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.
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.
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.
Do you need drainage behind a retaining wall? Yes, which means you need backfill too. This backfill is the soil that's located in the first 12 inches of space right behind the retaining wall in order to have proper drainage, and it can be either gravel or crushed stone.
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.
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.
Soil saturation is the most common external factor that causes retaining wall failure, but there are many ways to prevent it.
Concrete block retaining walls must be stronger than freestanding walls. Insert rebar in the footing when you pour it; this should be done every three blocks or at intervals specified by your local codes.
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.
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.
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.
In conclusion, deciding between a cinder block retaining wall and a concrete one is a matter of preference. Both materials have unique benefits and drawbacks that must be evaluated before making a decision. Cinder blocks are often more affordable, but not as long-lasting as concrete.
Gravity retaining walls
They are the simplest and earliest recorded type of retaining wall. Built of concrete, masonry, brick, blocks or mass cast-in-situ concrete, these hard-wearing structures rely on their large weight to resist toppling and sliding caused by the lateral earth pressure from the soil behind them.
Discover how the right retaining wall can reduce soil erosion, improve water drainage, and transform your property. Depending on the material, soil, and groundwater, a permanent retaining wall can last anywhere from 25 to 100 years.
Sometimes retaining walls are designed as cantilevers. These typically include reinforcement and rely on the combined strength of the concrete and reinforcement to resist bending at the base of the wall. In that case, plan on waiting seven days before placing the full depth of backfill.
Using a professional-grade fabric in retaining wall construction is important in ensuring the longevity of the wall.
With the permission of both property owners, a retaining wall can be built on property lines. But it's worth noting that the two parties still have responsibility for any of their actions that destabilises the wall's structural integrity.
A retaining wall without a footing may experience settlement, leaning, or failure over time. Footings help distribute the weight of the wall and its load, preventing excessive pressure on the soil and ensuring long-term stability.
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.
The average cost to build a retaining wall is $20 to $50 per square foot or $40 to $300 per linear foot. Installing a 50' long retaining wall costs $4,000 to $10,000 on average. Retaining wall labor costs $10 to $30 per square foot, and material prices are $5 to $20 per square foot on average.