Do retaining walls need rebar in New Brunswick?

Yes — any poured concrete or concrete block (CMU) retaining wall over 2 feet high in New Brunswick should include rebar reinforcement, and walls subject to NB's frost conditions and soil pressures should be reinforced from the ground up regardless of height. The combination of lateral soil pressure, hydrostatic pressure from spring thaw, and frost heave forces makes unreinforced concrete retaining walls a poor choice for the NB climate.

Plain (unreinforced) concrete is strong in compression but weak in tension. A retaining wall resists the horizontal push of retained soil by acting as a cantilever or gravity structure, and that resistance creates bending forces in the wall that put the soil-facing side in tension. Without rebar to resist tension, plain concrete will crack horizontally under these bending forces — usually within the first few years if the soil is saturated. In NB, where spring thaw produces the heaviest loads, unreinforced walls crack and then allow frost penetration through those cracks, rapidly accelerating deterioration.

For poured concrete retaining walls, the standard NB practice is vertical rebar (#10M or #15M depending on wall height and soil conditions) at 12-16 inch centres, extending from the footing into the wall. Horizontal rebar or ties are added to hold the verticals in position and provide lateral confinement. For walls over 3 feet, most experienced contractors also add horizontal rebar at the base, mid-height, and top. The entire rebar assembly must have adequate concrete cover (minimum 50-75 mm on the soil-facing side) to prevent corrosion — rebar near the soil-facing surface of a wet NB wall will rust and spall the concrete if cover is insufficient.

For CMU (concrete block) walls, vertical reinforcing bar is placed in the hollow cores and the cores are grouted solid with concrete. This creates a reinforced masonry system that is functionally similar in strength to a poured wall. Horizontal joint reinforcement (ladder wire or truss wire) is installed every 2-4 courses to distribute loads and control cracking.

The only common exception is low gravity-mass walls — walls under 24 inches using large segmental blocks (concrete landscape blocks 40-60 lbs each), where the wall's own weight provides stability without reinforcement. These are acceptable for low landscaping terraces with gentle slopes behind them. Anything above 24 inches, anything retaining a significant slope, and anything near a structure or property line should be reinforced.

For retaining walls in Bathurst, Miramichi, and northern NB where frost depths approach 4.5-5 feet and winters are more severe, the case for proper reinforcement is even stronger. The cost savings from skipping rebar on a retaining wall are a false economy in NB — rebuilding a failed wall costs far more than doing it properly the first time.

New Brunswick Concrete can connect you with experienced retaining wall contractors across the province who will ensure proper reinforcement for your site conditions.