CMC · California Mechanical Code
What access and platform requirements apply to rooftop appliances?
Homeowner summary: The California Mechanical Code requires rooftop equipment be reachable and serviceable — keep 30 inches of working space, use 30×30-inch platforms on steep roofs, stay 6 feet from roof edges or add 42-inch guards, and for buildings taller than 15 feet provide inside access (scuttle or ladder) so technicians can safely reach rooftop appliances (see §§ 303.8 and 304.3).
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Rooftop appliances must be both located and installed so they can be safely serviced — that includes minimum working clearances, platforms/walkways where required, edge protections when the appliance is close to a roof edge, and durable access from the building where the building exceeds a height threshold. The controlling rules are § 303.8 (Appliances on roofs) and § 304.3 (Access to appliances on roofs) of the California Mechanical Code.
The single most important rule: rooftop equipment must be installed and positioned so it can be safely accessed and serviced — if the roof or layout prevents safe access, provide platforms, walkways, rails, or interior access as required by the code.
Requirements in detail
General accessibility and working clearances
- Maintain a minimum working space of 30 inches (762 mm) in depth, width, and height around appliances unless another dimension is specifically required. § 304.1.
- All rooftop appliances must be accessible (not blocked by permanent construction). § 304.3.
Platforms, walkways, and sloped roofs
- Where roof design causes ponding or a water seal, provide a raised platform or walkway above the waterline adjacent to appliances and their control panels so the unit can be safely serviced. § 303.8.6.
- On roofs with a slope of 4 in 12 (33%) or greater, provide a level platform of at least 30 inches by 30 inches (762 mm × 762 mm) at the service side of equipment. § 304.2.
Roof-edge clearance and guards
- Appliances must be installed on a well-drained surface and have at least 6 feet (1829 mm) clearance from any part of the appliance to the roof edge or provide fixed guards/rails. § 303.8.4.
- Where guards/rails are required, they must be a minimum 42 inches (1067 mm) in height, be constructed to resist loads, prevent the passage of a 21‑inch (533 mm) diameter ball, and extend not less than 30 inches (762 mm) beyond each side of the equipment. § 303.8.4.1.
- Exception: guards are not required if a permanent fall arrest anchorage connector system per ASSP Z359.1 is installed. § 303.8.4.1 (Exception).
Access from inside the building and access openings
- Buildings taller than 15 feet (4572 mm) must provide an inside means of access to the roof (permanent or foldaway stairway/ladder terminating in an enclosure, scuttle, or trapdoor) unless the AHJ accepts another means. § 304.3.1.
- Scuttles/trapdoors must be at least 22 inches by 24 inches (559 mm × 610 mm), open easily (including under snow), and permit access from the roof side unless intentionally locked. § 304.3.1.1.
- Provide permanent lighting at roof access with the switch located inside the building near the access means. § 304.3.2.
Permanent ladders — construction requirements
When a permanent ladder is used for inside access it must meet these minimums (see § 304.3.1.2):
- Side railings extend at least 30 inches (762 mm) above the roof or parapet.
- Landings not more than 18 feet (5486 mm) apart.
- Width not less than 14 inches (356 mm) on center.
- Rung spacing not more than 12 inches (305 mm) on center; each rung must support 300 pounds (136.1 kg).
- Toe space not less than 6 inches (152 mm).
Roof structure and attachment considerations
- Roofs must be capable of supporting the additional load of rooftop appliances or be reinforced. § 303.8.1.
- Access hardware (locks, screws, bolts) must be corrosion-resistant. § 303.8.2.
Table — Decision-relevant dimensions / values
| Decision factor | Required value (U.S./metric) | Code Reference |
|---|---|---|
| Minimum working space around appliance | 30 in (762 mm) depth/width/height | § 304.1 |
| Platform for sloped roof (≥4:12) | 30 in × 30 in (762 × 762 mm) level platform | § 304.2 |
| Scuttle/trapdoor minimum size | 22 in × 24 in (559 × 610 mm) | § 304.3.1.1 |
| Building height threshold for inside access | 15 ft (4572 mm) | § 304.3.1 |
| Clearance to roof edge (or else guards) | 6 ft (1829 mm) | § 303.8.4 |
| Guard/rail minimum height | 42 in (1067 mm) | § 303.8.4.1 |
| Guard must prevent ball passage | 21 in (533 mm) diameter ball | § 303.8.4.1 |
| Guard extension beyond equipment | 30 in (762 mm) each side | § 303.8.4.1 |
| Ladder side rail extension above roof | 30 in (762 mm) | § 304.3.1.2 (1) |
| Ladder rung spacing | ≤ 12 in (305 mm) | § 304.3.1.2 (4) |
| Ladder rung load capacity | 300 lb (136.1 kg) | § 304.3.1.2 (4) |
| Ladder width minimum | 14 in (356 mm) | § 304.3.1.2 (3) |
| Ladder landing spacing max | 18 ft (5486 mm) | § 304.3.1.2 (2) |
| Toe space on ladder | 6 in (152 mm) | § 304.3.1.2 (5) |
Exceptions & special cases
- No platform required for unit heaters or room heaters (exception in § 304.1).
- No guards required where a permanent fall arrest anchorage connector system in accordance with ASSP Z359.1 is installed (exception to § 303.8.4.1).
- A working platform in front of a furnace need not be provided if the furnace is serviceable from the required access opening and the service side is within 12 inches (305 mm) of that opening (exception to § 304.4.3).
If your rooftop appliance is within a special occupancy (for example, specific provisions for refrigeration machinery, PV rooftop platforms, or rooftop evacuation locations), consult the related chapters and the Authority Having Jurisdiction — those topics are addressed elsewhere in the code and related California codes. Some of those related provisions are shown in the code library but are outside § 303.8 and § 304.3.
Common mistakes
- Assuming any narrow path to the unit counts as service access — the code requires 30 in working space unless a specific alternate dimension is given. § 304.1.
- Forgetting to account for roof slope — sloped roofs ≥ 4:12 trigger a 30×30 in platform requirement at the service side. § 304.2.
- Placing an appliance less than 6 ft from the roof edge without providing required 42 in guards and the required guard extensions. § 303.8.4 / 303.8.4.1.
- Omitting permanent lighting at roof access. § 304.3.2.
- Relying on rooftop surface strength without verifying the roof can support the appliance load — § 303.8.1 requires structural capacity or reinforcement.
Worked example — concrete scenario
Scenario: You are installing a gas rooftop condensing unit on a commercial building. The roof slope is 5 in 12, the roof edge is 4 feet from the unit's service panel, and the building is 24 feet tall.
Step-by-step application:
- Roof slope 5:12 (which is ≥ 4:12) — provide a level platform at the service side of at least 30 in × 30 in so technicians can safely service the unit. § 304.2.
- Unit is 4 ft from the roof edge (< 6 ft), so you must provide rigidly fixed guards/rails a minimum 42 in high that prevent passage of a 21 in diameter ball, extend 30 in beyond each side of the unit, and resist imposed loads. § 303.8.4 / 303.8.4.1.
- Building height 24 ft (> 15 ft) — provide an inside means of access to the roof (a permanent or foldaway stairway or ladder terminating in a scuttle/trapdoor). § 304.3.1.
- If you choose a permanent ladder, size it per § 304.3.1.2 (rungs ≤ 12 in apart, width ≥ 14 in, side rails extend 30 in above roof, rungs rated 300 lb, landings ≤ 18 ft).
- If the rooftop tends to pond water around the unit, add a platform or walkway above the waterline adjacent to the unit and control panels so servicing is safe. § 303.8.6.
- Confirm the roof can support the unit weight or reinforce per § 303.8.1.
Related provisions
- § 303.8 — Appliances on roofs (general requirements, guard, platform, load).
- § 303.8.1 — Roof load capacity for appliances.
- § 303.8.4 / § 303.8.4.1 — Edge clearance; guards and rails.
- § 303.8.6 — Platform or walkway where water stands on roof.
- § 304.1 — General accessibility and minimum clearances (30 in).
- § 304.2 — Platform requirement for steep/sloped roofs (30×30 in).
- § 304.3 — Appliances on roofs must be accessible.
- § 304.3.1 / § 304.3.1.1 / § 304.3.1.2 — Inside means of access, scuttle dimensions, and permanent ladder specs.
- § 304.3.2 — Permanent lighting at roof access.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 303.8 High relevance — show source text
303.8 Appliances on Roofs. Appliances on roofs shall be designed or enclosed so as to withstand climatic conditions in the area in which they are installed. Where enclosures are provided, each enclosure shall permit easy entry and movement, shall be of reasonable height, and shall have at least a 30 inch (762 mm) clearance between the entire service access panel(s) of the appliance and the wall of the enclosure. [NFPA 54:9.4.1.1]
303.8.1 Load Capacity. Roofs on which appliances are to be installed shall be capable of supporting the additional load or shall be reinforced to support the additional load. [NFPA 54:9.4.1.2]
303.8.2 Fasteners. All access locks, screws, and bolts shall be of corrosion-resistant material. [NFPA 54:9.4.1.3]
303.8.3 Installation of Appliances on Roofs. Appliances shall be installed in accordance with the manufacturer’s installation instructions. [NFPA 54:9.4.2.1]
303.8.4 Edge of Roof Clearance. Appliances shall be installed on a well-drained surface of the roof. At least 6 feet (1829 mm) of clearance shall be available between any part of the appliance and the edge of a roof or similar hazard, or rigidly fixed rails, guards, parapets, or other building structures at least 42 inches (1067 mm) in height shall be provided on the exposed side. [NFPA 54:9.4.2.2]
303.8.4.1 Guards and Rails. Guards or rails shall be required where the following exist:
(1) The clearance between the appliance and a roof edge or open end of an equipment platform is less than 6 feet (1829 mm).
(2) The open end of the equipment platform is located more than 30 inches (762 mm) above the roof, floor, or grade below.
Where guards or rails are installed, they shall be constructed so as to prevent the passage of a 21 inch (533 mm) diameter ball, resist the imposed loading conditions, and shall extend not less than 30 inches (762 mm) beyond each side of the equipment or appliance.
Exception: Guards shall not be required where a permanent fall arrest anchorage connector system in accordance with ASSP Z359.1 is installed.
303.8.5 Electrical Power. Appliances requiring an external source of electrical power shall be installed in accordance with the California Electrical Code . [NFPA 54:9.4.2.3]
303.8.6 Platform or Walkway. Where water stands on the roof at the appliance or in the passageways to the appliance, or where the roof is of a design having a water seal, a suitable platform, walkway, or both shall be provided above the water line. Such platform(s) or walkway(s) shall be located adjacent to the appliance and control panels so that the appliance can be safely serviced where water stands on the roof. [NFPA 54:9.4.2.4] 303.9 Avoiding Strain on Gas Piping. Appliances shall be supported and connected to the piping so as not to exert undue strain on the connections. [NFPA 54:9.1.16] **303.10 Clearance to Combustible Materials.
CMC § 304.0 High relevance — show source text
304.0 Accessibility for Service. 304.1 General. All appliances shall be located with respect to building construction and other equipment so as to permit access for repair or replacement of the appliance. Clearance shall be maintained to permit removal of the appliance; cleaning of heating surfaces; the replacement of filters, blowers, motors, burners, controls, and vent connections; the lubrication of moving parts where necessary; the adjustment and cleaning of burners and pilots; and the proper functioning of explosion vents, if provided. For attic installation, the passageway and servicing area adjacent to the appliance shall be in accordance with Section 304.4. {NFPA 54:9.2.1}
Unless otherwise specified, clearances of not less than 30 inches (762 mm) in depth, width, and height of working space shall be maintained.
Exception: A platform shall not be required for unit heaters or room heaters.
304.2 Sloped Roof. Where equipment or appliances that require service are installed on a roof having a slope of 4 units vertical in 12 units horizontal (33 percent slope) or more, a level platform of not less than 30 inches by 30 inches (762 mm by 762 mm) shall be provided at the service side of the equipment or appliance. 304.3 Access to Appliances on Roofs. Appliances located on roofs or other elevated locations shall be accessible. [NFPA 54:9.4.3.1]
304.3.1 Access from the Inside. Buildings of more than 15 feet (4572 mm) in height shall have an inside means of access to the roof unless other means acceptable to the Authority Having Jurisdiction are used. [NFPA 54:9.4.3.2]
304.3.1.1 Access Type. The inside means of access shall be a permanent or foldaway inside stairway or ladder, terminating in an enclosure, scuttle, or trapdoor. Such scuttles or trapdoors shall be at least 22 inches by 24 inches (559 mm by 610 mm) in size, shall open easily and safely under all conditions, especially snow, and shall be constructed so as to permit access from the roof side unless deliberately locked on the inside.
At least 6 feet (1829 mm) of clearance shall be available between the access opening and the edge of the roof or similar hazard, or rigidly fixed rails or guards a minimum of 42 inches (1067 mm) in height shall be provided on the exposed side. Where parapets or other building structures are utilized in lieu of guards or rails, they shall be a minimum of 42 inches (1067 mm) in height. [NFPA 54:9.4.3.3]
304.3.1.2 Permanent Ladders. Permanent lad ders required by Section 304.3.1.1 shall be constructed in accordance with the following:
(1) Side railings shall extend not less than 30 inches (762 mm) above the roof or parapet wall.
(2) Landings shall not exceed 18 feet (5486 mm) apart measured from the finished grade.
(3) Width shall be not less than 14 inches (356 mm)
on center.
(4) Rungs spacing shall not exceed 12 inches (305 mm) on center, and each rung shall be capable of supporting a 300 pound (136.1 kg) load.
(5) Toe space shall be not less than 6 inches (152 mm).
CMC § 303.8.5 High relevance — show source text
(1) The clearance between the appliance and a roof edge or open end of an equipment platform is less than 6 feet (1829 mm).
(2) The open end of the equipment platform is located more than 30 inches (762 mm) above the roof, floor, or grade below.
Where guards or rails are installed, they shall be constructed so as to prevent the passage of a 21 inch (533 mm) diameter ball, resist the imposed loading conditions, and shall extend not less than 30 inches (762 mm) beyond each side of the equipment or appliance.
Exception: Guards shall not be required where a permanent fall arrest anchorage connector system in accordance with ASSP Z359.1 is installed.
303.8.5 Electrical Power. Appliances requiring an external source of electrical power shall be installed in accordance with the California Electrical Code . [NFPA 54:9.4.2.3]
303.8.6 Platform or Walkway. Where water stands on the roof at the appliance or in the passageways to the appliance, or where the roof is of a design having a water seal, a suitable platform, walkway, or both shall be provided above the water line. Such platform(s) or walkway(s) shall be located adjacent to the appliance and control panels so that the appliance can be safely serviced where water stands on the roof. [NFPA 54:9.4.2.4] 303.9 Avoiding Strain on Gas Piping. Appliances shall be supported and connected to the piping so as not to exert undue strain on the connections. [NFPA 54:9.1.16] 303.10 Clearance to Combustible Materials. Appliances and their vent connectors shall be installed with clearances from combustible material so their operation does not create a hazard to persons or property. Minimum clearances between combustible walls and the back and sides of various conventional types of appliances and their vent connectors are specified in Chapter 8 and Chapter 9, or NFPA 211.
[NFPA 54:9.2.2] Where not provided in this code, listed and unlisted equipment or appliances shall be installed to maintain the required clearances for servicing and to combustible construction in accordance with the listing and the manufacturer’s installation instructions.
303.10.1 Clearance Reduction. Reduced clearances to combustible construction for listed equipment and appliances shall comply with the listing and Table 303.10.1. Where permitted by the manufacturer, and not provided in this code, reduced clearances to combustible construction for unlisted equipment and appliances shall comply with Table 303.10.1. 303.10.1.1 Type I Hood Exhaust System. Reduced clearances for Type I exhaust systems shall be in accordance with Section 507.4.2 through Section 507.4.2.3. Clearances from the duct or the
exhaust fan to the interior surface of enclosures of
combustible construction shall be in accordance with
Section 510.7.3 and clearances shall not be reduced.
303.10.1.2 Product Conveying Ducts. Reduced clearances to combustibles construction for product conveying ducts shall be in accordance with Section 506.10.3 through Section 506.11.6.3.
2025 CALIFORNIA MECHANICAL CODE 53
CMC § 303.10.1.3 High relevance — show source text
2025 CALIFORNIA MECHANICAL CODE 53
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303.10.1.3 Solid-Fuel-Burning Appliances. For solid-fuel-burning appliances, the clearance shall not be less than 12 inches (305 mm) to combustible walls and not less than 18 inches (457 mm) to combustible ceilings. The clearance, after reduction, shall be permitted to be less than 12 inches (305 mm) to combustible walls and less than 18 inches (457 mm) to combustible ceilings. Solid-fuel-burning appliances listed for lesser clearances shall be permitted to be installed in accordance with the manufacturer’s instructions and their listing. 303.11 Installation in Commercial Garages. Appliances installed in commercial garages shall be in accordance with Section 303.11.1 through Section 303.11.2. 303.11.1 Parking Structures. Appliances installed in enclosed, basement, and underground parking structures shall be installed in accordance with NFPA 88A. [NFPA 54:9.1.11.1] 303.11.2 Repair Garages. Appliances installed in repair garages shall be installed in accordance with NFPA 30A. [NFPA 54:9.1.11.2]
303.12 Installation in Aircraft Hangars. Heaters in aircraft hangars shall be installed in accordance with NFPA 409.
[NFPA 54:9.1.12]
304.0 Accessibility for Service. 304.1 General. All appliances shall be located with respect to building construction and other equipment so as to permit access for repair or replacement of the appliance. Clearance shall be maintained to permit removal of the appliance; cleaning of heating surfaces; the replacement of filters, blowers, motors, burners, controls, and vent connections; the lubrication of moving parts where necessary; the adjustment and cleaning of burners and pilots; and the proper functioning of explosion vents, if provided. For attic installation, the passageway and servicing area adjacent to the appliance shall be in accordance with Section 304.4. {NFPA 54:9.2.1}
Unless otherwise specified, clearances of not less than 30 inches (762 mm) in depth, width, and height of working space shall be maintained.
Exception: A platform shall not be required for unit heaters or room heaters.
304.2 Sloped Roof. Where equipment or appliances that require service are installed on a roof having a slope of 4 units vertical in 12 units horizontal (33 percent slope) or more, a level platform of not less than 30 inches by 30 inches (762 mm by 762 mm) shall be provided at the service side of the equipment or appliance. 304.3 Access to Appliances on Roofs. Appliances located on roofs or other elevated locations shall be accessible. [NFPA 54:9.4.3.1]
304.3.1 Access from the Inside. Buildings of more than 15 feet (4572 mm) in height shall have an inside means of access to the roof unless other means acceptable to the Authority Having Jurisdiction are used. [NFPA 54:9.4.3.2]
CMC § 508.2.1.1 High relevance — show source text
508.2.1.1 Guards and Rails. Guards or rails shall be required where the following exist:
(1) The clearance between the appliance and a roof edge or open end of an equipment platform is less than 6 feet (1829 mm).
(2) The open end of the equipment platform is located more than 30 inches (762 mm) above the roof, floor, or grade below.
Where guards or rails are installed, they shall be constructed so as to prevent the passage of a 21 inch (533 mm) diameter ball, resist the imposed loading conditions, and shall extend not less than 30 inches (762 mm) beyond each side of the equipment or appliance.
Exception: Guards shall not be required where a permanent fall arrest anchorage connector system in accordance with ASSP Z359.1 is installed.
508.2.2 Electrical Power. Appliances requiring an external source of electrical power shall be installed in accordance with NFPA 70. [NFPA 54:9.4.2.3]
508.2.3 Platform or Walkway. Where water stands on the roof at the appliance or in the passageways to the appliance, or where the roof is of a design having a water seal, a suitable platform, walkway, or both shall be provided above the water line. Such platform(s) or walkway(s) shall be located adjacent to the appliance and control panels so that the appliance can be safely serviced where water stands on the roof. [NFPA 54:9.4.2.4]
508.3 Appliances on Roofs. Appliances located on roofs or other elevated locations shall be accessible. [NFPA 54:9.4.3.1]
508.3.1 Access. Buildings of more than 15 feet (4572 mm) in height shall have an inside means of access to the roof, unless other means acceptable to the Authority Having Jurisdiction are used. [NFPA 54:9.4.3.2] 508.3.2 Access Type. The inside means of access shall be a permanent or foldaway inside stairway or ladder, terminating in an enclosure, scuttle, or trapdoor. Such scuttles or trapdoors shall be at least 22 inches by 24 inches (559 mm by 610 mm) in size, shall open easily and safely under all conditions, especially snow, and shall be constructed so as to permit access from the roof side unless deliberately locked on the inside.
At least 6 feet (1829 mm) of clearance shall be available between the access opening and the edge of the roof or similar hazard, or rigidly fixed rails or guards a minimum of 42 inches (1067 mm) in height shall be provided on the exposed side. Where parapets or other building structures
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bustion chamber. Bleed lines shall not terminate in positive-pressure-type combustion chambers. [NFPA 54:9.1.18]
507.22 Combination of Appliances and Equipment. Any combination of appliances, equipment, attachments, or devices used together in any manner shall comply with the standards that apply to the individual appliance and equipment. [NFPA 54:9.1.19]
507.23 Installation Instructions. The installer shall conform to the appliance and equipment manufacturers’ recommendations in completing an installation. The installer shall leave the manufacturers’ installation, operating, and maintenance instructions on the premises.
CMC § 304.4.3 High relevance — show source text
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GENERAL REGULATIONS
304.4.3 Work Platform. A level working platform not less than 30 inches by 30 inches (762 mm by 762 mm) shall be provided in front of the service side of the appliance. [NFPA 54:9.5.2]
Exception: A working platform need not be provided where the furnace is capable of being serviced from the required access opening. The furnace service side shall not exceed 12 inches (305 mm) from the access opening. 304.4.4 Lighting and Convenience Outlet. A permanent 120 V receptacle outlet and a luminaire shall be installed near the appliance. The switch controlling the luminaire shall be located at the entrance to the passageway. [NFPA 54:9.5.3]
305.0 Location.
305.1 Installation in Residential Garages. Appliances in residential garages and in adjacent spaces that open to the garage and are not part of the living space of a dwelling unit shall be installed so that all heating elements, switches, burners, and burner-ignition devices are located not less than 18 inches (457 mm) above the floor. Exception: Listed flammable vapor ignition resistant (FVIR) appliances. {NFPA 54:9.1.10.1} 305.1.1 Physical Damage. Appliances installed in garages, warehouses, or other areas subject to mechanical damage shall be guarded against such damage by being installed behind protective barriers or by being elevated or located out of the normal path of vehicles. 305.1.2 Access from the Outside. Where appliances are installed in a separate, enclosed space having access only from outside of the garage, such appliances shall be permitted to be installed at floor level, providing the required combustion air is taken from the exterior of the garage. [NFPA 54:9.1.10.3] 305.1.3 Cellulose Nitrate Plastic Storage. Heating equipment located in rooms where cellulose nitrate plastic is stored or processed shall be in accordance with the fire code.
305.2 Pit Location. Where excavation is necessary to install an appliance, the depth shall extend not less than 6 inches (152 mm) below and 12 inches (305 mm) on all sides of the appliance, except on the service side, which shall have 30 inches (762 mm). Where the depth of the excavation for either the appliance or passageway exceeds 12 inches (305 mm), walls shall be lined with concrete or masonry 4 inches (102 mm) above the adjoining ground level. Exception: [HCD 1 & HCD 2] Liquefied petroleum gas (LP-Gas) appliances as described in Section 303.7.1. 305.3 Flood Hazard Areas. For buildings located in flood hazard areas, heating, ventilating, air-conditioning, refrigeration, miscellaneous heat-producing, and energy-utilizing equipment and appliances shall be elevated at or above the elevation in accordance with the building code for utilities and attendant equipment or the elevation of the lowest floor, whichever is higher. Exception: Equipment and appliances shall be permitted to be located below the elevation in accordance with the build
CMC § 304.3.2 Medium relevance — show source text
304.3.2 Permanent Lighting. Permanent lighting shall be provided at the roof access. The switch for such lighting shall be located inside the building near the access means leading to the roof. [NFPA 54:9.4.3.4]
304.4 Appliances in Attics and Under-Floor Spaces. An attic or under-floor space in which an appliance is installed shall be accessible through an opening and passageway larger than the largest component of the appliance, and not less than 22 inches by 30 inches (559 mm by 762 mm). {NFPA 54:9.5.1}
304.4.1 Length of Passageway. Where the height of the passageway is less than 6 feet (1829 mm), the distance from the passageway access to the appliance shall not exceed 20 feet (6096 mm) measured along the centerline of the passageway. [NFPA 54:9.5.1.1] Where the height of the passageway is 6 feet (1829 mm) or more, the distance from the passageway access to the appliance shall not exceed 50 feet (15 240 mm) measured along the centerline of the passageway.
304.4.2 Width of Passageway. The passageway shall be unobstructed and shall have solid flooring not less than 24 inches (610 mm) wide from the entrance opening to the appliance. [NFPA 54:9.5.1.2]
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304.4.3 Work Platform. A level working platform not less than 30 inches by 30 inches (762 mm by 762 mm) shall be provided in front of the service side of the appliance. [NFPA 54:9.5.2]
Exception: A working platform need not be provided where the furnace is capable of being serviced from the required access opening. The furnace service side shall not exceed 12 inches (305 mm) from the access opening. 304.4.4 Lighting and Convenience Outlet. A permanent 120 V receptacle outlet and a luminaire shall be installed near the appliance. The switch controlling the luminaire shall be located at the entrance to the passageway. [NFPA 54:9.5.3]
305.0 Location.
305.1 Installation in Residential Garages. Appliances in residential garages and in adjacent spaces that open to the garage and are not part of the living space of a dwelling unit shall be installed so that all heating elements, switches, burners, and burner-ignition devices are located not less than 18 inches (457 mm) above the floor. Exception: Listed flammable vapor ignition resistant (FVIR) appliances. {NFPA 54:9.1.10.1} 305.1.1 Physical Damage. Appliances installed in garages, warehouses, or other areas subject to mechanical damage shall be guarded against such damage by being installed behind protective barriers or by being elevated or located out of the normal path of vehicles. **305.1.2 Access from the Outside.
CMC § 9.5.1 Medium relevance — show source text
** An attic or under-floor space in which an appliance is installed shall be accessible through an opening and passageway larger than the largest component of the appliance, and not less than 22 inches by 30 inches (559 mm by 762 mm). {NFPA 54:9.5.1} 508.4.1 Length of Passageway. Where the height of the passageway is less than 6 feet (1829 mm), the distance from the passageway access to the appliance shall not exceed 20 feet (6096 mm) measured along the centerline of the passageway. [NFPA 54:9.5.1.1] Where the height of the passageway is 6 feet (1829 mm) or more, the distance from the passageway access to the appliance shall not exceed 50 feet (15 240 mm) measured along the centerline of the passageway. 508.4.2 Width of Passageway. The passageway shall be unobstructed and shall have solid flooring not less than 24 inches (610 mm) wide from the entrance opening to the appliance. [NFPA 54:9.5.1.2] 508.4.3 Work Platform. A level working platform not less than 30 inches by 30 inches (762 mm by 762 mm) shall be provided in front of the service side of the appliance. [NFPA 54:9.5.2] 508.4.4 Lighting and Convenience Outlet. A permanent 120 V receptacle outlet and a luminaire shall be installed near the appliance. The switch controlling the luminaire shall be located at the entrance to the passageway. [NFPA 54:9.5.3]
509.0 Venting of Appliances. 509.1 Listing. Type B and Type B-W gas vents shall comply with UL 441, and Type L gas vents shall comply with UL 641. 509.1.1 Installation. Listed chimneys and vents shall be installed in accordance with Section 509.0 and the manufacturers’ installation instructions. [NFPA 54:12.2.1] 509.1.2 Prohibited Discharge. Appliance vents shall not discharge into a space enclosed by screens having openings less than [1] ⁄ 4 of an inch (6.4 mm) mesh. 509.2 Connection to Venting Systems. Except as permitted in Section 509.2.1 through Section 509.2.7, all appliances shall be connected to venting systems. [NFPA 54:12.3.1] 509.2.1 Appliances Not Required to be Vented. The following appliances shall not be required to be vented:
(1) A single listed booster-type (automatic instantaneous) water heater, when designed and used solely for the sanitizing rinse requirements of a dishwashing machine, provided that the appliance is installed with the draft hood in place and unaltered, if a draft hood is required, in a commercial kitchen having a mechanical exhaust system. [Where installed in this
manner, the draft hood outlet shall not be less than 36 inches (914 mm) vertically and 6 inches (152 mm) horizontally from any surface other than the appliance.] [NFPA 54:12.3.2(5)]
(2) Other appliances listed for unvented use and not provided with flue collars. [NFPA 54:12.3.2(10)] **509.2.2 Maximum Input Rating.
CMC § 1106.2.6. Medium relevance — show source text
(1) The space(s) containing the machinery is (are) separated from other occupancies by tight construction with tightfitting doors.
(2) Access is restricted to authorized personnel.
(3) Refrigerant detectors are installed with the sensing location and alarm level as required in refrigeration machinery rooms in accordance with Section 1106.2.6.
(4) Open flames and surfaces exceeding 800°F (427°C) shall not be permitted where a Group A2, B2, A3, or B3 refrigerant, is used.
(5) Electrical equipment that is in accordance with Class 1, Division 2, of NFPA 70 where the quantity of a Group A2, B2, A3, or B3 refrigerant in an independent circuit is capable of exceeding 25 percent of the lower flammability limit (LFL) upon release to the space based on the volume determined in accordance with Section 1104.2.1 through Section 1104.2.3.
(6) Refrigerant containing parts in systems exceeding 100 horsepower (74.6 kW) compressor drive power, except evaporators used for refrigeration or dehumidification, condensers used for heating, control and pressure-relief valves for either, low-probability pumps, and connecting piping, are located in a machinery room or outdoors.
[ASHRAE 15:7.2.2]
1104.5 Flammable Refrigerants. The total of Group A2, B2, A3, and B3 refrigerants, other than Group A2L and B2L refrigerants shall not exceed 1100 pounds (498.9 kg) without approval by the Authority Having Jurisdiction. Institutional Occupancies shall comply with Section 1104.3. Machinery rooms required in accordance with Section 1106.0 based on flammability shall be constructed and maintained in accordance with Section 1106.2.1 through Section 1106.2.6 and Section 1106.11 for Group A2L and B2L refrigerants. 1104.6 Group A2L Refrigerants for Human Comfort. High-probability systems using Group A2L refrigerants for human comfort applications shall comply with this section.
[ASHRAE 15:7.6]
1104.6.1 Refrigerant Concentration Limits. Occupied spaces shall comply with the releasable charge limitations of the equipment listing and ASHRAE 15. Unoccupied spaces with refrigerant containing equipment, not including continuous piping or tubing, shall comply with the releasable charge limitations of the equipment listing or Section 1104.6.4. {ASHRAE 15:7.6.1-7.6.1.2}
1104.6.2 Listing and Installation Requirements. Refrigeration systems shall be listed and shall be installed in accordance with listing, the manufacturer’s instructions, and any markings on the equipment restricting the installation. [ASHRAE 15:7.6.2]
1104.6.2.1 Nameplate. The nameplate required by Section 1115.5 shall include a symbol indicating that a flammable refrigerant is used, as specified by the product listing. [ASHRAE 15:7.6.2.1]
1104.6.2.2 Labeling. A label indicating a flammable refrigerant is used shall be placed adjacent to service ports and other locations where service involving components containing refrigerant is performed, as specified by the product listing.
CMC § 3.1 Medium relevance — show source text
K107.2 Rooftop platforms required. A rooftop platform shall be provided if the roof covering materials are:
1. Clay tile, concrete tile, slate shingles, wood shingles or wood shakes, and the roof slope is three units vertical in 12 units hori- zontal (25 percent slope) or greater.
2025 CALIFORNIA BUILDING CODE APPENDIX K-3
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX K—GROUP R-3 AND GROUP R-3.1 OCCUPANCIES PROTECTED BY THE FACILITIES OF THE CENTRAL VALLEY FLOOD PROTECTION PLAN
2. Metal roof panels or metal roof shingles, and the roof slope is one unit vertical in 12 units horizontal (8.33 percent slope) or greater.
K107.3 Roof live loads. Roof areas that are rooftop evacuation locations and roofs that support rooftop platforms that are evacuation locations shall be designed for the roof live load required for the occupancy as required in Table 1607.2.
K107.4 Evacuation routes to rooftop evacuation locations. Evacuation routes to rooftop evacuation locations shall be permitted to be provided by a stairway, ramp, alternating tread device, fixed ladder or other means approved by the building official.
Exception: In Group R-3.1 occupancies that are subject to the requirements of Chapter 11A or 11B, such requirements shall apply to the evacuation routes to rooftops.
K107.5 Perimeter protection. For Group R-3 and R-3.1 occupancies, the perimeter of rooftop evacuation locations shall be protected by:
1. Guards per Section 1013 if a rooftop platform is provided; or
2. A railing that is 12 inches (305 mm) in height if a sloped roof is provided.
K107.6 Utility/equipment buffer zone. A separation of 48 inches shall be provided between a rooftop evacuation location and any mechanical equipment, photovoltaic system, utility service drop or other utility line. Electrical service lines shall not pass over evacua- tion locations.
SECTION K108 — ATTICS THAT ARE EVACUATION LOCATIONS
K108.1 General. Attics that have finish floors no less than one (1) foot (0.30 meter) above the WSEL200 shall be permitted to be evacua- tion locations.
K108.2 Headroom. When an attic is used as an evacuation location, the minimum headroom of the required area shall be 30 inches (762 mm) with 50 percent of the required area having a headroom of 60 inches (1524 mm).
K108.3 Attic flooring. The required area of the evacuation location shall be solidly sheathed.
K108.4 Attic live loads. Attic areas that are used as evacuation locations shall be designed for the floor live load required for the occu- pancy as required in Table 1607.2.
K108.5 Evacuation routes to attic evacuation locations. Evacuation routes to attic evacuation locations shall be permitted to be provided by a stairway, ramp, alternating tread device, fixed ladder or other means approved by the building official.
CMC § 4.1.1 Medium relevance — show source text
R329.4.1.1 Roof load. Portions of roof structures not covered with photovoltaic panel systems shall be designed for dead loads and roof loads in accordance with Sections R301.4 and R301.6. Portions of roof structures covered with photovoltaic panel systems shall be designed for the following load cases:
- Dead load (including photovoltaic panel weight) plus snow load in accordance with Table R301.2.
- Dead load (excluding photovoltaic panel weight) plus roof live load or snow load, whichever is greater, in accordance with Section R301.6.
R329.4.1.2 Wind load. Rooftop-mounted photovoltaic panel or module systems and their supports shall be designed and installed to resist the component and cladding loads specified in Table R301.2.1(1), adjusted for height and exposure in accordance with Table R301.2.1(2).
R329.4.2 Fire classification. Rooftop-mounted photovoltaic panel systems shall have the same fire classification as the roof assembly required in Section R902.
R329.4.3 Roof penetrations. Roof penetrations shall be flashed and sealed in accordance with Chapter 9.
R329.5 Building-integrated photovoltaic systems. Building-integrated photovoltaic (BIPV) systems shall be designed and installed in accordance with Sections R329.5.1 through R329.5.2.
R329.5.1 BIPV roofing systems. BIPV roofing systems shall comply with Section R905.15. BIPV roof panels shall comply with Section R905.16.
R329.5.1.1 Fire classification. Building-integrated photovoltaic systems shall have a fire classification in accordance with Section R902.3.
R329.5.2 BIPV exterior wall coverings and fenestration. BIPV exterior wall coverings and fenestration shall comply with Section R705.
R329.6 Roof access and pathways. Roof access, pathways and setback requirements shall be provided in accordance with Sections R329.6.1 through R329.6.2.1. Access and minimum spacing shall be required to provide emergency access to the roof, to provide pathways to specific areas of the roof, provide for smoke ventilation opportunity areas, and to provide emergency egress from the roof.
Exceptions:
- Detached, nonhabitable structures, including but not limited to detached garages, parking shade structures, carports, solar trellises and similar structures, shall not be required to provide roof access.
- Roof access, pathways and setbacks need not be provided where the enforcing agency has determined that rooftop operations will not be employed.
- These requirements shall not apply to roofs with slopes of 2 units vertical in 12 units horizontal (17-percent slope) or less.
- BIPV systems listed in accordance with UL 3741, where the removal or cutting away of portions of the BIPV system during firefighting operations has been determined to not expose a firefighter to electrical shock hazards.
CMC § 90.1 Medium relevance — show source text
[ASHRAE 90.1:6.5.4.1]
2025 CALIFORNIA MECHANICAL CODE 439
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
APPENDIX E
TABLE E 503.5.7.2
PUMP FLOW CONTROL REQUIREMENTS
[ASHRAE 90.1: TABLE 6.5.4.2]
BOILER SYSTEM DESIGN INPUT, Btu/h MINIMUM TURNDOWN RATIO
≥1 000 000 and≤5 000 0003 to 1
>5 000 000 and≤10 000 0004 to 1
>10 000 0005 to 1 »
TABLE E 503.5.7
BOILER TURNDOWN
[ASHRAE 90.1: TABLE 6.5.4.1]
For SI units: 1000 British thermal units per hour = 0.293 kW
E 503.5.7.2 Hydronic Variable Flow Systems. Chilled- and hot-water distribution systems that include three or more control valves designed to modulate or step open and close as a function of load shall be designed for variable fluid flow and shall be capable of and configured to reduce pump flow rates to not more than the larger of 25 percent of the design flow rate or the minimum flow required by the heating/cooling equipment manufacturer for the proper operation of equipment. Individual or parallel pumps serving variable-flow heating-water or chilledwater systems, where the nameplate horsepower of the motor or combined parallel motors is not less than the power shown in Table E 503.5.7.2, shall have controls or devices that will result in pump motor demand of not more than 30 percent of design wattage at 50 percent of design water flow. The controls or devices shall be controlled as a function of desired flow or to
maintain a minimum required differential pressure. Differential pressure shall be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure. The differential pressure setpoint shall not exceed 110 percent of that required to achieve design flow through the heat exchanger. Where differential pressure control is used to comply with this section, and DDC systems are used, the setpoint shall be reset downward based on valve positions until one valve is nearly wide open.
Exceptions:
(1) Differential pressure set-point reset is not required where valve position is used to comply with Section E 503.5.7.4.
(2) Variable-pump flow control is not required on heating-water pumps where more than 50 percent of annual heat is generated by an electric boiler.
(3) Variable flow is not required for primary pumps in a primary/secondary system.
(4) Variable flow is not required for a coil pump provided for freeze protection.
(5) Variable flow is not required for heat recovery coil runaround loops. [ASHRAE 90.1:6.5.4.2]
Frequently asked questions
Do I always need a platform for every rooftop appliance?
Not always. Platforms are required where the roof ponds water or has a sealing surface (see § 303.8.6) or for equipment on slopes ≥ 4:12 (§ 304.2). Some small heaters (unit/room heaters) are excepted from platform requirements (§ 304.1).
What if my appliance is 5 feet from the roof edge?
Because 5 ft is less than the 6 ft clearance threshold, you must provide guards/rails per § 303.8.4.1 (42 in high, prevent passage of a 21-in ball, extend 30 in beyond the equipment). Alternatively, a compliant fall-arrest anchorage system may be accepted.
When does a building need inside access to the roof?
If the building is more than 15 feet in height, it must provide an inside means of access (permanent or foldaway stair/ladder to a scuttle/trapdoor), unless the AHJ approves another method. § 304.3.1.
What dimensions should a scuttle/trapdoor be?
Scuttles/trapdoors must be at least 22 in × 24 in and open easily and safely under all conditions. § 304.3.1.1.
Do ladder rungs need to support a specific load?
Yes — each ladder rung must be capable of supporting 300 pounds (136.1 kg) per § 304.3.1.2.
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