Linear extensibility describes shrink–swell behavior
Linear extensibility expresses a soil length change between defined moist and dry conditions as a percentage. GroundShiftCheck uses four screening bands: under 3%, 3% to under 6%, 6% to under 9%, and 9% or more. NRCS lists 0–30% as the valid LEP entry range. A value exactly at a boundary enters the higher band in this tool.
Clay content describes composition
Clay percentage describes the clay-sized fraction. It is not the same property as linear extensibility. Do not enter clay percentage into the LE interpreter or infer a building movement rate from it. The report lists clay as supporting information beside each reported layer.
Plasticity is a separate index
Plasticity index describes the difference between liquid and plastic limits; it is not a damage probability either. Keep the index, test context and soil depth with the result. Comparing two bare numbers from different properties can create a misleading ranking.
Interpret a value without inventing a diagnosis
Use the interactive interpreter to check an LE band and its boundaries. Include rated depth when you know it. The result explains the property and the evidence gap; it does not calculate foundation displacement, prescribe watering or decide whether repair is needed.
Sources and interpretation
USDA NRCS linear-extensibility definitions
Explanations and workflow are our own. This is educational screening, not a site investigation or engineering recommendation.