Successful installation begins with proper planning: the site soils, groundwater, horizontal and vertical layout, structural design, wall loadings, observation, testing and construction assurance are all vital to building a quality wall. If your wall is taller than four feet, or has a steep slope at the top of the wall, in front of the wall, or a load will be on top of the wall (parking spot-driveway etc), consult an engineer before starting your project planning and construction.

1. Lay Out the Wall

Select the wall location and length for the retaining wall and, using wooden stakes and a string line, plan out the wall. If necessary, have a qualified professional surveyor stake out the wall according to the lines and dimensions on the stamped engineering plans. Verify the proper locations with the project superintendent or homeowner.

2. Excavation

Verify that the layout dimensions are correct and excavate to the lines and grades as shown on the stamped and approved construction plans. Install erosion and sediment control measures according to plan. If possible, perform excavation during dry weather to reduce erosion and sediment issues. Remove all vegetation and organics, and other debris. Check that the foundation sub-grade is suitable. If any conditions exist that are unacceptable, do not proceed until they have been corrected. Proceed excavating the leveling pad to obtain proper block embedment. For small Valley Stone gravity walls, the minimum embedment is 150 mm (6 inches). Prior to excavating or digging any trenches, call before your dig. Calling 811 is a free service that will notify all agencies to mark their underground utilities. Allow 48 hours prior to beginning construction. This will prevent any possible disruption in service to your neighbors, damage to your equipment, or possible serious injury or death to you, should you contact a high power line. Sloping Toe: the minimum embedment in front of the wall will increase when there is a slope in front of the wall. Most municipalities follow the British Columbia Building Code and/or municipal requirements, which establishes rules and regulations. The minimum horizontal bench in front of most walls is 1 m (4 feet), however, you should check with your local building department as regulations varies per municipality.

3. Leveling Pad

Start the leveling pad at the lowest elevation along the wall and work upward, always maintaining a fully buried block. The leveling pad’s minimum width is the unit width plus 300 mm (12 inches); the minimum leveling pad’s depth is 150 mm (6 inches) plus the height of the block. The leveling pad shall consist of 6 inches of a well-compacted (95% Standard Proctor) angular material (12 mm {1/2 inch} road base or 19 mm {3/4 inch} clean crushed angular rocks). The wall must step up in equal increments, always maintaining unit embedment, (see page 10, figure 4.1). Pea Gravel, sand or other material that is round or organic in nature is not acceptable for use in a leveling pad.

4. Base Course

Place the first course of Valley Stone units side by side, with each block touching the next; do not leave gaps or spaces. Each block should be leveled front to back and side to side. When consecutive blocks are laid, check the level of multiple blocks using a four-foot level. Ensure that the units are in full contact with the base. Place a string line at the back of the blocks to ensure your wall is straight and true to the intended lines. (see figure A)

5. Pins

Valley Stone units have two setback options; front pin position (near vertical position), and the rear pin position (25 mm or 1 inch setback). Also available is an optional 12 mm (1/2 inch) position, which is a combination of alternating the front and rear position. (see figure B)

6. Drainage Pipe

Install a minimum 100 mm (4-inch) diameter perforated or slotted PVC pipe behind the blocks. Outlet the drain pipe to a storm drain, or daylight the pipe where the water will flow away from the wall face. On walls longer than 30 m (100 feet) (see page 13 - 4.5 Drain Pipes) you will need to daylight the drain pipe through the front face of the wall every 15 m (50 feet) and at each end connecting to a storm drain, so that the water drains away from the wall. (see figure C)

7. Backfill and Compaction

After installing the pins and the drain pipe, place 19 mm (3/4 inch) clean crushed angular rock 600 mm (24 inches) behind the face of the block, filling all voids and cavities in the Valley Stone block and covering the drain pipe. Place the wall backfill material behind the drainage rock in maximum of 203 mm (8 inch) lifts or to a height that your vibratory equipment is capable of compacting. Compact the soils to 95% Standard Proctor Density using the appropriate compaction equipment. When compacting within 900 mm (3 feet) of the back of the wall, use only hand operated equipment.

8. Installing Additional Courses

Prior to laying the next course, sweep the bottom course free of rock or other debris. Place the block so that the unit is centered above where the two bottom units meet. This is called a “Running Bond” pattern. Place the block so that the pins fit into the pin receiving holes, pulling the units toward the front of the wall. Once placed, check the blocks to ensure that they are level and in the correct batter. Periodically, you may need to “shim” the blocks. Use the correct material including, but not limited to, asphalt roofing material, geogrid, or polyester rope. After the next course has been placed, continue with placing the pins in the pin receiving holes and with backfilling the blocks, placing 19 mm (3/4 inch) clean crushed angular rock from the face of the block, back 600 mm (24 inches). Place the structural backfill material in lifts no greater than 203 mm (8 inches), or according to the capabilities of your equipment. When you have completed backfilling and compacting, sweep the blocks and start your next course, or if you have reached your desired height, follow the “Capping the Wall” steps. (see figure D)

9. Installing Geogrid

Geosynthetic reinforcement is required for taller walls or walls constructed in poor soils, or where the wall is supporting critical structures. Prior to installing geogrid, you should consult a qualified professional engineer and obtain the approved set of construction plans. The first step when installing geogrid is to install the pins and sweep the blocks of any debris. Measure and cut the geogrid according to the approved plans, then install the geogrid reinforcement, ensuring that the strength direction is laid perpendicular to the wall. Stack the next course of blocks to secure the geogrid reinforcement in place, then pull the geogrid reinforcement taut, eliminating any wrinkles or slack. After the geogrid and block course have been placed, continue with placing the pins in the pin receiving holes. Backfill blocks. Place 19 mm (3/4 inch) clean crushed angular rock from the face of the block back 600 mm (24 inches), then place the structural backfill material. (see page 9, 3.2 Geogrid Reinforcement). (see figure E)

10. Capping the Wall

When the design heights are achieved, start to cap the wall with the appropriate Valley Stone capping unit. Start by first sweeping the retaining wall blocks so they are free of rocks and debris. Place the caps from the lowest point and work toward the top. Use a masonry concrete adhesive to secure the caps in place. The caps can be installed with an overhang, also known as a shadow effect, or they can be placed flush with the retaining wall block. (see figure F)

11. Final Grade

The final grading or planting can now be put in place. This final lift is typically an 203 mm (8 inch) layer of low permeability soil. This is to help prevent water from penetrating into the reinforced soil zone and creating potential problems. Do not make any changes to this area without the approval of the design engineer.