Gravity Wall Construction using AB Fieldstone

For complete details on the proper steps for site prep, drainage requirements and installing the base material, see AB Gravity Walls Installation Steps 1 and 2. Most designs will require a local wall design engineer or a site civil engineer to develop approved plans. The projects must be built to these approved plans and specifications.

Step 1: Base Course for AB Fieldstone

• Begin at the lowest wall elevation by placing the AB Fieldstone facing units on the base material towards the front of the trench, leaving room for the AB Fieldstone anchoring unit so when entire assembly is installed it is centered on the base materials. Check each unit and adjust for level and alignment. The facing units can be randomly flipped upside down to give different facing appearances.
• For proper placement of the anchoring units, use a brick hammer or shovel to create a small trench to allow for the lip.
• Install the anchoring units into the receiving slots of the facing units with the lip facing down in the trench just created. Make adjustments to ensure anchoring units are installed reasonably level with the facing unit. The anchoring units should never be installed higher than the facing unit. Except for special applications like corners, each anchoring unit should match up with one facing unit.
• A drain pipe is required for any reinforced wall, gravity walls over 4 ft. (1.2 m) tall or sites with poor drainage. Place the drain pipe at the lowest possible point toward the back of the trench and vent to daylight every 50 ft. (15 m). See approved plans for location and specifications. Learn more about water management.

Step 2: Install Wall Rock and Backfill Materials

• Fill the hollow cores and a minimum of 12 in. (300 mm) behind the wall with wall rock. Install the wall rock to be level or below the receiving notch of the anchoring unit.
• 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 blocks.
• Compact in lifts of 8 in. (200 mm) or less

Backfill with wall rock.

Step 3: Additional Courses for AB Fieldstone

• Remove all excess material from the top surface of the AB Fieldstone units. This should include running a brush or broom across the receiving notch to remove any debris.
• For faster installation and alignment of the second course, install the first AB Fieldstone facing unit and AB Fieldstone anchoring unit at the same time. Make adjustments so that the vertical seams are offset from the blocks below by at least 3 in. (75 mm) or ¼ the length of block.
• Install the rest of the facing units using the first block as a placement guide.
• Place anchoring units into the receiving slots of the facing units. Slide the two piece assembly so that the lip of the anchoring unit is placed into the receiving notch of the block on the course below. Each anchoring unit should match up with one facing unit.
• Check and adjust for level and alignment of the facing units.
• Fill the hollow cores and a minimum of 12 in. (300 mm) behind the wall with wall rock. Install the wall rock behind the anchoring unit to be level or below the receiving notch or approximately 0.5 in. (12 mm) below the top of the anchoring unit.
• 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.
• Remove excess material from the top surface and repeat steps to complete the wall to the height required. More for information on ending walls with turn-ins.

When Stepping up the Wall Base is Needed

When building Step-Ups into a slope, always begin at the lowest wall elevation of the base course.

To create a Step-Up, span a block between the leveling pad and the block course below. Step-Ups are most stable when the upper block has sufficient bearing on the lower block. The length of the 824 assembly (if available) provides the flexibility to make this block ideal for this application. An 812 assembly will work as well.

AB Fieldstone is a multi-piece retaining wall system where each block assembly consists of a facing unit and an anchoring unit. These universal anchoring units, short anchoring unit (SAU) and long anchoring unit (LAU), are made of recycled materials and are used with the 812 and 824 facing units. The long anchoring unit is an option for job sites that require taller walls, but do not have room for excavation and geogrid placement.

• The maximum gravity wall heights using short anchoring units, with either of the two facing units, is up to 5 ft 8 in (1.7 m) in good soil conditions.
• The maximum gravity wall heights using long anchoring units, with either of the two facing units, is up to 9 ft 8 in (3.0 m) in good soil conditions.

Good soils conditions are defined as well-graded compactible granular aggregate, with an internal angle of friction of 36° or greater. You should always consult a registered professional engineer to determine actual site specific requirements or to account for seismic loading. See complete Maximum Gravity Wall Height Chart.

812 facing unit with short anchoring unit (SAU).

824 facing unit with short anchoring unit (SAU).

Long anchoring Unit.
(use with 812 or 824 facing units)