Retaining wall blocks are angled—or "tilted" backward into the hill—to provide structural stability. This backward lean, known as "batter," allows gravity to pull the wall's weight into the retained soil. It dramatically increases the wall's ability to resist lateral earth pressure and prevent 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.
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.
Straight retaining walls are more budget-friendly, faster to install, and ideal for modern homes with linear architecture or geometric outdoor spaces. Curved designs offer a naturalistic, organic look that blends with irregular terrain, while straight walls provide clean lines suited to contemporary aesthetics.
Laying the Retaining Wall Blocks
Begin to place the retaining wall units. Blocks must always be off set ½ unit so that the joints are staggered.
Fixing a leaning retaining wall depends on the severity. For minor leans (≤3is less than or equal to 3≤3 inches), stabilize the wall using Helical Tiebacks or Wall Anchors. For severe leans or structural damage, you will need to excavate, correct the drainage, and Rebuild the Wall completely.
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.
A cinder block retaining wall typically lasts 40 to 100 years. Its longevity depends heavily on soil pressure management, moisture control, and the structural integrity of the base.
Yes, a 2-foot retaining wall should have drainage to ensure long-term stability and prevent failure. While small, 2-foot walls can still trap water and build up significant hydrostatic pressure, leading to bowing, cracking, or tipping.
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.
The most affordable and beginner-friendly retaining wall options are interlocking concrete blocks, treated timber, or stacked cinder blocks. These materials typically cost between $2 and $6 per block, making them ideal for DIY projects. Always ensure proper soil drainage and check local building codes for walls over 3 feet tall.
Yes, you should fill hollow retaining wall blocks with gravel. This process is known as core filling.
Our professional building inspectors often find that retaining wall failures boil down to poor planning, poor installation, and, most commonly, poor drainage.
Yes, a retaining wall should always be built true level horizontally, regardless of the slope of your yard. Failing to level the blocks or stones can cause structural failure, as gravity will constantly push the weight downhill.
Homeowners insurance covers a retaining wall collapse only if the collapse is directly caused by a "named peril" listed in your policy, such as a vehicle hitting the wall, a lightning strike, or an explosion. If the collapse resulted from normal wear and tear, poor maintenance, erosion, or the weight of saturated soil, it will not be covered.
Most all of the retaining walls I've seen are straight. An arch can be strong but not when the pressure is pushing outward. Although, you could do both. If you're building the wall, it's your choice.
A deadman anchor is a structural component buried in the soil behind a retaining wall and connected to it via a tieback (like a cable, threaded rod, or timber tie). It uses passive soil pressure and dead weight to resist the outward pressure of retained dirt, preventing the wall from bowing or leaning over.
Building a 90-degree corner with retaining wall blocks is easiest if your manufacturer offers specialized corner blocks. If not, you can easily modify standard blocks. Always start at the corner and build outward to ensure your wall locks together correctly.
Yes, a 2-foot retaining wall generally needs a footing. However, "footing" means different things depending on how the wall is built. Instead of a deep, poured-concrete foundation, shorter walls usually rely on a compacted aggregate base or a single buried row of blocks.
What's the cheapest retaining wall material? Timber is cheapest upfront, but concrete block offers the best balance of affordability and lifespan.
Concrete blocks can be prone to water seepage.
Concrete blocks can cause seepage damage in areas with high water tables. Concrete blocks are strong but porous and allow water to penetrate. Water is persistent and will seek the path of least resistance. It can eventually make its way through walls and cause damage.
Treated Lumber Retaining Walls—Depending on grade and drainage, plan for 10–40 years. Above-ground sections may last around 20 years, but when lumber contacts moist soil with inadequate sealing, the clock ticks much faster.
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.