If your yard has a slope, drainage issues, or eroding soil, you've probably been told you need either a retaining wall or armour stone. Both solutions manage grade changes and prevent soil erosion, but they work differently, look different, and come with different price tags. Here's how to decide which one is right for your property.
What Is a Retaining Wall?
A retaining wall is an engineered structure designed to hold back soil at different elevations. In the GTA, most residential retaining walls are built using one of these materials:
- Concrete blocks (Allan Block, Versa-Lok): Interlocking modular units that stack up like oversized Lego. They're the most popular choice for residential projects because they come in various colours and textures, and they don't require mortar.
- Poured concrete: Stronger and more uniform, but requires formwork and curing time. Common in commercial and high-load applications.
- Timber/landscape ties: The most affordable option, but they have a shorter lifespan (10-15 years) and are prone to rot and insect damage.
Retaining walls require proper drainage behind them (usually a perforated pipe and gravel backfill) and, for walls over 4 feet, they typically need a structural engineer's design in Ontario.
What Is Armour Stone?
Armour stone refers to large, naturally quarried limestone or granite boulders, typically weighing between 500 and 3,000 pounds each. They're placed using an excavator and stacked or positioned to create a natural-looking retaining structure.
Unlike modular block walls, armour stone doesn't rely on an engineered interlocking system. Instead, the sheer mass of the stones holds back the soil. Each stone is selected and placed individually, with the operator choosing pieces that fit together naturally.
Retaining Wall: Pros and Cons
Pros:
- Clean, uniform appearance that complements modern homes
- Available in many colours, textures, and cap styles
- Can incorporate steps, curves, and corners precisely
- Well-documented engineering standards for tall walls
- Easier to build level and plumb on uneven terrain
Cons:
- Higher material cost per linear foot for premium blocks
- More labour-intensive installation (base preparation, levelling each course, backfill drainage)
- Can look artificial in natural or wooded settings
- Susceptible to frost heaving if base isn't deep enough
Armour Stone: Pros and Cons
Pros:
- Natural, rugged appearance that blends with the landscape
- Extremely durable -- limestone and granite last indefinitely
- Faster installation (no mortar, no precise levelling required)
- Often more affordable for short walls (under 3 feet)
- Low maintenance -- no joints to fail, no caps to shift
Cons:
- Requires heavy equipment (excavator) for placement
- Less precise -- gaps between stones can be uneven
- Not ideal for tall, straight walls where precision matters
- Each project looks unique, which can be a pro or con depending on your taste
Cost Comparison
In the Greater Toronto Area, here's a rough comparison for a typical residential project:
- Armour stone: $30-$60 per linear foot for walls under 3 feet, including material and installation
- Concrete block retaining wall: $40-$80 per linear foot for walls under 3 feet, including base preparation, material, drainage, and cap stones
- Walls over 4 feet: Both options increase significantly in cost, and engineering fees add $1,500-$3,000 to the project
These numbers vary based on access difficulty, soil conditions, and the specific materials chosen. Always get multiple quotes from contractors who specialize in the type of wall you're considering.
When to Choose Each Option
Choose a retaining wall when:
- You want a clean, architectural look
- The wall needs to be taller than 3 feet
- You're incorporating steps or seating into the design
- The wall runs along a property line and needs to be precisely placed
- You plan to build a patio or structure on top of the retained area
Choose armour stone when:
- You prefer a natural, organic appearance
- The grade change is moderate (under 3 feet)
- You want a low-maintenance solution that lasts a lifetime
- Budget is a primary concern for shorter walls
- Your property has a natural or cottage-style landscape
Can You Combine Both?
Absolutely. Many of our projects in the GTA use armour stone for lower-tier landscape borders and a modular block retaining wall for the main structural retention. This gives you the natural look where it's visible and the engineered strength where it matters most. It's one of the most cost-effective approaches for multi-level yards.