The strongest type of retaining wall is generally considered to be a gravity wall. These walls are made of heavy materials, such as concrete or stone, that rely on their weight to resist the pressure of the soil behind them.
Concrete retaining walls are typically the strongest. Gravity walls use mass to resist pressure. Cantilevered walls rely on reinforced structures for strength.
The 1/3 rule is a general guideline for stability: About 1/3 of the wall's total height should be buried below ground. This helps the wall resist the pressure from soil and moisture behind it.
If you are for the most durable retaining wall material, here at Jamesco Group, we think concrete blocks, concrete sleepers, gabion walls, and natural stone are all excellent choices. They offer longevity and strength, and can withstand the test of time.
Natural stone and reinforced poured concrete typically last the longest, often 50+ years with little maintenance. What's the cheapest retaining wall material? Timber is cheapest upfront, but concrete block offers the best balance of affordability and lifespan.
Even a 3-foot retaining wall benefits from a proper retaining wall drainage system. Without adequate drainage, water buildup behind the wall increases hydrostatic pressure, leading to structural failures like cracks, bulges, or total collapse.
Seven common mistakes when installing retaining wall blocks include poor base preparation, inadequate drainage, not using proper backfill, failing to compact soil, improper alignment of blocks, ignoring wall height limits, and neglecting to use geogrid reinforcement when needed.
What Are The Three Types Of Retaining Walls?
Decomposed granite is a type of gravel made from 100% pulverized granite. This type of gravel is ground into fine particles and will pack together to form a gravel that hardens like concrete when compacted.
Short retaining walls, such as those around 2 feet tall, may not always require a concrete footing, but the necessity depends on several factors, including soil type, drainage, and the materials used. Without a proper foundation, even small walls are susceptible to shifting, leaning, or failure over time.
A common mistake in DIY wall construction is underestimating how deep to dig the retaining wall trench. The rule of thumb is to bury about 10% of the wall's height plus an additional 4–6 inches for the gravel base.
A 4-foot wall can range from $600 to $150 per linear foot, depending on the material, with drainage adding extra cost. Drainage is non-negotiable for any retaining wall, even at 4 feet, to prevent water-related damage.
If between 1.5-2 metres from boundary, maximum wall height 2 metres. If greater than 2 metres from boundary, maximum wall height 3 metres. If more than 600mm above or below ground level, are contained by a structural support.
Alternatives to retaining walls with slope grading, riprap, anchored walls, vegetation, erosion control mats, and piling systems.
A retaining wall ranges in height from 900 millimetres to 1.8 metres. The part of the retaining wall that exceeds the maximum allowable height of 1.5 metres will require a building consent.
An 8" x 16" standard cinder block is required to hold up at least 2000 pounds per square inch according to ASTM International. While this means that a 64-square-inch cinder block can hold 128,000 pounds, the actual cinder block weight limit is less than that.
Water is the most common enemy of concrete surfaces. When water penetrates the surface of concrete, it can cause it to crack and weaken. This is especially true in colder climates where water can freeze and expand, creating even more damage.
Most residential concrete slabs require 4-6 inches of compacted crushed stone underneath. Heavy-duty applications like driveways may need 6-8 inches, while commercial projects often require 8-12 inches or more. Always compact the stone in 2-3 inch lifts for uniform density throughout the base layer.
Poor Drainage: Inadequate drainage behind the retaining wall can result in excessive pressure buildup, leading to instability and eventual failure. Soil Erosion: Gradual erosion of soil weakens the foundation of the retaining wall, causing it to lean or collapse over time.
Choose a DIY-friendly building material. Retaining walls can be made from wood, bricks, natural stones or concrete blocks. For DIYers, it's easiest to use concrete retaining wall blocks that interlock. Interlocking blocks fit together and add extra security to the wall.
Stone retaining walls can be more expensive due to material and labor costs. They are ideal for projects where appearance and durability are priorities.
Stability depends heavily on footing depth, which is usually 1/2 to 1/3 of wall height, depending on soil type and retaining wall materials.
The four most common failure modes for retaining walls include sliding, overturning, bearing capacity, and global stability. Sliding A wedge of soil forms behind the wall, and the pressure it forms pushes the wall away from the soil. The wall stays intact, but the ground behind collapses.
Foundation bearing (gravity case)
For the following simplified procedure, the “middle third rule” is applied, whereby the wall foundation is dimensioned so that the resultant vertical force acts through the “middle third” of the footing.