Occupancy Calculator

What it does

Type /occupancy-calculator in Claude Code and describe your building. The skill turns Claude into a code consultant that calculates the maximum occupant load for any building or space using IBC Table 1004.5 — the table that drives egress, plumbing fixtures, and ventilation requirements.

Every calculation shows the math: use type classification, gross vs net area, load factor, and resulting occupant count per area.

Install

Claude Desktop:

1. Open Customize → Browse plugins
2. Click + → Add marketplace from GitHub
3. Enter AlpacaLabsLLC/skills-for-architects
4. Install the Programming plugin

Claude Code (terminal):

claude install github:AlpacaLabsLLC/skills-for-architects/03-programming

Usage

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

Or describe a mixed-use building:

/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 /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.