Source: https://guthlabs.ai/docs/instruments/footing-size-calculator-preliminary/implementation/

instrument implementation / implementation-contract

# Footing Size Calculator (Preliminary) implementation

A source-bound implementation contract for Footing Size Calculator (Preliminary); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-131

**Effect**: Computation or source lookup only

## Input and validation requirements

The plain formula has no stated input validation or load-sign convention. Zero or negative allowable pressure can cause division-by-zero or invalid negative areas, zero load produces a nonphysical zero footing, and a signed compressive load can produce an undefined square root.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "P": 600,
    "P_unit": "kN",
    "qallow": 200,
    "qallow_unit": "kPa",
    "shape": "square"
  },
  "expected_outputs": {
    "required_area": 3,
    "required_area_unit": "m²",
    "square_side": 1.73205,
    "square_side_unit": "m"
  },
  "working": "1. Since 1 kPa=1 kN/m², qallow=200 kN/m². 2. A_req=P/qallow=600 kN ÷ 200 kN/m²=3 m². 3. Square side=√A_req=√3 m=1.73205 m."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/footing-size-calculator-preliminary/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/footing-size-calculator-preliminary/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/footing-size-calculator-preliminary/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`