How the score is built.
Six measured soil factors, one national database, and a weighting that changes with the question. This page is the whole method, stated plainly enough to be checked.
The six-factor stack.
Every score on this site starts from the same six measured factors, read straight from the national soil survey for the map units under your parcel.
Shrink-swell potential
Linear extensibility: how much the ground moves as it wets and dries. The driver of foundation heave.
Corrosivity
Rated attack on buried steel and concrete. What fails what you build and bury.
Slope
Gradient from the elevation model. Grading cost, stability, and drainage behavior.
Drainage class
How water moves through the profile, from excessively drained to ponded.
Depth to water table
How close saturation sits to the surface. Excavation, septic, and wetland exposure.
Flooding frequency
Mapped flood recurrence on the parcel, independent of any insurance zone.
One factor stack, reweighted
An insurer cares about ground movement. A pipeline operator cares about corrosion. A lender cares about productivity. The factors do not change; the weighting does. Each product reweights the same six axes toward the failure mode its buyer actually pays for, so every score stays traceable to the same measured layer.
Weighted toward shrink-swell and flooding: the drivers of ground movement.
Same six measured factors. The weighting changes, the score changes, the customer changes. One database underneath.
Public data, cited every time.
Four public layers carry every number on the site. Nothing proprietary sits between a score and its source.
SSURGO
The national soil survey's map-unit database: 967,000 records across 4,089 survey areas, 134 tables of measured and rated soil properties.
KSSL
Characterized lab pedons from the Kellogg Soil Survey Laboratory: the physical and chemical ground truth beneath the mapped polygons.
the federal soil API
The federal query service the survey itself runs. Every number we publish can be re-pulled from the same endpoint we used.
Elevation & terrain
Slope, curvature, and wetness derivatives from national elevation data, joined to the soil layers where terrain drives the answer.
Map-unit scale. Screening-grade. Borings still govern final design.
The soil survey maps the ground in units, not points. Our scores read those units, so they are screening-grade: built to rank parcels, flag the failure modes, and tell you where to spend your geotechnical budget, not to replace it. Final foundation design still rests on borings drilled on the actual building pads.
We state that plainly because it is why the work holds up. A score that admits its resolution is one you can put in front of a lender, a regulator, or a jury.