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Skill Claude Desktop · Claude Code

# /occupancy-calculator

IBC occupancy load calculator for Claude Code

[Install ↓](#install) [View on GitHub →](https://github.com/AlpacaLabsLLC/skills-for-architects/tree/main/skills/occupancy-calculator) [New to skills? →](/articles/claude-code-cheat-sheet) [All skills →](/skills)

[Programming](/skills?tag=programming) [Analysis](/skills?tag=analysis)

## What it does

Type `/as:occupancy-calculator` in Claude Code and describe your building. The skill asks what state or city your project is in, loads the correct code table, and calculates the maximum occupant load — the number that drives egress, plumbing fixtures, and ventilation requirements.

**Jurisdiction-aware.** NYC projects use the [NYC Building Code 2022](https://codelibrary.amlegal.com/codes/newyorkcity/latest/NYCbldg/). California projects use the [CBC 2022](https://govt.westlaw.com/calregs/). Other US states use IBC 2021 as a reference with a link to verify at [UpCodes](https://up.codes/viewer/general/ibc-2021/chapter/10).

Every calculation shows the math: use type classification, gross vs net area, load factor, resulting occupant count, and a link to the public code source used.

## Install

**Claude Desktop:**

1.  Open **Customize** → **Browse plugins**
2.  Click **+** → **Add marketplace from GitHub**
3.  Enter `AlpacaLabsLLC/skills-for-architects`
4.  Install **Architecture Studio**

**Claude Code (terminal):**

```
claude plugin marketplace add AlpacaLabsLLC/skills-for-architects
claude plugin install as@skills-for-architects
```

Or symlink just this skill:

```
git clone https://github.com/AlpacaLabsLLC/skills-for-architects.git
ln -s $(pwd)/skills-for-architects/skills/occupancy-calculator ~/.claude/skills/occupancy-calculator
```

## Usage

```
/as:occupancy-calculator 50,000 SF office building, 3 floors
```

Or describe a mixed-use building:

```
/as:occupancy-calculator ground floor retail (8,000 SF) + 4 floors office (40,000 SF)
```

The skill works through four phases:

-   **Discover** — Learns about your building and identifies use types
-   **Calculate** — Assigns IBC load factors and calculates occupant loads per area
-   **Detail** — Provides egress requirements derived from the occupant load
-   **Refine** — Handles adjustments with before/after comparison

## Demo: Mixed-Use Office Building — 50,000 SF

Real output from a session. The brief: “50K SF office, 3 floors, ground floor has a 2,000 SF café and 500 SF lobby.”

The skill classified each area independently and flagged that the café — only 4% of floor area — drives 30% of the building’s occupant load:

Area

Use Type

SF

Gross/Net

Load Factor

Occupants

Office (Floors 1-3)

Business Areas

44,000

Gross

150

294

Ground Floor Café

Assembly — Unconcentrated

2,000

Net

15

134

Café Kitchen

Kitchens — Commercial

1,500

Gross

200

8

Lobby

Business Areas

500

Gross

150

4

Storage/Mechanical

Accessory Storage

2,000

Gross

300

7

**Total**

**50,000**

**447**

**447 total occupants** requires 3 exits (>250), 90” minimum stair width, and 67” minimum corridor width.

## Workplace Programmer Integration

If a `program.json` file exists in the working directory (from `/as:workplace-programmer`), the skill offers to calculate occupancy directly from the room schedule — mapping conference rooms to assembly, open desks to business, kitchens to commercial kitchen, and storage to accessory. The code occupant load is almost always higher than actual headcount.

## What’s included

-   **39 use types** — IBC 2021 Table 1004.5 occupancy load factors with gross/net designation, aliases for fuzzy matching, and NYC Building Code variant notes
-   **21 use groups** — IBC use group classifications (A-1 through U) with descriptions and examples

## Customization

Everything the skill knows lives in editable JSON — no code to change.

### Add use types

Your project has a use type not in the defaults? Add it to `data/occupancy-load-factors.json` with an ID, use group, load factor, gross/net designation, and aliases for fuzzy matching.

```
{
  "id": "data-center",
  "use": "Data Center — Server Floor",
  "use_group": "B",
  "load_factor_sf": 300,
  "area_type": "gross",
  "ibc_table": "1004.5",
  "code_edition": "IBC 2021",
  "aliases": ["server room", "data hall", "colocation"],
  "notes": "Not explicitly listed in IBC — classified as accessory or business depending on jurisdiction."
}
```

### Add jurisdiction variants

Working under the NYC Building Code or another local amendment? The `notes` field on each use type documents jurisdiction-specific differences. The skill reads and cites these during calculations.

### Change the persona

Edit `SKILL.md` to swap “code consultant” for “fire marshal” or “plan reviewer” — the conversation flow adapts to whatever role you write in.

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[← All skills](/skills) [Workplace Programmer →](/skills/workplace-programmer)