The plan checker's comment is two words long and stops the project cold: second exit. Maybe you are turning the floor above a shop into offices, or adding a third unit over a garage, and the drawing you paid for now needs another staircase that will not fit. Before you redesign anything, it is worth knowing exactly what triggers that second exit — because the answer is a number, and the number is smaller than most people expect.
In California, every story of a building must have at least two separate exits once the occupant load on that story is anywhere from 1 to 500 people; three exits from 501 to 1,000; and four exits above 1,000 (§ 1006.3.3). Homes are the headline exception: Group R-3 and R-4 buildings are allowed a single exit (§ 1006.3.4).
Key numbers
| Occupant load on that story | Minimum exits from that story | Where it says so |
|---|---|---|
| 1–500 | 2 | Table 1006.3.3 |
| 501–1,000 | 3 | Table 1006.3.3 |
| More than 1,000 | 4 | Table 1006.3.3 |
| Houses and duplexes (Group R-3, R-4) | 1 permitted | § 1006.3.4 |
| Apartments (Group R-2), basement through third story | 1 permitted, up to 4 dwelling units and 125 ft travel | Table 1006.3.4(1) |
The word that decides everything is "occupant load"
Occupant load is the code's term for how many people a space is assumed to hold. It is not a headcount of who actually shows up — it is calculated from the use of the space and its floor area, so an empty room still has an occupant load. Everything about exits flows from that one figure: get it wrong and every downstream requirement is wrong with it.
The rule that turns the figure into a requirement is short. All spaces on a story must have access to the required number of separate and distinct exits based on the aggregate occupant load served (§ 1006.3). "Separate and distinct" matters: two doors side by side onto the same corridor are not two exits in any meaningful sense.
Each floor is counted on its own
This is the most commonly misread part of the section, and it usually works in your favor. Where a stairway serves more than one story, only the occupant load of each story considered individually is used to calculate the exits required from that story (§ 1006.3.1).
So a three-story building with 150 people on each floor is not a 450-person problem. It is a 150-person problem, asked three times — and 150 people means two exits per floor, not three. The loads do not stack as they travel down the stair.
When one exit is enough
Single exits are not a loophole; they are written into the code. A story may have a single exit where any one of several conditions is met, and two of them cover most residential work (§ 1006.3.4):
- Group R-3 and R-4 occupancies — the classifications that cover one- and two-family homes and small congregate residences — are permitted a single exit outright. No occupant-load math, no travel-distance test.
- Individual dwelling units in larger buildings may have a single exit from the unit, provided the unit qualifies as a space with one means of egress and either the exit discharges directly outside at ground level, or the corridor outside the unit's front door reaches at least two independent exits.
For apartment buildings as a whole, the allowance is narrower and comes with conditions attached. A Group R-2 story — basement, first, second or third above grade — can be served by one exit with a maximum of 4 dwelling units and a maximum exit access travel distance of 125 feet. The footnotes to that table require the building to be sprinklered throughout and to have emergency escape and rescue openings (Table 1006.3.4(1)). Drop the sprinklers, add a fifth unit, or stretch the walk past 125 feet, and the single-stair scheme is gone.
Rooms inside a floor have their own, tighter rule
The story-level count is only half the picture. Individual rooms, areas and spaces — including mezzanines — get tested separately, and the thresholds there are much lower. Two exits or exit access doorways are required from any space where either the design occupant load or the common path of egress travel distance exceeds the listed values (§ 1006.2.1).
In that table, a Group R-2 space tops out at 20 occupants on one exit, a Group R-3 space at 20, and business, mercantile and educational spaces at 49. "Common path of egress travel" is the stretch you have no choice about — the part of the walk before you reach a point where two different directions of escape open up.
Your escape route cannot wander through the building
One more constraint applies no matter how the count works out:
The path of egress travel to an exit shall not pass through more than one adjacent story.
There are exceptions, and the residential ones are generous: stairs contained within a single dwelling unit in Group R-1, R-2 or R-3 buildings may connect up to four stories, so a three-level townhouse does not violate this. Open parking garages, atriums built to their own section, and exterior stairs between occupiable roofs are also carved out.
The fire code says the same thing
If a fire inspector and a plan checker quote you different section numbers, they are still quoting the same rule. The California Fire Code reproduces these exit-count provisions in its own § 1006, flagged as building-code text. The building code decides what gets drawn and built; the fire code is what keeps those exits clear and usable for as long as the building is occupied.
What these sections do not settle
Be careful about treating an exit count as a finished egress design. The sections above tell you how many exits a story needs — they do not tell you how wide those exits must be, how far apart they must be placed, how far the total travel distance may run to reach one, or how the stair enclosure must be built. Those live in other parts of the means-of-egress chapter that are not quoted here.
The state code is also a floor, not the last word. Cities and counties can and do adopt local amendments to the building and fire codes, so the number your jurisdiction enforces can be stricter than the state's. Before you commit to a single-stair layout, confirm the local amendments with the building department that will actually stamp your plans. These are the 2025 editions, in effect statewide since January 1, 2026.
