Step 1
Surface vegetation must be removed from the area and cannot be used 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.
Base trench for a Reinforced Wall is wider and deeper to bear the load. A minimum of 24 in. wide by 12in. deep is recommended.
Average amounts are 4 inches deep for Gravity Walls and 6 inches 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.

Step 2
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.

Step 3
Fill the hollow cores and 6-8 inches behind the blocks with drainage rock; this creates the drain field.
Use on-site soil to fill the area behind the drain field and to fill in any gaps in front of the blocks.
Using a plate compactor or hand tamper, compact the wall, the drain field and the 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.

Step 4
Install the next row of blocks with an offset (stagger) of at least 3 inches from the course below. The blocks’ vertical seams should not directly line up.
Check again for level and alignment, adjusting where necessary by using shims.
Once again, fill the hollow cores and drain field with drainage rock, 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.
If the wall requires reinforcement, continue on with the next step. If not, continue installing additional courses in the same manner until the desired height is acquired. Then, skip to the last step for finishing options.

Step 5
A typical wall is reinforced every to 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 geogrid behind the wall with the edge of the geogrid against the lip of the block.
Place the next course on top of the geogrid and offset from the previous course below.
Pull on the back of the geogrid to remove any slack. Stake the geogrid in place.
Fill the hollow cores and drain field with drainage rock, using on-site soil to fill behind the drain field as before.
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.
DO NOT compact directly over geogrid or use any heavy equipment WITHIN 3 feet of your wall. Heavy equipment may cause your wall to rotate forward out of alignment.

Step 6
Using one of the following methods, natural or capped, will give your wall a flawless, finished look.
The raised front-lip provides a perfect built-in edging to complete your project. Simply use rock, mulch, grass or planting soil to create an attractive, natural look.
For a professional look, Allan Block capstones are available to finish the top of the wall. These should be placed along the wall and fixed in place with a high-grade, waterproof construction adhesive.

Tips
Your entire installation will go more quickly with a level base.
Expecting rain? Keep a roll of plastic on hand to cover your base trench.
Using a string line helps keep the blocks in alignment.
A 4-6lb “dead blow” hammer is a great help when setting the base course.
Coarse sand, Asphalt shingles or geogrid fabric work well for shims

HAND TOOLS – Safety glasses, gloves, dust mask, ear protection, knee pads, 4’ level, torpedo level, tape measure, string line, chisel, hand tamper, rubber mallet, shims, broom, round and square shovel.

POWER TOOLS (Optional) – Concrete saw with diamond blade, plate compactor, bobcat, transit/site level.