Dig a trench for the bottom row of blocks. They should be buried about 1 inch deep for every 8 inches of wall height. This provides strength and stability to your retaining wall. Make sure that your trench is level and compacted.
Excavate a shallow trench at the base of your planned wall. It should be a minimum of 24" wide and 8" deep to accommodate the leveling pad material and required unit embedment below grade. Place a minimum of 6" of base material in the leveling pad layer.
The depth of retaining wall and breast wall below ground level or terrace level shall be at least 500 mm below side drain within soil or highly jointed rock and foundation shall be on natural firm ground.
Each hole is to be dug to the recommended depth (dependant on the wall height – rule of thumb half in the ground half out ie. 600mm high wall will require 600mm of post to be cemented into the ground) * Add 100mm to the depth of each hole for 20mm drainage gravel.
Retaining walls are functional features that keep soil in place and turn sloped land into flat, usable space. Typically, your retaining wall should be between 3 to 4 feet tall to serve its purpose without requiring structural support and intricate engineering.
Base thickness = 1/8 of the height of the wall but not less than 12 inches. Stem thickness = 6 inches + ¼ inch for each foot of wall height.
Dig a trench for the bottom row of blocks. They should be buried about 1 inch deep for every 8 inches of wall height. This provides strength and stability to your retaining wall. Make sure that your trench is level and compacted.
A commonly used embedment depth calculation for walls with level ground below is 1 in (2.5 cm) of depth per foot (30 cm) of wall height with a typical minimum of 6 in (15 cm) for commercial projects.
Fill trench with 1 1/2″ processed gravel or 3/4″ crusher run base material and firmly compact in 2-3″ layers until base is 6″ thick. Place and level the first course of wall units on the base. Place perforated pipe behind the wall for drainage and backfill with 3/4″ crushed stone.
Allan Block commercial/reinforced retaining walls will require at a minimum 12” for excavation (6” for gravel, 8” for buried block). The taller the retaining wall, or if there is a slope ABOVE or BELOW the wall, the more blocks need to be buried and the deeper the excavation will need to be.
The rule for retaining posts is generally half and half. If your retaining wall is 600mm you must dig a post hole of the same depth. However, the rule for fencing is 1/3 the height of the fence post. Therefore if the fence post height is 1400mm, the fence post hole must be at least 467mm.
The basic principle for the design of the Retaining Wall is that the reinforced concrete stem and footing flexure and shear design strength must e at least equal to the factored moment and shears determined from the analysis. The wall stem is designed as a cantilever, fixed at the footing.
In this case, you would need to excavate a base that is at least 2.5 feet deep to provide adequate stability for the wall. Understanding the importance of depth calculation is crucial when constructing a block retaining wall.
Absolutely! Even a 2-foot retaining wall needs an effective drainage system. Without it, water can build up behind the wall, leading to pressure that might cause the wall to lean or even collapse. All walls need systems to manage water effectively, preventing damage over time.
Medium Walls (4 to 10 feet):
The thickness can vary between 12 and 18 inches, contingent upon slope and soil characteristics.
Plan to backfill the wall with well-draining gravel or sand. Higher walls or areas with soil that stays wet may need a drainage pipe. Keep in mind that clay soil retains water and sandy soil drains too easily. You'll need a well-draining soil mix behind your landscape retaining walls.
The footing, or first row of your retaining wall, should be about 4 to 6 inches deep and about 12 inches wide, or twice the width of the block you are using. The blocks should sit about halfway into the soil.
Drainage and back fill
Place 100mm pvc agricultural pipe (with sock if required) behind the wall, with a 1 in 100 fall. Backfill behind the courses of blocks to a width of 200-300mm using 10-20mm clean aggregate. Ensure each block is filled with clean aggregate.
General Embedment Requirements
The general guideline is a minimum of 6 in. (150 mm) of buried block with 1 in. (25 mm) embedment per 1 ft.
In summary, retaining walls do need a footing to ensure they are structurally sound and have proper drainage to prevent cracking or collapse. Without a footing, the ground beneath the retaining wall can shift, which can cause the wall to shift as well, leading to cracking or collapse.
Concrete is a common material for retaining walls because of its strength and durability. The typical lifespan of these walls is between 40 and 100 years, although they can persist for several decades.