
- Buried block should be a minimum of 6 in (150 mm). Check plans to see how much buried block is required.
- Compact and level trench.
- Walls built on a sloping grade require a stepped base.


- Begin excavation at the lowest point and dig a level trench into the slope until it is deep enough to accommodate the base material and one entire block.
- At this point step up the height of one block, and begin a new section of base trench.
- Continue to step up as needed to top of slope.
- Always bury at least one full unit at each step.
Step 2: Install Base Material
- Per the approved plans, place a minimum of 6 in (150 mm) of wall rock in the base trench and rake smooth.*
- Compact and level base material.
- Site Soils Engineer should verify that a proper base is established.
Step 3: Install Base Course
- Begin at the lowest wall elevation. Place all units top side up with the raised front lip facing up and in the center of the base material. Check and adjust for level and alignment of each unit.
- Drain pipe is required for walls over 4 ft (1.2 m) tall or are constructed in silty or clay soils. See approved plans for location and specifications.
Step 4: Install Wall Rock and Backfill Materials
- Fill the hollow cores and a minimum of 12 in (300 mm) behind the wall with wall rock.
- Use approved soils to backfill behind the wall rock and in front of the base course.
- Use a plate compactor to consolidate the area behind the block. Compact in lifts of 8 in (200 mm) or less.

Install base material, level and compact.

Level blocks, adjust where needed.
Step 5: Install Additional Courses
- Remove all excess material from the top surface of AB units. This can be done when installing the next course of block, by sliding the block into place.
- Stack the next course of blocks so that the vertical seams are offset from the blocks below by at least 3 in (75 mm) or 1/4 the length of the block.
- Check and adjust for level, alignment and the wall batter as the wall stacks up.
- Fill the block cores and behind the block with wall rock a minimum of 12 in (300 mm). Use approved soils to backfill behind the wall rock.
- From course 2 and above use a plate compactor to compact directly on the blocks as well as the area behind the blocks. Compact in lifts of 8 in (200 mm) or less.
- Complete wall to required height. See page 52 for information on wall ending options.
- Use 8 - 12 in (200 - 300 mm) of low permeable fill on the last lift to finish off wall.
*For walls under 4 ft (1.2 m), an 18 in (460 mm) wide by 10 in (250 mm) deep trench with 4 in (100 mm) of wall rock base material is acceptable.