# International Building Code (IBC) - General Requirements

**Edition**: IBC 2021 (basis for most current state codes)
**Publisher**: International Code Council (ICC)

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## Occupancy Classifications (Chapter 3)

### Assembly (A)
| Group | Description | Examples |
|-------|-------------|----------|
| A-1 | Fixed seating, performing arts | Theaters, concert halls |
| A-2 | Food/drink consumption | Restaurants, bars, nightclubs |
| A-3 | Worship, recreation, amusement | Churches, gyms, museums |
| A-4 | Indoor viewing of sports | Arenas, skating rinks |
| A-5 | Outdoor activities | Stadiums, grandstands |

### Business (B)
- Offices, banks, educational above 12th grade
- Professional services, outpatient clinics

### Educational (E)
- K-12 educational facilities
- Day care for 6+ children (> 2.5 years old)

### Factory (F)
| Group | Description |
|-------|-------------|
| F-1 | Moderate hazard (furniture, auto repair) |
| F-2 | Low hazard (electronics, food processing) |

### High Hazard (H)
| Group | Description |
|-------|-------------|
| H-1 | Detonation hazard |
| H-2 | Deflagration hazard, accelerated burning |
| H-3 | Readily combustible materials |
| H-4 | Health hazards |
| H-5 | Semiconductor fabrication (HPM) |

### Institutional (I)
| Group | Description |
|-------|-------------|
| I-1 | 16+ persons, supervised residential (assisted living) |
| I-2 | Medical/nursing care, 24-hour (hospitals, nursing homes) |
| I-3 | Restrained occupants (jails, prisons) |
| I-4 | Day care (5+ children under 2.5, or 6+ children any age) |

### Mercantile (M)
- Retail stores, markets, sales rooms
- Motor fuel dispensing

### Residential (R)
| Group | Description |
|-------|-------------|
| R-1 | Transient (hotels, motels, boarding houses) |
| R-2 | Permanent (apartments, dormitories, condos) |
| R-3 | 1-2 family dwellings, adult/child care ≤ 5 |
| R-4 | Residential care/assisted living (5-16 persons) |

### Storage (S)
| Group | Description |
|-------|-------------|
| S-1 | Moderate hazard (furniture, tires, lumber) |
| S-2 | Low hazard (glass, metal, food in noncombustible containers) |

### Utility (U)
- Agricultural buildings, carports, greenhouses, sheds

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## Construction Types (Chapter 6)

### Type I - Noncombustible
| Subtype | Structural Frame | Bearing Walls | Floor/Roof |
|---------|------------------|---------------|------------|
| I-A | 3 hour | 3 hour | 2 hour / 1.5 hour |
| I-B | 2 hour | 2 hour | 2 hour / 1 hour |

### Type II - Noncombustible
| Subtype | Structural Frame | Bearing Walls | Floor/Roof |
|---------|------------------|---------------|------------|
| II-A | 1 hour | 1 hour | 1 hour / 1 hour |
| II-B | 0 hour | 0 hour | 0 hour / 0 hour |

### Type III - Exterior Noncombustible
| Subtype | Structural Frame | Bearing Walls (Ext) | Bearing Walls (Int) |
|---------|------------------|---------------------|---------------------|
| III-A | 1 hour | 2 hour | 1 hour |
| III-B | 0 hour | 2 hour | 0 hour |

### Type IV - Heavy Timber
- Mass timber or heavy timber interior
- 2-hour exterior walls
- Specific member sizes required

### Type V - Combustible
| Subtype | Structural Frame | Bearing Walls | Floor/Roof |
|---------|------------------|---------------|------------|
| V-A | 1 hour | 1 hour | 1 hour / 1 hour |
| V-B | 0 hour | 0 hour | 0 hour / 0 hour |

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## Allowable Building Height and Area (Chapter 5)

### Table 504.3 - Allowable Building Height (Feet)

| Occupancy | I-A | I-B | II-A | II-B | III-A | III-B | IV | V-A | V-B |
|-----------|-----|-----|------|------|-------|-------|-----|-----|-----|
| A-1 | UL | 160 | 65 | 55 | 65 | 55 | 65 | 50 | 40 |
| A-2 | UL | 160 | 65 | 55 | 65 | 55 | 65 | 50 | 40 |
| B | UL | 180 | 65 | 55 | 65 | 55 | 65 | 50 | 40 |
| E | UL | 160 | 65 | 55 | 65 | 55 | 65 | 50 | 40 |
| M | UL | 180 | 65 | 55 | 65 | 55 | 65 | 50 | 40 |
| R-1 | UL | 180 | 65 | 55 | 65 | 55 | 65 | 50 | 40 |
| R-2 | UL | 180 | 65 | 55 | 65 | 55 | 65 | 50 | 40 |

UL = Unlimited

### Table 504.4 - Allowable Building Height (Stories)

| Occupancy | I-A | I-B | II-A | II-B | III-A | III-B | IV | V-A | V-B |
|-----------|-----|-----|------|------|-------|-------|-----|-----|-----|
| A-1 | UL | 5 | 3 | 2 | 3 | 2 | 3 | 2 | 1 |
| A-2 | UL | 11 | 3 | 2 | 3 | 2 | 3 | 2 | 1 |
| B | UL | 11 | 5 | 3 | 5 | 3 | 5 | 3 | 2 |
| E | UL | 5 | 3 | 2 | 3 | 2 | 3 | 2 | 1 |
| M | UL | 11 | 4 | 2 | 4 | 2 | 4 | 3 | 1 |
| R-1 | UL | 11 | 4 | 4 | 4 | 4 | 4 | 3 | 2 |
| R-2 | UL | 11 | 4 | 4 | 4 | 4 | 4 | 3 | 2 |

### Table 506.2 - Allowable Area (Square Feet Per Floor)

| Occupancy | I-A | I-B | II-A | II-B | III-A | III-B | IV | V-A | V-B |
|-----------|-----|-----|------|------|-------|-------|-----|-----|-----|
| A-1 | UL | UL | 15,500 | 8,500 | 14,000 | 8,500 | 15,000 | 11,500 | 5,500 |
| A-2 | UL | UL | 15,500 | 9,500 | 14,000 | 9,500 | 15,000 | 11,500 | 6,000 |
| B | UL | UL | 37,500 | 23,000 | 28,500 | 19,000 | 36,000 | 18,000 | 9,000 |
| E | UL | UL | 26,500 | 14,500 | 23,500 | 14,500 | 25,500 | 18,500 | 9,500 |
| M | UL | UL | 21,500 | 12,500 | 18,500 | 12,500 | 20,500 | 14,000 | 9,000 |
| R-1 | UL | UL | 24,000 | 16,000 | 24,000 | 16,000 | 20,500 | 12,000 | 7,000 |
| R-2 | UL | UL | 24,000 | 16,000 | 24,000 | 16,000 | 20,500 | 12,000 | 7,000 |

### Area Increases

**Frontage Increase (507.2)**:
```
If = 100 × (F/P - 0.25) × W/30

Where:
F = Building perimeter fronting on open space
P = Total building perimeter
W = Width of open space (20' min, 30' max)
```

**Sprinkler Increase (506.3)**:
- Multi-story: 200% increase (3× base area)
- Single-story: 300% increase (4× base area)
- Unlimited area: Available for certain combinations

---

## Fire-Resistance Ratings (Chapter 7)

### Table 601 - Fire-Resistance Requirements (Hours)

| Building Element | I-A | I-B | II-A | II-B | III-A | III-B | IV | V-A | V-B |
|------------------|-----|-----|------|------|-------|-------|-----|-----|-----|
| Primary structural frame | 3 | 2 | 1 | 0 | 1 | 0 | HT | 1 | 0 |
| Bearing walls - Exterior | 3 | 2 | 1 | 0 | 2 | 2 | 2 | 1 | 0 |
| Bearing walls - Interior | 3 | 2 | 1 | 0 | 1 | 0 | 1/HT | 1 | 0 |
| Nonbearing walls (Ext) | Note a | Note a | Note a | Note a | Note a | Note a | Note a | Note a | Note a |
| Floor construction | 2 | 2 | 1 | 0 | 1 | 0 | HT | 1 | 0 |
| Roof construction | 1.5 | 1 | 1 | 0 | 1 | 0 | HT | 1 | 0 |

HT = Heavy Timber
Note a: Per Table 602 based on fire separation distance

### Table 602 - Fire-Resistance Based on Separation Distance

| Fire Separation Distance | Group H | Group F-1, M, S-1 | Others |
|--------------------------|---------|-------------------|--------|
| < 5 feet | 3 hour | 2 hour | 1 hour |
| 5 - < 10 feet | 2 hour | 1 hour | 1 hour |
| 10 - < 30 feet | 1 hour | 1 hour | 0 hour |
| ≥ 30 feet | 0 hour | 0 hour | 0 hour |

---

## Fire Barriers, Walls, and Partitions (Chapter 7)

### Fire Walls (706)
- **Rating**: 2-4 hours (per Table 706.4)
- **Purpose**: Divide building into separate structures
- **Structural stability**: Must remain standing if structure on one side collapses

### Fire Barriers (707)
- **Purpose**: Separate occupancies, exit enclosures, shafts
- **Ratings**: Per specific use

| Use | Rating |
|-----|--------|
| Shaft enclosure (4+ stories) | 2 hour |
| Shaft enclosure (< 4 stories) | 1 hour |
| Exit enclosure (4+ stories) | 2 hour |
| Exit enclosure (< 4 stories) | 1 hour |
| Exit passageway | Same as exit enclosure |
| Horizontal exit | 2 hour |
| Incidental use separation | Per Table 509 |
| Occupancy separation | Per Table 508.4 |

### Fire Partitions (708)
- **Rating**: 1 hour (or less per specific use)
- **Use**: Dwelling/sleeping unit separation, corridor walls

### Smoke Barriers (709)
- **Rating**: 1 hour
- **Continuous**: Floor to underside of floor/roof above

### Smoke Partitions (710)
- **Rating**: Not required (smoke-tight only)
- **Use**: I-2 corridor walls, elevator lobbies

---

## Mixed Occupancy (508)

### Separated Uses
- Each occupancy must meet its own requirements
- Fire barrier between occupancies per Table 508.4

### Non-Separated Uses
- Building treated as most restrictive occupancy for:
  - Height
  - Area
  - Construction type
  - Fire protection

### Accessory Occupancies
- Max 10% of floor area
- Aggregate max 10% of building
- No separation required (except H, I-1, I-2)

### Table 508.4 - Required Separation (Hours)

| | A | B | E | F-1 | F-2 | H-1 | H-2 | I-1 | I-2 | M | R | S-1 | S-2 |
|---|---|---|---|-----|-----|-----|-----|-----|-----|---|---|-----|-----|
| A | - | - | - | 1 | - | NP | 2 | 2 | 2 | - | - | 1 | - |
| B | - | - | - | 1 | - | NP | 2 | 2 | 2 | - | - | 1 | - |
| E | - | - | - | 1 | - | NP | 2 | 2 | 2 | - | - | 1 | - |
| R | - | - | - | 1 | - | NP | 2 | 2 | 2 | - | - | 1 | - |
| I-2 | 2 | 2 | 2 | 2 | 2 | NP | NP | 2 | - | 2 | 2 | 2 | 2 |

NP = Not Permitted
S = Sprinklered (may reduce by 1 hour)

---

## Plumbing Fixture Requirements (Chapter 29)

### Table 2902.1 - Minimum Facilities

| Occupancy | Water Closets | Lavatories | Bathtub/Shower | Drinking Fountain |
|-----------|---------------|------------|----------------|-------------------|
| Assembly | 1/125 (M), 1/65 (W) | 1/200 | - | 1/500 |
| Business | 1/25 (M&W first 50), 1/50 thereafter | 1/40 | - | 1/100 |
| Educational | 1/50 | 1/50 | - | 1/100 |
| Mercantile | 1/500 (M&W) | 1/750 | - | 1/1000 |
| Residential | 1/dwelling | 1/dwelling | 1/dwelling | - |
| Institutional | Per specific code | Per specific code | Per specific code | 1/100 |

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## Special Detailed Requirements (Chapter 4)

### High-Rise Buildings (403)
**Applies when**: Building floor > 75' above fire department access

**Required**:
- Automatic sprinklers throughout
- Fire alarm and detection
- Emergency voice/alarm communication
- Fire command center
- Central control station
- Smokeproof enclosures OR pressurized exit stairs
- Fire service access elevators
- Standby power and emergency power
- Luminous egress path markings (75'-420' above grade)

### Atriums (404)
**Required**:
- Automatic sprinklers
- Smoke control system
- Fire barriers at atrium openings (or alternative)
- Standby power for smoke control

### Underground Buildings (405)
**Applies when**: Lowest occupied floor > 30' below exit discharge

**Required**:
- Automatic sprinklers
- Standby power
- Smoke control
- Compartmentalization

### Covered/Open Mall Buildings (402)
- Anchor building separation
- Tenant separation
- Exit requirements
- Automatic sprinklers

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## General Building Limitations Summary

### Quick Reference - What Can I Build?

**Unlimited Height/Area** (Type I-A):
- Any occupancy
- No sprinkler increase needed
- High-rise requirements apply above 75'

**Common Wood Construction** (Type V-B):
- Max 40' height
- 1-2 stories (varies by occupancy)
- Base area ~9,000 SF (can triple with sprinklers)

**Typical Multi-Family** (Type V-A):
- 3 stories, 50' height
- 12,000 SF per floor
- Can reach 4 stories/36,000 SF with sprinklers

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## Code Update Cycle

| Edition | Based On | Typical Adoption |
|---------|----------|------------------|
| IBC 2024 | Current | 2025-2027 |
| IBC 2021 | Current | 2022-2024 |
| IBC 2018 | Legacy | 2019-2021 |
| IBC 2015 | Legacy | 2016-2018 |

*Always verify adopted edition with local AHJ*

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*Reference: International Building Code 2021, ICC*
*State and local amendments may modify these requirements*
