Expansive Soil in St. Clair County, MI
Does St. Clair County, MI have expansive soil? Partly: the dominant shrink-swell rating for St. Clair County, MI is Moderate, with 42% of the county's mapped soil acres in the Moderate class.
Soil class breakdown for St. Clair County
What a Moderate rating means for a slab foundation
Soils in this class show measurable shrink-swell behavior. In long dry spells the soil shrinks and can pull support away from the edges of a slab; wet seasons swell it back. Most homes do fine, but keeping moisture consistent around the foundation, with working gutters, positive drainage, and stable landscaping, matters more than it does in low-rated areas.
This is a county-level rating built from USDA soil survey data, not a parcel-level geotechnical assessment. Soils change from lot to lot; a geotechnical engineer or foundation professional can assess the ground under your specific property.
Foundation repair across Michigan
We do not yet have a covered city mapped to St. Clair County. These Michigan cities have provider listings and cost guides:
Methodology and sources
This rating is computed from USDA NRCS SSURGO soil survey data
:
for each soil component we take the maximum linear extensibility percent
(lep_r) among horizons starting within 0 to 100 cm of the surface, apply the
NRCS National Soil Survey Handbook Part 618 class limits (Low under 3 percent, Moderate 3
to under 6, High 6 to under 9, Very High 9 and above), assign each map unit the class
holding the plurality of component percent, and sum map unit acres per class across the
county, excluding unmapped and water areas.
- Data source: USDA NRCS SSURGO via Soil Data Access
- Class limits: NRCS National Soil Survey Handbook, Part 618
- Survey coverage: 96% of county map acres
- Computed: 2026-07-05
- Note: max lep_r over horizons with hzdept_r<100cm (major components only), comppct_r plurality per mapunit, county rollup by muaoverlap.areaovacres, class limits NSSH Part 618, shares are fractions of rated acres
Full methodology · All Michigan counties · Look up another ZIP
FAQ
Does St. Clair County, MI have expansive soil?
Partly: the dominant shrink-swell rating for St. Clair County, MI is Moderate, with 42% of the county's mapped soil acres in the Moderate class.
What does a Moderate rating mean for a slab foundation?
Soils in this class show measurable shrink-swell behavior. In long dry spells the soil shrinks and can pull support away from the edges of a slab; wet seasons swell it back. Most homes do fine, but keeping moisture consistent around the foundation, with working gutters, positive drainage, and stable landscaping, matters more than it does in low-rated areas.
Is this a parcel-level soil report?
No. This is a county-level rollup of USDA NRCS SSURGO soil survey data for St. Clair County, MI. Soils vary lot to lot, so a geotechnical engineer or foundation professional should assess your specific property before you make repair decisions.
How much does foundation repair cost near St. Clair County?
Pricing depends on the repair method and how far the movement has progressed, from sealing a single crack to installing piers. SlabLocal publishes city-level foundation repair cost guides with sourced ranges for cities across Michigan.