Source: https://guthlabs.ai/docs/instruments/drywall-sheet-calculator/mechanism/

instrument mechanism / verified-clean

# Drywall Sheet Calculator mechanism

The inspectable method record for Drywall Sheet Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The sheet-count formula passes under the stated unit and percentage assumptions, but the spec is not complete enough for a fully honest implementation because screw/joint-compound outputs are claimed without formulas and area treatment for openings is unspecified. The exact review blockers are: waste% encoding, mixed-unit handling, gross-versus-net area, and undefined screw/joint-compound calculations.

- The sheet-count formula is standard and correct when area and sheet_area use the same units and waste_percent is interpreted as a percentage number converted by dividing by 100.

- The specification claims screw and joint-compound estimates but provides no formulas, input assumptions, or output definitions for either estimate.

- The specification does not define whether area is gross surface area or net area after subtracting doors, windows, and other openings.

## Units and conventions

- area and sheet_area must use identical square units before division, such as ft² with ft² or m² with m².

- sheet_area is computed as sheet_width × sheet_height.

- waste% is entered as a numeric percentage such as 10 for 10%, so the implemented multiplier is 1 + waste_percent/100.

- The metric test vector converts 500 ft² to 46.45152 m² using 1 ft² = 0.09290304 m².

- The 4×8 and 4×12 sheet sizes are nominal dimensions in feet.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "surface": "walls",
    "area": 480,
    "area_unit": "ft²",
    "sheet_width": 4,
    "sheet_height": 8,
    "sheet_dimension_unit": "ft",
    "waste_percent": 10
  },
  "expected_outputs": {
    "sheets": 17
  },
  "working": "sheet_area = 4 × 8 = 32 ft²\nwaste multiplier = 1 + 10/100 = 1.10\nwaste-adjusted area = 480 × 1.10 = 528 ft²\nraw sheets = 528 ÷ 32 = 16.5\nsheets = ceil(16.5) = 17"
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

A zero sheet dimension produces division by zero and an undefined sheet count. The waste-percent convention also permits a large result discrepancy if the input is interpreted as a fraction instead of a percentage.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/drywall-sheet-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/drywall-sheet-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/drywall-sheet-calculator/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`

- `BOUNDARY_HAZARD_CATALOG.json`