Retaining Walls

Concrete retaining walls solve critical grading and drainage challenges on New Brunswick properties while adding functional outdoor space and visual structure to sloped landscapes. NB's terrain varies from the flat Tantramar Marshes to the steep river valleys of the Saint John, Miramichi, and Petitcodiac, and many residential lots require retaining walls to create level areas for patios, driveways, gardens, and building pads. The NB Building Code requires that any retaining wall over 1.0 metre (approximately 3.3 feet) in exposed height be designed by a licensed professional engineer, and walls over 1.5 metres typically require a building permit from your municipal government. This is not bureaucratic formality — retaining walls must resist enormous lateral forces from the soil they hold back, and those forces increase dramatically during NB's spring freeze-thaw season when saturated soil behind the wall freezes, expands, and pushes against the structure with hydraulic force. Poured concrete retaining walls are the strongest and most durable option for NB applications. A typical residential poured concrete retaining wall features a T-shaped or L-shaped footing that extends below the frost line (1.2-1.5 metres in NB) to prevent heave, a stem wall of 200-300mm (8-12 inch) thickness depending on height and soil pressure, horizontal and vertical steel reinforcement sized by an engineer to resist bending and shear forces, and a granular backfill zone with weeping tile drainage behind the wall to relieve hydrostatic pressure. The drainage behind an NB retaining wall is arguably the most critical design element — without it, groundwater and snowmelt build up behind the wall, freezing in winter to create massive ice lenses that can push even heavily reinforced walls out of plumb. Weeping tile at the footing level, wrapped in filter fabric and surrounded by clear drainage stone, channels water to daylight outlets or storm connections. Weep holes through the wall face at regular intervals provide additional pressure relief. Alternative retaining wall types common in NB include concrete block (segmental retaining wall units like Allan Block or Redi-Rock) that interlock and rely on mass and setback for stability, and cast-in-place architectural concrete walls that can be formed with decorative textures, board-formed wood grain patterns, or smooth architectural finishes for visible applications. For walls under 1.0 metre, precast concrete garden wall blocks are a cost-effective DIY-friendly option, though professional installation ensures proper base preparation and drainage even at lower heights. NB pricing for poured concrete retaining walls runs $40-$80 per square foot of wall face for engineered walls including excavation, footings, forming, pouring, waterproofing, drainage, and backfill. A 40-foot-long wall at 4 feet exposed height (160 square feet of face) costs $6,400 to $12,800. Segmental block walls run $25-$50 per square foot of face installed. Engineering fees for walls requiring design add $1,500 to $4,000 depending on complexity and site conditions.

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