Garage floor crack widening — Leiden, Zuid-Holland

A crack in a concrete garage slab that grows wider over time usually signals that the subgrade beneath the slab is settling unevenly or that freeze-thaw cycles are heaving sections apart. Thin hairline cracks are common in new concrete, but once a crack exceeds 1/4 inch wide or one side is noticeably higher than the other, the slab is shifting structurally. Water infiltration through the widening crack can accelerate erosion of the gravel base below, creating voids that cause further settlement. A concrete mason can assess whether the slab needs crack injection with epoxy or polyurethane, partial slab replacement, or mudjacking to lift settled sections back to grade.