How do I fix a sunken concrete garage floor in Moncton?

A sunken concrete garage floor in Moncton is most commonly caused by inadequate compaction of the granular base when the floor was originally poured, or by soil consolidation and moisture movement beneath the slab over time. The good news is that if the slab itself is structurally sound — not cracked into pieces or broken through — lifting and levelling is often the most cost-effective solution before considering full replacement.

Moncton's geology includes areas with varying soil conditions — from well-draining sandy soils in some neighbourhoods to softer, moisture-retaining soils closer to Petitcodiac River floodplain areas. Garages built on inadequately compacted fill soil — especially common in newer developments where the lot was graded with imported fill — are prone to settling as the fill material consolidates over the first 10-20 years. The garage floor slab may remain structurally intact while the soil beneath compresses, creating a void between the slab and the base.

Your first step is to assess the slab condition. Walk the floor and look for: major cracks wider than 3mm (1/8 inch), areas where the slab flexes or sounds hollow when walked on, sections that have broken into multiple pieces or show significant differential settlement (one section much higher than an adjacent section), and signs of ongoing moisture infiltration from beneath (efflorescence, damp spots after dry weather). A slab in multiple pieces with rebar showing is a replacement job. A slab that is sunken 1-3 inches but still monolithic and crack-free is a good lifting candidate.

Poly levelling or mudjacking are both appropriate for structurally sound sunken garage floors in Moncton. Poly levelling is often preferred for garage interiors because the smaller injection holes patch more cleanly, and the foam's waterproof properties help with any moisture that contributed to the sinking. Expect $5-$10 per square foot for poly levelling — a typical two-car garage floor (400-500 sq ft) would run $2,000-$5,000. Mudjacking costs less at $3-$6 per square foot but adds weight and is less water-resistant.

If the slab is beyond repair, full replacement of a two-car garage floor in Moncton runs $3,000-$5,000, including demolition and removal of the old slab, subgrade inspection and compaction, a minimum 4-inch air-entrained concrete slab with wire mesh or rebar on chairs, and proper control joints. Ensure the contractor specifies air-entrained mix for the new slab — a garage floor in Moncton exposed to de-icing salt tracked in on vehicle tires absolutely needs air entrainment to resist the salt-accelerated freeze-thaw cycling.

Before lifting or replacement, address any drainage issues causing the problem. Ensure downspouts discharge well away from the garage foundation, that the grade around the garage slopes away from the building, and that any water infiltration through the garage walls or floor joints is remediated. Lifting a slab without fixing the water pathway that caused the settlement is a temporary fix.

New Brunswick Concrete can match you with concrete lifting and repair professionals serving the Moncton, Dieppe, and Riverview area for a free on-site assessment.