Footings transfer column or wall load into soil, and small mistakes in load basis, soil classification, settlement assumptions, groundwater, frost, or reinforcing details can become structural failures. A planning calculator can help frame the questions, but it cannot replace the adopted code, geotechnical report, project drawings, or a licensed structural engineer.
This guide explains the limited screening ideas behind the ToolGrit footing app: local bearing stress, uniaxial eccentricity, one-way shear, punching shear, and flexure. The app deliberately labels ACI, IBC, ASCE, ASTM, CRSI, geotechnical, and AHJ items as source gaps unless the user has current project-specific sources.
Bearing Pressure Is Only One Screen
A simple concentric screen divides vertical service load by footing area. A uniaxial eccentricity screen estimates whether pressure remains across the base or whether a partial-contact warning should be reviewed. Those formulas are useful for early sensitivity checks, but they do not prove settlement performance, soil classification, frost protection, groundwater behavior, slope stability, or construction acceptance.
The app expects the user to supply the service load and allowable bearing value. It does not calculate footing self-weight, overburden, buoyancy, surcharge, live-load reduction, ASCE load combinations, or geotechnical settlement limits.
Footing Bearing Pressure Calculator
Check bearing pressure for spread footings with eccentric loading per ACI 318 and IBC Table 1806.2. One-way shear, two-way punching shear, and flexural reinforcement checks included.
Do Not Treat a Soil Selector as a Soil Report
The app includes a small local IBC-style vertical bearing snapshot because it is useful for screening examples. It is not a soil classification tool and does not decide when presumptive values are allowed. Fill, organic soils, expansive soils, groundwater, poor compaction, nearby excavations, slopes, seismic liquefaction risk, and settlement sensitivity can make a simple value unusable.
For real projects, the allowable bearing value should come from a current geotechnical report or a value accepted by the building official for the adopted code and site conditions.
Concrete Shear Checks Need Current Code Review
One-way shear and two-way punching shear are strength-design checks that depend on effective depth, concrete strength, column geometry, load basis, and the adopted concrete code. The app keeps a simplified local implementation for early screening, but it does not reproduce the full ACI code, commentary, exceptions, or detailing requirements.
Edge and corner columns, eccentric loading, transfer elements, seismic requirements, openings, construction joints, dowels, and unusual geometry can all invalidate a simplified screen.
Rebar Suggestions Are Not Detailing
The app estimates a local flexure demand and suggests a rough bar count and spacing from cached bar-area rows. That is not a reinforcement detail. Real footing reinforcement also depends on development length, dowel transfer, concrete cover, exposure, bar grade and coating, seismic detailing, congestion, lap locations, construction tolerances, and the project specification.
Before construction, reinforcement should be shown on structural drawings and reviewed with the current concrete code, ASTM bar specification, CRSI or firm standards, inspection requirements, and the engineer of record.