What type of rebar should be used in NB foundations?

For New Brunswick foundation work, standard 15M (metric #5, 5/8-inch diameter) Grade 400 deformed rebar is the most common specification — used for foundation walls, grade beams, and heavily loaded structural elements. 10M (metric #3, 3/8-inch) is used for lighter applications and tie bars. Epoxy-coated rebar is recommended in high-moisture or coastal environments.

Rebar in Canada is classified by bar diameter (10M, 15M, 20M) and yield strength grade (Grade 400 = 400 MPa yield strength is standard). Deformed rebar — the type with the ridges and bumps on the surface — bonds far better to concrete than plain smooth bar, and is required for all structural applications.

Foundation wall reinforcement in a typical NB residential home uses 15M vertical bars at 200–300 mm centres and 10M horizontal bars at 400–600 mm centres, depending on wall height, soil pressure, and the engineer's design. The specific spacing and sizing must be engineered — residential foundation plans should always be drawn or reviewed by a structural engineer or conform to prescriptive requirements in the NB Building Code for standard residential construction.

Why NB foundations need good reinforcement: Frost heave, hydrostatic pressure from spring thaw, and expansive clay soils (common in parts of the Moncton, Fredericton, and Miramichi areas) all place lateral loads on foundation walls. Adequate rebar prevents cracking, bowing, and wall movement. A foundation wall without proper reinforcement relies entirely on the concrete in tension — which is the concrete's weakest direction.

Corrosion is a real concern in NB foundations exposed to groundwater, particularly near the coast (Saint John waterfront, Shediac, Bathurst coast) or in areas with high water tables. Moisture diffuses through concrete over decades, eventually reaching the rebar and initiating corrosion. When rebar corrodes, it expands, cracking the surrounding concrete from the inside. Epoxy-coated rebar ($0.50–$1.00 per foot premium) or stainless steel rebar is a worthwhile investment in high-moisture foundation environments — especially for below-grade exterior walls that will be in contact with soil and groundwater for the life of the building.

Concrete cover over rebar is critical: CSA A23.1 requires a minimum of 50 mm (2 inches) of concrete cover over rebar in foundations and 75 mm (3 inches) in slabs on grade exposed to the ground. Insufficient cover allows moisture to reach the steel faster. Rebar chairs and spacers must be used to maintain cover during the pour — a detail worth verifying with your contractor.

For foundation rebar work in NB, always hire a qualified concrete contractor and ensure the design is engineered for your specific site conditions.