Retaining Walls - Allan Block
Installation
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Step 1 Base Preparation - View Animation video  Speed: LOW HIGH

Surface vegetation must be removed from the area and can not 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 (457mm by 178mm). Base trench for a
Reinforced Wall is wider and deeper to handle the load. A minimum
of 24 in. wide by 12 in. (610mm by 305mm) deep is recommended.

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

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

Step 2 Base Course - View Animation video  Speed: LOW HIGH

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 Backfill - View Animation video  Speed: LOW HIGH

Fill the hollow cores and 6-8 in. (152mm-203mm) 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 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 well for this.

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

Step 4 Additional Courses - View Animation video  Speed: LOW HIGH

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

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.

Step 5 Reinforcement - View Animation video  Speed: LOW HIGH

Lock your wall in place with Allan Block’s
Advanced Soil Reinforcement 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. Place 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.

Do NOT compact directly over reinforcement grid or drive heavy machinery
WITHIN 3 ft (0.9m) of your wall. Heavy machinery may cause your
wall to rotate forward out of alignment!

Step 6 Grid Installation Details for Curves and Corners

When placing grid along curving walls, the grid should follow the back
of the lip. Simply slit the grid with a utility knife and either feather
out or overlap to follow the curve.


When placing grid at corners, simply lay grid into the corner and
cut to fit with a utility knife.