We had a 6-foot grade change at the rear of our Oakville lot — the previous owners had managed it with a rotting timber wall that was visibly leaning. We replaced it with an armour stone retaining wall. This was a significant project.
Why armour stone:
We got quotes for segmental block (Allan Block), poured concrete, and armour stone. The naturalistic look of armour stone suited our backyard better than the engineered look of block. And for a wall this height (1.8 metres), armour stone mass is an inherent advantage.
Engineer requirement:
Oakville: permit required for retaining walls over 1.0 metre. We were at 1.8m. Hired a geotechnical engineer: $2,400 for soil assessment and wall design. The engineer designed the footing depth, batter (backward lean for stability), and drainage system.
Permit:
Oakville building permit: $480
The build:
- Excavation (6 feet below grade for footing and drainage install): $3,200
- 4-inch perforated pipe behind wall in granular fill, daylighting at ends: $1,800
- Armour stone supply (local quarry, rounded field boulders): $8,400
- Armour stone placement (excavator + operator, 2 days): $4,200
- Backfill and grade restoration: $1,600
Total: $22,080 (including engineer and permit)
The result:
A 25-foot long, naturally integrated stone wall that looks like it’s been there forever. The engineer re-inspected after completion — signed off immediately. The wall has gone through two freeze-thaw cycles with zero movement.
The grade differential is now beautifully managed with a planted slope above the wall. The project transformed the backyard from an unusable slope to a flat usable area.