How much does a concrete slab foundation for a garage cost in Dieppe New Brunswick?

A concrete slab foundation for a garage in Dieppe, NB typically costs between $8,000 and $18,000, depending on the garage size, the foundation type (thickened-edge slab versus full frost walls with a slab), and site conditions. For a standard two-car garage (24x24), expect to pay $10,000 to $16,000 for the complete foundation package including excavation, forming, reinforcement, vapour barrier, concrete, and finishing.

The critical factor that drives foundation costs in Dieppe — as in all of New Brunswick — is frost depth. The frost line in the Greater Moncton/Dieppe area extends 4 to 5 feet (1.2 to 1.5 metres) below grade, and every garage foundation must extend below this depth or face heaving, cracking, and structural failure within the first few winters. There are two primary approaches to meeting this requirement.

The first is a full frost wall foundation with a poured slab floor. This involves excavating a trench around the garage perimeter to below frost depth, pouring concrete footings (minimum 16 inches wide and 8 inches thick), building frost walls up to grade level, backfilling, and then pouring a 4-inch concrete slab inside the walls. For a 24x24 two-car garage, this approach uses approximately 7 to 10 cubic metres of ready-mix concrete — 3 to 6 cubic metres for the footings and frost walls, and 4 to 5 cubic metres for the slab. At $200 to $280 per cubic metre for ready-mix concrete delivered in the Dieppe area, the concrete material alone runs $1,400 to $2,800. Add excavation ($1,500 to $3,000), forming and reinforcement ($2,000 to $4,000), and finishing ($2,500 to $5,000), and the total for a full frost wall foundation with slab comes to $12,000 to $18,000.

The second approach is a thickened-edge slab (also called a monolithic slab or turned-down slab). This design thickens the slab perimeter to 12 to 16 inches below grade, with rigid foam insulation protecting the outer edge from frost penetration. The interior slab remains the standard 4 inches thick. This approach uses less concrete and requires less excavation, bringing the cost down to $8,000 to $13,000 for a 24x24 garage. However, not all municipalities in the Greater Moncton/Dieppe area accept this foundation type for garages — you must verify with the local building inspection department before committing to this design. If approved, it offers meaningful savings while still protecting against frost heave.

Several details are essential regardless of which foundation type you choose. A 6-mil polyethylene vapour barrier must be placed beneath the concrete slab before pouring. This $200 to $400 detail prevents ground moisture from wicking up through the concrete, which would leave you with a perpetually damp floor, peeling floor coatings, and mildew on anything stored on the slab. It is impossible to add this barrier after the slab is poured, so it is a one-chance-only detail. The slab should also include welded wire mesh or rebar reinforcement to control cracking — a standard 6x6 W2.9xW2.9 welded wire mesh costs $150 to $300 for a two-car garage and significantly reduces the size and frequency of shrinkage cracks.

Concrete finishing affects both the cost and the long-term usability of your garage floor. A basic broom finish runs $6 to $10 per square foot and provides adequate traction for vehicle traffic. If you plan to apply an epoxy or polyaspartic floor coating later, ask your contractor to power-trowel the slab to a smooth finish — this provides a better bonding surface for coatings. The slab should be sloped slightly toward the overhead door (approximately 1/8 inch per foot) to allow snowmelt and wash water to drain out.

Dieppe's soil conditions in much of the developed area are generally favourable for garage foundations — relatively stable, well-drained soils without the rock challenges found in some other NB communities. However, areas closer to the Petitcodiac River or in low-lying zones may have a higher water table or softer soils that require additional gravel base preparation or drainage tile around the footings. A contractor experienced with local conditions will know what to expect on your specific lot.

Foundation work is never a DIY project. Improper forming, insufficient reinforcement, shallow depth, or poor concrete finishing will result in a foundation that fails — and the cost to demolish and replace a failed garage foundation exceeds the original cost of doing it right. Get at least three quotes from contractors experienced with garage foundations in the Greater Moncton/Dieppe area. New Brunswick Garages can help match you with local professionals for free estimates through the New Brunswick Construction Network.