Surface vegetation must be removed from the area and cannot be use as backfill material. Starting at the lowest point, dig a base trench the length of the wall. Base trench for a Gravity Wall is at least 18 in. wide by 7 in. deep (457 mm by 178 mm). The base trench for a Reinforced Wall is wider and deeper to handle the load. A minimum of 24 in. wide by 12 in. (610 mm by 305 mm) deep is recommended.

Place, level, and compact a layer of 0.25 in. to 0.75 in. (6.4 mm to 19.1 mm) base rock to support the first course of block. Average amounts are 4 in. deep (102 mm) for Gravity Walls and 6 in. (152 mm) for Reinforced Walls. Check the entire length for level and adjust as needed.

If you are building into a hillside, continue to excavate into the slope creating step-ups until you have reached the top.

Starting at the lowest point of elevation, place the blocks on top of the compacted base, with the raised front lip facing up and forward. Place the blocks closely together, checking the level and alignment of each block. A small amount of coarse sand could help in setting the base course.

Using a rubber mallet, modify where necessary to ensure a straight and level base course.

Fill the hollow cores and 6-to-8 inches (152 mm to 203 mm) behind the blocks with clean stone. This creates the drain field. Use on-site soil to fill the area behind the drain field and to fill any gaps in front of the base blocks. Use a plate compactor or hand tamper to compact the wall, drain field and area directly behind the drain field.

Compact parallel with the wall, with the first pass directly over the top of the blocks. Continue to compact until the soil no longer settles. Check for level, and adjust where necessary. Remove all debris from the top of the blocks to prepare for the next course. A push broom works good for this.

If the wall requires reinforcement, go to Step 5. If not, continue installing additional courses in the same manner until the desired height is acquired.

TIP: For your base and drain field, use crushed stone varying in size from 0.25 in. to 0.75 in. (6.4mm to 19.1mm). This will compact well and still allow for good drainage. For the backfill soils, avoid using soft, wet clays or spongy, organic soils. These soils will not compact well, and continue to settle after construction.

Install the next row of blocks with an offset (stagger) of at least 3 in. (76 mm) from the course below. The vertical seams of the blocks should be staggered and not directly line up. Check again for level and alignment, adjusting where necessary.

Once again, fill the hollow cores and drain field with clean stone, using on-site soil to fill behind the drain field. Compact the wall and the drain field as before, with the first pass directly over the top of the blocks. Check for level and alignment adjusting where necessary.

Soil reinforcement increases the strength of the wall by creating a reinforced mass of soil behind the blocks. The weight of the reinforced soil mass combines with the block for a heavier, stronger wall.

After determining the number of layers needed, you'll then need to determine the number of rolls required. To do so, multiply the length of the wall by the number of layers needed, then divide by 50 (the length of one roll of grid).

A typical wall is reinforced every two courses. This process should be started just after the first row of blocks has been installed, filled, compacted, and adjusted for level.

Roll out the reinforcement grid behind the wall with the edge of the reinforcement grid against the lip of the block.

When placing grid along curving walls, the grid should always follow the back of the lip. To accommodate the curves, simply slit the grid with a utility knife, and either overlap it for outside curves, or feather it out to follow inside curves. When placing grid at corners, simply lay grid into the corner and cut it to fit with a utility knife.

Place the next course of block on top of the reinforcement grid. Pull on the back of the reinforcement grid to remove any slack and stake the reinforcement grid in place. Fill the hollow cores and drain field with drainage rock, and use on-site soil to fill behind the drain field as before. Compact the wall and the drain field, with the first pass directly over the top of the blocks. Check for level and alignment, adjusting where necessary.

Stack and backfill another two courses of block. Compact thoroughly, and rollout the next layer of grid.

CAUTION: Do NOT compact directly over reinforcement grid or drive heavy machinery WITHIN 3 ft. (O.9 m) of your wall. Heavy machinery may cause your wall to rotate forward out of alignment.