In the older parts of Arlington Heights, a detached garage slab may simply be original construction with a thinner base than we’d recommend now. Closer to downtown, alleys and older drainage patterns can also direct more water toward a garage than the original builders planned for. Farther from downtown, in homes built from the 1950s onward, we more often see settling tied to a specific cause: a gutter downspout, a sump pump discharge line, or a slab poured a bit too close to a slope.