Can I build my own concrete retaining wall in New Brunswick?

Small retaining walls under 2 feet in height are reasonable DIY territory in New Brunswick. Once you exceed 2 feet of retained height, the structural forces, drainage requirements, and NB's frost heave conditions make professional involvement strongly advisable.

A concrete retaining wall has to resist three forces simultaneously: the lateral pressure of the soil behind it, the hydrostatic pressure of groundwater, and the frost heave forces that New Brunswick winters generate with particular intensity. NB's 150+ annual freeze-thaw cycles create tremendous uplift and lateral pressure as saturated soil freezes and expands. A wall that is not properly designed -- with adequate thickness, reinforcement, footing depth, and drainage -- will crack, tilt, or fail. This happens gradually over years, then suddenly.

For a small decorative wall under 2 feet retaining a garden bed or gentle grade change, DIY using precast concrete blocks or poured concrete with a simple footing is achievable. The footing must still extend below the frost line -- minimum 4 feet below grade in southern NB -- even for a small wall. This is where many DIY retaining walls fail. A beautiful wall sitting on a shallow footing will heave, shift, and crack within the first two winters.

Drainage behind the wall is non-negotiable. Without a gravel drainage layer and perforated drain tile at the base of the wall, water accumulates behind the wall and dramatically increases the hydrostatic pressure it must resist. In spring when NB soils are saturated from snowmelt, a wall without proper drainage is under enormous stress. Install a 12-inch gravel drainage zone behind any retaining wall and direct the drain tile to daylight at the end of the wall.

NB Building Code requires a permit for retaining walls exceeding 4 feet (1.2 metres) in exposed height. Walls over 4 feet also require engineered drawings in most cases, showing proper reinforcement, footing design, and drainage. In Moncton, Fredericton, and Saint John, contact the city's building inspection department before breaking ground on any wall over 3 feet.

For a poured concrete retaining wall between 2 and 4 feet, costs run $25-$50 per linear foot per foot of height. A 20-linear-foot wall at 3 feet tall runs $1,500-$3,000 in materials for a DIY attempt, not including equipment rental for forming and placing the concrete. For walls in this range, the cost difference between DIY and professional is often narrower than homeowners expect, particularly when you factor in equipment rental, waste, and the risk of a failed pour.

Get professional help for any wall retaining more than 2 feet of earth, any wall near a property line, and any wall where failure could affect a structure, driveway, or neighbouring property. New Brunswick Concrete can match you with an experienced local contractor who understands NB frost and drainage conditions.