Roof Pitch & Rafter Calculator implementation

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

t4-055

Effect

Computation or source lookup only

Input and validation requirements

The stated formula has an undefined division when run = 0, and the span-versus-run input representation creates a branch where identical numeric dimensions produce different results. Negative overhang also exposes an unresolved sign convention.

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": {
    "run": 12,
    "rise": 6,
    "overhang": 1,
    "unit": "ft"
  },
  "expected_outputs": {
    "pitch_ratio": 0.5,
    "pitch_label": "6:12",
    "angle_degrees": 26.565051,
    "rafter_length": 14.416408,
    "length_unit": "ft"
  },
  "working": "pitch = rise / run = 6 / 12 = 0.5, so the normalized label is 0.5 * 12 = 6, or 6:12. angle = atan(0.5) * 180 / pi = 26.565051 degrees. Base rafter = sqrt(12^2 + 6^2) = sqrt(144 + 36) = sqrt(180) = 13.416408 ft. Rafter length = 13.416408 + 1 = 14.416408 ft."
}

Other records

Sources and evidence

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

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json