Every set of permit drawings for an old building contains a few sheets that look nothing like architecture. They are covered in small numbers: square footages, divisors, and the letters “OCC.” For the Charles S. Pillsbury Mansion, two of those sheets, titled Life Safety Plans, put a number on how many people each floor is drawn to hold.

The sheets, numbered A0.1 and A0.2, belong to a 2025 permit drawing set for the Pillsbury House Renovation at 100 East 22nd Street. They are dated April 18, 2025 and carry a revision marked June 2, 2025, “Plan Review.” This post reads them as a document and nothing more: it is not a statement of how many guests the Pillsbury Club admits, and for visiting details the place to look is the Club’s plan your visit page.

How do you read “SF / 15 = 21 OCC” on a life safety plan?

Each room on the sheets carries a small calculation: the room’s area in square feet, divided by a number that depends on how the space is used, equals its occupant load. A card room of 307 square feet marked “307 SF / 15 = 21 OCC” is being counted at one person per 15 square feet. A shop of 878 square feet marked “/ 100” is counted far more loosely, at nine. The more crowded a use is expected to be, the smaller the divisor, and the larger the load.

What does each floor of the Pillsbury Mansion add up to on the plan?

The sheets print a total in the title of each floor plan:

• Basement: 55 OCC. The room-by-room lines include the card room (21), a rec room of 431 square feet (29), a shop (9) and a storage room of 590 square feet (2). The sheet also marks the boiler room, the stair hall lobby, a fire alarm control panel room and a gas shutoff.
• First floor: 77 OCC. The largest line is the dining room, labeled Assembly A2: 840 square feet divided by 15 gives 56. The kitchen is counted at 3, and two rooms labeled retail at 12 and 4. The conservatory, main hall, vestibule and restrooms are also drawn on the sheet.
• Second floor: 5,346 SF, 16 OCC, “4 resident suites.” The suite lines are counted at one person per 200 square feet: 3 for a 600-square-foot suite, 5 for one of 1,038 square feet, 4 for an accessible suite of 838, and 2 for a single room of 391.
• Third floor: 4,845 SF, 12 OCC, “1 resident suite.” One suite of 663 square feet is counted at 4, and an office suite of 1,215 square feet at 8. Separately, the third-floor hall is labeled Assembly: 705 square feet divided by 15, or 47. That figure is printed on the sheet next to the floor total of 12, and the drawing does not explain how the two relate, so we report both as printed.

Adding the four printed floor totals gives 160, but the sheets do not present that as a building total, and we are not claiming one. The labels “resident suite” and “retail” are classifications on a permit drawing, not a description of what is offered to the public today.

What are the exit separations and smoke curtains?

Life safety plans are really about getting out. Each floor shows an arrow-and-label key for exits, exit signs, emergency lights and fire extinguisher cabinets, plus a wall key distinguishing half-hour partitions and demising walls from two-hour shaft walls. The stairs are marked “smoke limiting,” and smoke curtains are drawn near the elevator lobbies.

The drawings also dimension how far apart the exits are. A long diagonal across the house, 105 feet 7 inches on the basement, first and second floors, is the yardstick, with shorter “exit separation” dimensions marked on each floor: 57 feet 5 inches in the basement, 50 feet 4 inches on the first floor, 44 feet on the second and 41 feet 4 inches on the third. These are the numbers a reviewer checks against the code. For background on how the National Park Service thinks about applying building codes to historic buildings, see its Preservation Briefs, which include Brief 51 on building codes and Brief 32 on accessibility.

What do the two keynotes on the sheet ask for?

Two keynotes appear in the key on the upper-floor sheets. One calls for a sign reading “Accessible restrooms are located on first floor.” The other says to install a fall guard at an existing window. Several upper-floor rooms are also tagged as accessible or as hearing- and vision-impaired accessible.

Where this fits in the mansion’s paper trail

These sheets are one more layer in a stack of documents we have been reading, from the October 2024 feasibility drawings to the preservation architect’s floor-by-floor survey and the story of fitting sprinklers into a 1916 mansion. Together they show how a National Register house is rewritten, a floor at a time, to meet twenty-first-century rules without losing the oak and plaster that make it worth visiting.

Want to see how it all works in person? Plan a visit through the Pillsbury Club’s plan your visit page, or browse the History Journal for more of the mansion’s story.

Keep reading: What Does an Architect’s Window Detail Sheet Say About the Pillsbury Mansion’s Steel Sash and Stained Glass Medallions?