Retaining walls manage grade changes on your property — they hold back soil on sloped land, create usable flat areas, prevent erosion, and protect foundations from soil pressure. In Ottawa, retaining walls are common due to the varied terrain along the Rideau Canal, Ottawa River, and throughout neighbourhoods built on rolling hills. Common reasons Ottawa homeowners need retaining walls include: managing a sloped backyard to create a flat patio or play area, preventing soil erosion against the f...
Interlocking concrete block (e.g., Allan Block, Pisa, Versa-Lok): $25–$50 per square foot of wall face installed. The most popular choice in Ottawa. Engineered systems with built-in setback (batter) for structural stability. Wide variety of colours, textures, and sizes. A 50-linear-foot wall at 3 feet high (150 sq ft face) costs $3,750–$7,500. Natural stone (armourstone, limestone, granite): $35–$65 per square foot of wall face installed. Armourstone (large quarried blocks, 1–2 tonnes each) is ...
Engineering requirements: Retaining walls over 1 metre in exposed height in Ottawa require design by a Professional Engineer (P.Eng.). Engineering fees cost $1,000–$3,000 depending on wall complexity, soil conditions, and site access. The engineer provides sealed drawings specifying wall dimensions, reinforcement, drainage, and foundation requirements. Drainage behind the wall: Every retaining wall must manage water — hydrostatic pressure (water pressure behind the wall) is the #1 cause of reta...
For walls under 1 metre: Experienced landscaping companies with retaining wall portfolios can handle these projects. Look for companies that demonstrate proper drainage installation (crushed stone backfill, drainage pipe) — many landscapers skip drainage on short walls, leading to premature failure. For walls over 1 metre: Hire a contractor experienced with engineered retaining wall systems. They should work with a P.Eng. for the design and have experience with the specific wall system being us...
Timber walls cost $15–$30 per sq ft of face. Concrete block costs $25–$50. Natural stone/armourstone costs $35–$65. Poured concrete costs $30–$55. A typical 50-foot wall at 3 feet high costs $3,000–$9,750 depending on material.
Retaining walls over 1 metre (3.3 feet) in exposed height require a City of Ottawa building permit and engineering design by a P.Eng. Walls under 1 metre typically don't require a permit but must comply with property setbacks.
The #1 cause is inadequate drainage — water pressure builds behind the wall, pushing it forward. Other causes include insufficient foundation, poor compaction, inadequate wall mass for the retained height, and tree roots.
Concrete block and natural stone walls last 50+ years with proper construction and drainage. Poured concrete walls last 50–100 years. Timber walls last 15–20 years. Proper drainage is the key to longevity regardless of material.