The best overall material for a retaining wall is interlocking concrete block (or modular segmental block). It balances high durability, cost-effectiveness, and DIY-friendliness. For sheer structural strength, poured concrete is best, while natural stone offers unmatched, premium aesthetics.
For the absolute strongest retaining wall, poured reinforced concrete is unmatched. It offers monolithic strength that can hold back massive amounts of earth, especially for high, multi-tiered, or steep-slope applications.
Poured reinforced concrete and natural stone (such as granite or limestone) retaining walls last the longest, often easily exceeding 505050 to 100100100 years. While natural stone is arguably the most permanent, poured concrete offers unmatched structural strength and durability when properly reinforced with steel rebar.
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.
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.
Yes, a 3-foot retaining wall absolutely needs drainage. While it is a relatively short wall, trapping water behind it creates immense hydrostatic pressure. Without proper drainage, this pressure, combined with heavy saturated soil, can cause the wall to bulge, crack, or collapse.
Our professional building inspectors often find that retaining wall failures boil down to poor planning, poor installation, and, most commonly, poor drainage.
For most standard landscape retaining walls (under 3–4 feet), your total digging depth should be 12 to 15 inches. This allows for a 6-inch compacted gravel base and embeds the first course of blocks (or roughly 10% to 15% of the total wall height) into the ground.
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.
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.
A pressure-treated wood retaining wall typically lasts between 15 and 30 years. However, the exact lifespan largely depends on local climate, soil moisture, and whether proper drainage was installed.
The 4 main types of retaining walls are gravity, cantilever, sheet pile, and anchored walls. Each uses a distinct engineering mechanism to hold back soil and combat the natural pressure of the earth.
Disadvantages of Retaining Walls
Retaining walls require careful planning and engineering to ensure they are strong enough to hold back the soil. Another disadvantage of retaining walls is that they can be difficult to maintain. Retaining walls can be susceptible to erosion, cracking, and other types of damage.
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.
What's the cheapest retaining wall material? Timber is cheapest upfront, but concrete block offers the best balance of affordability and lifespan.
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.
If you want to manage soil and slopes without building a traditional retaining wall, you can use landscaping techniques like terraced grading, riprap rock placement, or geogrid-reinforced vegetated slopes. These alternatives often blend naturally into your yard and are typically much easier and cheaper to install.
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.
Stone retaining walls can be more expensive due to material and labor costs. They are ideal for projects where appearance and durability are priorities.
All walls need and should have drainage plus the proper amount of stone backfill to prevent push from freeze/thaw.
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.
One of the leading causes of retaining wall failures is improper drainage. There are many reasons for this, but one main reason is that saturated soils behind walls cause excessive weight. This additional surcharge may cause the wall to lean outward and eventually collapse.
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.
Retaining walls need drainage to prevent the buildup of trapped water, which can exert massive hydrostatic pressure, saturate the backfill, and lead to structural failure, bowing, cracking, or collapse.
Retaining walls and slopes can collapse
Storms, floods, and earthquakes can produce landslides, causing sloped land and retaining walls to collapse and cause damage. Like any part of your house or property, retaining walls and some slopes need to be maintained.