Pattern Wall Construction

Step 1: Excavate and Install Base Course

Refer to the gravity wall instructions for a detailed description on how to install the base course. Basic steps include: site prep and excavation, installing base material, base course, wall rock, backfill materials, geogrid - if necessary and compacting.

Note: Full-sized blocks should always be used for the base course with a Standard Pattern, and for Lite Patterns, half width blocks. This will speed the leveling and installation of the first course.

Video: Build a Reinforced Patterned Retaining Wall with Geogrid

Step 2: Install Geogrid

Refer to the plans for placement of grid; this example requires grid on top of the base course.

• Remove all excess material and slag from the top surface of the base course. This prepares a smooth surface for placement of the geogrid and the next course of blocks.
• Cut sections of geogrid to specified lengths. Check manufacturer’s grid specifications for strength and roll or machine direction. Refer to the approved plans for exact size and location.
• Install the layer of geogrid by placing the cut edge up to the back of the raised front lip and roll the layer out to the back of the excavation area to the length specified in the approved plans.
• For retaining walls that require geogrid reinforcement, selection of which pattern to use is determined by the grid spacing shown on the approved plans. If grid is required every 2 courses, then use a 2 course pattern; if 3 course grid spacing is required, use a 3 course pattern.
• If building with a random pattern, the pattern must be leveled off at the appropriate courses to allow for the installation of geogrid on a flat surface.

Step 3: Install The Multiple-Course Pattern

The retaining wall example shown here uses a two (2) course pattern. Check the approved plans to determine the best pattern option for the project

• Stack the first course of the pattern on top of the geogrid and the base course.
• Check blocks for level, and make adjustments as needed. Pull on the back of the geogrid to remove any slack. If necessary, stake in place.
• Install the wall rock in the block cores and 12 in. (300 mm) behind the blocks to the height of the blocks. Compact inside the block cores using a shovel handle. Check blocks for level.
• Install the wall rock in the block cores and 12 in. (300 mm) behind the blocks to the height of the blocks.
• Compact inside the block cores using a shovel handle. Check blocks for level. Learn more about compaction in the block cores.
• Use infill or approved on-site soils to backfill behind the wall rock in the reinforced zone. The height of the wall rock and backfill material cannot exceed 8 in. (200 mm) before compacting. The top of the blocks will not always match up with each lift of soil.
• Using a mechanical plate compactor, compact the wall rock and infill materials behind the block in maximum 8 in. (200 mm) lifts. Compact directly behind the blocks in a path parallel to the wall, working from the back of the wall to the back of the excavated area. Compact to a minimum of 95% Standard Proctor.
• Check blocks for level. and then install the remainder of the 2 course pattern. Install wall rock in the block cores and behind the blocks as before. Use approved infill soils to backfill behind wall rock. Check blocks for level and for batter.
• With the first multiple-course pattern completed, use a plate compactor to compact the wall rock in the block cores and the wall rock behind the blocks. The first pass of the plate compactor should be directly over the top of the block cores.
• After running the plate compactor on top of the blocks and wall rock, compact the infill material immediately behind the wall. Compact in a path parallel to the wall, working from the front of the wall to the back of the infill material. Compact to a minimum of 95% Standard Proctor.
• Check and adjust for level and alignment and wall batter as the wall stacks up. It is acceptable to shim under blocks to compensate for a build up of tolerances or an out of level base condition. Asphalt shingles or geogrid work well when shims are required. The maximum allowable shim thickness per course is 1/8 in. (3 mm).
• Keep all heavy equipment at least 3 ft. (0.9 m) away from the back of the wall.

Step 4: Install The Second Multiple-Course Pattern

The retaining wall example shown here uses a two (2) course pattern. Check the approved plans to determine the best pattern option for the project

• Refer to your approved plans to determine if reinforcement will be required. If so, repeat the previous process to install geogrid between the patterns.
• Install the next pattern section as done in the previous steps. Each additional pattern will need to be offset from the pattern below to avoid a repetitive look. Remember to offset the vertical seams by at least 1/4 of the block whenever possible.
• Two course patterns should be selected for most projects. Three course patterns can be used for gravity walls or to top off a reinforced wall where geogrid is not required within the top three courses.

Step 5: Ending and Topping off Wall

Patterned walls may be ended with a step-down or a turn-in. When ending a patterned wall, discontinue the pattern and randomly adjust as necessary to meet the site conditions.

• Finishing a patterned wall is the same as finishing a standard retaining wall. The only requirement is that a multiple course pattern must be completed so that the top course of blocks forms a level surface.
• Use 8 in. (200 mm) of impermeable fill on the last lift to finish off wall.

Install base course with full size units and compact

Install geogrid

Stack first course of pattern and backfill wall rock in block cores

Compact wall rock and backfill materials parallel to the retaining wall

Compact on blocks first and then the wall rock and backfill materials when the pattern is completed

Install geogrid and offset additional patterns to randomize the look

Compaction on Patterned Walls

Compaction in the block cores needs to be done regularly when working with patterned walls. This can be done by using the end of a shovel to compact the wall rock, adding additional rock if necessary.

At each 8 in (200 mm) lift, compact the block cores with the end of a shovel, and the area directly behind the block with a plate compactor per the procedures described in this manual.

At the conclusion of each pattern, the top of the wall will be level. Run the plate compactor over the top of the blocks to consolidate the wall rock. Place grid if required, and begin the next pattern.