CMC · California Mechanical Code
Where can I install fuel‑burning appliances (garages, attics, pits, roofs)?
If you’re installing a furnace, water heater or other fuel‑burning appliance in a garage, attic, pit or on a roof in California, the CMC requires that the appliance be serviceable and protected: in residential garages ignition components must be at least 18 inches above the floor (unless FVIR), attic/crawl installations need a minimum **22 × 30 in** opening, **24 in** wide solid passageway, and platform/lighting for service, and excavated pits require specific side and below clearances (6 in below, 12 in sides, 30 in service side) with wall lining when deeper than 12 in. See **§ 304.4**, **§ 305.1**, and **§ 305.2** for the controlling rules and follow appliance listings and AHJ guidance.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
In plain English: appliances must be located so they are serviceable, protected from damage, and meet minimum clearances and access requirements specific to the space where they are installed. Key CMC rules that control these locations are § 304.4, § 305.1, and § 305.2. For service access, working space, passageways and lighting see § 304.1 and § 304.4; for garage elevation/protection requirements see § 305.1; for appliance pits see § 305.2.
The single most important rule: place fuel‑burning appliances where they can be safely serviced and where ignition sources and hot components are protected from vehicle fumes, physical damage, and the people who occupy the space. See § 304.4, § 305.1, § 305.2.
Requirements in detail
Summary table — decision‑relevant dimensions & values
| Location / decision question | What the code requires (plain English) | Key dimensions / thresholds (bold) | Code Reference |
|---|---|---|---|
| Residential garage (appliance body and ignition parts) | Elevate ignition sources/heat-producing components above the garage floor so they are less likely to contact spilled vapors or vehicle fumes. | 18 inches above the floor (unless appliance is listed FVIR) | § 305.1 |
| Garage: protection from physical damage | Where subject to mechanical/vehicle damage, guard appliances (barriers, elevation, or locate out of vehicle path). | No numeric barrier spec in § 305.1 — must be guarded or elevated | § 305.1.1 |
| Garage: appliances in separate enclosed space with outside access | If the appliance room is only accessible from outside the garage, the appliance may be installed at floor level provided combustion air is drawn from exterior. | Floor level allowed only if exterior combustion air is provided | § 305.1.2 |
| Pit installations (excavated installation) | Excavation must provide minimum clearances around and below appliance; service side must be larger for service access. | 6 inches below appliance; 12 inches on all sides except service side = 30 inches; if excavation depth > 12 inches, line walls with concrete/masonry 4 inches above adjoining ground level | § 305.2 |
| Attic / under‑floor access opening | Opening & passageway must be larger than the largest appliance component and meet minimum opening size. | 22 in × 30 in minimum opening | § 304.4 |
| Passageway length (attic / crawl) | Limits on how far the appliance can be from the access depending on passageway height. | If passageway height < 6 ft: max 20 ft along centerline; if ≥ 6 ft: max 50 ft | § 304.4.1 |
| Passageway width & floor | Passageway must be unobstructed with solid flooring to the appliance. | 24 inches minimum solid flooring width from entrance to appliance | § 304.4.2 |
| Work platform at appliance service side | Platform required in front of service side for attic/under‑floor installed appliances. | 30 in × 30 in minimum platform; exception if furnace serviceable from access opening and service side ≤ 12 in from access | § 304.4.3 |
| Lighting & outlet for attic/under‑floor access | Provide permanent lighting and a receptacle near the appliance; switch at entrance. | 120 V luminaire and receptacle; switch at entrance | § 304.4.4 |
| General service clearances | Appliances must be located to permit repair/replacement and routine service. | Working space of 30 inches depth/width/height generally unless otherwise specified | § 304.1 |
Notes:
- Where code text grants an exception (for example, FVIR appliances in garages), that exception is explicit — consult the appliance listing/manufacturer and § 305.1.
- The CMC cross‑references NFPA and other standards for some specialized locations; follow those where the CMC invokes them.
Attics and under‑floor spaces (details)
- Access opening / passageway must be larger than the largest appliance component and at least 22 × 30 inches; the passageway must have solid flooring at least 24 inches wide to the appliance. § 304.4 and § 304.4.2 require these conditions.
- If the passage height is less than 6 feet, the appliance must be within 20 feet measured along the centerline of the passageway; if the passage height is 6 feet or more, the limit is 50 feet. § 304.4.1.
- Provide a 30 × 30 inch work platform at the service side per § 304.4.3 (unless the furnace can be serviced from the opening and its service side is ≤ 12 inches from the access).
- Provide permanent lighting and a 120 V outlet, with switch at the passage entrance per § 304.4.4.
Garages (residential) — elevation and protection
- Install so all heating elements, switches, burners and burner‑ignition devices are not less than 18 inches above the floor (unless the appliance is listed as FVIR). § 305.1.
- Where appliances are subject to mechanical/vehicle damage, guard them by barriers, elevating them, or locating them out of vehicle paths (§ 305.1.1).
- If the appliance is inside a separate enclosed space that is accessible only from outside the garage, floor‑level installation is permitted provided combustion air is taken from the exterior (§ 305.1.2).
Pits (excavation) — minimum clearances & lining
- Excavation must extend not less than 6 inches below the appliance and 12 inches on all sides except the service side, which must have 30 inches clearance. If the excavation depth for the appliance or passageway exceeds 12 inches, lining the pit walls with concrete or masonry is required, extending 4 inches above the adjoining ground level (§ 305.2).
- The code provides an exception for some LP‑Gas appliances referencing HCD requirements and § 303.7.1; the details of that exception (HCD 1 & HCD 2 application) are addressed in § 305.2 and the LP‑gas section § 303.7.1. The full LP‑Gas exception text is not reproduced here; consult § 303.7.1 and the referenced HCD rules for the complete allowance.
Exceptions & special cases
- FVIR appliances: the 18‑inch elevation requirement in garages does not apply to appliances listed as flammable vapor ignition resistant (FVIR) — see § 305.1. Always confirm the appliance listing and manufacturer instructions.
- Separate, outside‑access appliance rooms in garages: allowed at floor level only if combustion air is taken from exterior — § 305.1.2.
- Pit exceptions for certain LP‑Gas appliances are noted in § 305.2 and reference HCD/§ 303.7.1; details for those special allowances must be checked in the LP‑Gas section and HCD guidance (text not fully reproduced here).
- Manufacturer’s listing or installation instructions may provide reduced clearances or alternate allowances; where the CMC defers to listings/instructions, follow the listed appliance instructions and document them for the AHJ. See general cross‑references in Chapter 3 (installation and clearances) and § 304.1.
Common mistakes
- Placing a water heater or furnace in a garage at floor level without providing exterior combustion air when the appliance room is not exclusively outside‑accessible (violates § 305.1.2 unless criteria met).
- Forgetting to elevate burners/ignition components 18 inches in a residential garage (unless FVIR) — watch for hidden ignition sources such as ignitor modules and switches (§ 305.1).
- Installing an attic furnace but providing an access opening smaller than 22 × 30 inches, or leaving the passageway < 24 inches wide or too long for the passage height (violates § 304.4, § 304.4.1–4.2).
- Omitting the 30 × 30 inch service platform or failing to provide the required luminaire and 120 V receptacle at attic/crawl installations (see § 304.4.3–4.4).
- Assuming Building Code garage appliance elevation rules are identical to CMC — always check the CMC appliance sections and the Building Code cross‑references where applicable (e.g., vehicle clearance heights).
Worked example — attic furnace installation (concrete numbers)
Situation: You need to install a gas furnace in an attic. The furnace largest component (cabinet) is 20 in wide × 28 in long; the attic access is a scuttle and the passageway is 5 ft high.
Apply the rules:
- Access opening: must be larger than the largest component and at least 22 × 30 inches. Your component is 20 × 28 in, so the 22 × 30 in minimum opening is satisfied — § 304.4.
- Passageway height is 5 ft (< 6 ft), so appliance must be within 20 feet measured along the centerline of the passageway from the access opening — § 304.4.1. If the furnace sits 18 feet down the passage, that is acceptable; if it is 25 feet, it is not.
- Passageway flooring: provide unobstructed solid flooring at least 24 inches wide from the entrance to the appliance — § 304.4.2.
- Service platform: provide a 30 × 30 inch platform at the service side of the furnace unless the furnace can be serviced from the access opening and the service side is ≤ 12 inches from that opening — § 304.4.3. If the furnace service side is 14 inches from the opening, you must provide the platform.
- Lighting & outlet: install a permanent luminaire and a 120 V receptacle near the furnace with the luminaire switch at the entrance — § 304.4.4.
If any of these items cannot be met, you must revise the installation location or provide acceptable alternative means approved by the AHJ.
Related provisions (CMC)
- § 304.1 — General servicing clearances and required working space.
- § 303.7 / § 303.7.1 — Liquefied petroleum gas (LP‑Gas) appliance requirements and related exceptions referenced by § 305.2 (pit exception). (See LP‑Gas section for details.)
- § 303.8 — Appliances on roofs (access and mounting considerations).
- § 303.10.1 — Clearance to combustible construction (where appliance listings/clearances are given).
If you need a specific manufacturer’s listing or an AHJ interpretation (for example, for a custom pit arrangement or a non‑standard attic configuration), check the appliance listing and coordinate with the local building official.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
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 § 9.2.2 High relevance — show source text
** 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.
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GENERAL REGULATIONS
»
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]
CMC § 303.7 High relevance — show source text
303.7 Liquefied Petroleum Gas (LP-Gas) Facilities . . . . . . . . . . . . . . 53
303.8 Appliances on Roofs. . . . . . . . . . . . 53
303.9 Avoiding Strain on Gas Piping . . . . 53
303.10 Clearance to Combustible
Materials . . . . . . . . . . . . . . . . . . . . . 53
303.11 Installation in Commercial
Garages . . . . . . . . . . . . . . . . . . . . . 54
303.12 Installation in Aircraft Hangars . . . . 54
304.0 Accessibility for Service . . . . . . . . . 54
304.1 General. . . . . . . . . . . . . . . . . . . . . . 54
304.2 Sloped Roof . . . . . . . . . . . . . . . . . . 54
304.3 Access to Appliances on Roofs . . . 54
304.4 Appliances in Attics and Under-Floor Spaces . . . . . . . . . . . . 54
305.0 Location . . . . . . . . . . . . . . . . . . . . . 55
305.1 Installation in Residential Garages . . 55
305.2 Pit Location. . . . . . . . . . . . . . . . . . . 55
305.3 Flood Hazard Areas . . . . . . . . . . . . 55
305.4 Elevator Shaft . . . . . . . . . . . . . . . . . 55
305.5 Drainage Pan . . . . . . . . . . . . . . . . . 55
305.6 Outdoor Locations . . . . . . . . . . . . . 55
306.0 Automatic Control Devices . . . . . . . 55
306.1 General. . . . . . . . . . . . . . . . . . . . . . 55
306.2 Building Automation Systems . . . . 56
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TABLE OF CONTENTS
307.0 Labeling . . . . . . . . . . . . . . . . . . . . . 56
307.1 Fuel-Burning Appliances . . . . . . . . 56
307.2 Electric Heating Appliances . . . . . . 56
307.3 Heat Pump and Electric Cooling Appliances . . . . . . . . . . . . . . . . . . . 56
307.4 Absorption Units . . . . . . . . . . . . . . . 56
308.0 Improper Location. . . . . . . . . . . . . . 57
308.1 General. . . . . . . . . . . . . . . . . . . . . . 57
309.0 Workmanship . . . . . . . . . . . . . . . . . 57
309.1 Engineering Practices. . . . . . . . . . . 57
309.2 Concealing Imperfections . . . . . . . . 57
309.3 Installation Practices. . . . . . . . . . . . 57
CMC § 406.2.9.1.1 High relevance — show source text
Exception: Elevation of the ignition source is not required for appliances that are listed as flammable vapor ignition resistant.
406.2.9.1.1 Parking garages. Connection of a parking garage with any room in which there is a fuel-fired appliance shall be by means of a vestibule providing a two-doorway separation, except that a single door is permitted where the sources of ignition in the appliance are elevated in accordance with Section 406.2.9.
Exception: This section shall not apply to appliance installations complying with Section 406.2.9.2 or 406.2.9.3.
406.2.9.2 Public garages. Appliances located in public garages, motor fuel-dispensing facilities, repair garages or other areas frequented by motor vehicles shall be installed not less than 8 feet (2438 mm) above the floor. Where motor vehicles are capa
2025 CALIFORNIA BUILDING CODE 4-15
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE
ble of passing under an appliance, the appliance shall be installed at the clearances required by the appliance manufacturer and not less than 1 foot (305 mm) higher than the tallest vehicle garage door opening.
Exception: The requirements of this section shall not apply where the appliances are protected from motor vehicle impact and installed in accordance with Section 406.2.9.1 and NFPA 30A.
406.2.9.3 Private garages. Appliances located in private garages and carports shall be installed with a minimum clearance of 6 feet (1829 mm) above the floor.
Exception: The requirements of this section shall not apply where the appliances are protected from motor vehicle impact and are installed in accordance with Section 406.2.9.1.
406.3 Private garages and carports. Private garages and carports shall comply with Sections 406.2 and 406.3, or they shall comply with Sections 406.2 and 406.4.
406.3.1 Classification. Private garages and carports shall be classified as Group U occupancies. Each private garage shall be not greater than 1,000 square feet (93 m [2] ) in area. Multiple private garages are permitted in a building where each private garage is separated from the other private garages by 1-hour fire barriers in accordance with Section 707, or 1-hour horizontal assemblies in accordance with Section 711, or both.
Exception: The area of a private garage accessory to Group R-3 one- or two-family dwellings shall not be greater than 3,000 square feet in area.
406.3.2 Separation. For other than private garages adjacent to dwelling units, the separation of private garages from other occupancies shall comply with Section 508. Separation of private garages from dwelling units shall comply with Sections 406.3.2.1 and 406.3.2.2.
406.3.2.1 Dwelling unit separation. The private garage shall be separated from the dwelling unit and its attic area by means of gypsum board, not less than [1] / 2 inch (12.7 mm) in thickness, applied to the garage side.
CMC § 25.4 High relevance — show source text
joist or
roof truss to
top track of
bearing wallb|24|40|6|6|8|10|10| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 mil = 0.0254 mm.
a. Screws are a minimum No. 10 unless noted otherwise.
b. Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle. See Section R804.3.8 for additional
requirements to resist uplift forces.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 mil = 0.0254 mm.
a. Screws are a minimum No. 10 unless noted otherwise.
b. Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle. See Section R804.3.8 for additional
requirements to resist uplift forces.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 mil = 0.0254 mm.
a. Screws are a minimum No. 10 unless noted otherwise.
b. Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle. See Section R804.3.8 for additional
requirements to resist uplift forces.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 mil = 0.0254 mm.
a. Screws are a minimum No. 10 unless noted otherwise.
b. Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle. See Section R804.3.8 for additional
requirements to resist uplift forces.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 mil = 0.0254 mm.
a. Screws are a minimum No. 10 unless noted otherwise.
b. Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle. See Section R804.3.8 for additional
requirements to resist uplift forces.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 mil = 0.0254 mm.
a. Screws are a minimum No. 10 unless noted otherwise.
b. Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle.CMC § 406.2.5 High relevance — show source text
406.2.5 Sleeping rooms. Openings between a motor vehicle-related occupancy and a room used for sleeping purposes shall not be permitted.
406.2.6 Fuel dispensing. The dispensing of fuel shall only be permitted in motor fuel-dispensing facilities in accordance with Section 406.7.
406.2.7 Electric vehicle charging stations and systems. Where provided, electric vehicle charging systems shall be installed in accordance with the California Electrical Code and the California Green Building Standards Code . Electric vehicle charging system equipment shall be listed and labeled in accordance with UL 2202. Electric vehicle supply equipment shall be listed and labeled in accordance with UL 2594. Accessibility to electric vehicle charging stations shall be provided in accordance with Chapters 11A and/or 11B.
406.2.8 Mixed occupancies and uses. Mixed uses shall be allowed in the same building as public parking garages and repair garages in accordance with Section 508.1. Mixed uses in the same building as an open parking garage are subject to Sections 402.4.2.3, 406.5.11, 508.1, 510.3, 510.4 and 510.7.
406.2.9 Equipment and appliances. Equipment and appliances shall be installed in accordance with Sections 406.2.9.1 through 406.2.9.3 and the California Mechanical Code, California Plumbing Code and California Electrical Code.
406.2.9.1 Elevation of ignition sources. Equipment and appliances having an ignition source and located in hazardous locations and public garages, private garages, repair garages, automotive motor fuel-dispensing facilities and parking garages shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor surface on which the equipment or appliance rests. For the purpose of this section, rooms or spaces that are not part of the living space of a dwelling unit and that communicate directly with a private garage through openings shall be considered to be part of the private garage.
Exception: Elevation of the ignition source is not required for appliances that are listed as flammable vapor ignition resistant.
406.2.9.1.1 Parking garages. Connection of a parking garage with any room in which there is a fuel-fired appliance shall be by means of a vestibule providing a two-doorway separation, except that a single door is permitted where the sources of ignition in the appliance are elevated in accordance with Section 406.2.9.
Exception: This section shall not apply to appliance installations complying with Section 406.2.9.2 or 406.2.9.3.
406.2.9.2 Public garages. Appliances located in public garages, motor fuel-dispensing facilities, repair garages or other areas frequented by motor vehicles shall be installed not less than 8 feet (2438 mm) above the floor. Where motor vehicles are capa
2025 CALIFORNIA BUILDING CODE 4-15
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE
ble of passing under an appliance, the appliance shall be installed at the clearances required by the appliance manufacturer and not less than 1 foot (305 mm) higher than the tallest vehicle garage door opening.
CMC § 304.8 High relevance — show source text
700
17 000|41 100
39 200
37 500
36 000
34 700| |800
850
900
950
1000|250
242
235
228
222|523
506
490
476
463|985
953
924
897
873|2020
1960
1900
1840
1790|3030
2930
2840
2760
2680|5830
5640
5470
5310
5170|9300
9000
8720
8470
8240|16 400
15 900
15 400
15 000
14 600|33 500
32 400
31 500
30 500
29 700| |1100
1200
1300
1400
1500|210
201
192
185
178|440
420
402
386
372|829
791
757
727
701|1700
1620
1550
1490
1440|2550
2430
2330
2240
2160|4910
4680
4490
4310
4150|7830
7470
7150
6870
6620|13 800
13 200
12 600
12 100
11 700|28 200
26 900
25 800
24 800
23 900| |1600
1700
1800
1900
2000|172
166
161
157
152|359
348
337
327
318|677
655
635
617
600|1390
1340
1300
1270
1230|2080
2010
1950
1900
1840|4010
3880
3760
3650
3550|6390
6180
6000
5820
5660|11 300
10 900
10 600
10 300
10 000|23 000
22 300
21 600
21 000
20 400|For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 pound-force per square inch = 6.8947 kPa
- Table entries are rounded to 3 significant digits.
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FUEL GAS PIPING
CMC § 406.2.2 High relevance — show source text
406.2.2 Clear height. The clear height of each floor level in vehicle and pedestrian traffic areas shall be not less than 7 feet (2134 mm). Canopies under which fuels are dispensed shall have a clear height in accordance with Section 406.7.2. [DSA-AC, HCD 1-AC] The clear height of vehicle and pedestrian areas required to be accessible shall comply with Chapter 11A or 11B, as applicable.
Exception: A lower clear height is permitted for a parking tier in mechanical-access open parking garages where approved by the building official.
[BE] 406.2.3 Accessible parking spaces. Where parking is provided, accessible parking spaces, access aisles and vehicular routes serving accessible parking shall be provided in accordance with Chapter 11A or Chapter 11B, as applicable.
406.2.4 Floor surfaces. Floor surfaces shall be of concrete or similar approved noncombustible and nonabsorbent materials. The area of floor used for the parking of automobiles or other vehicles shall be sloped to facilitate the movement of liquids to a drain or toward the main vehicle entry doorway. The surface of vehicle fueling pads in motor fuel-dispensing facilities shall be in accordance with Section 406.7.1.
Exceptions:
- Asphalt parking surfaces shall be permitted at ground level for public parking garages and private carports.
- Slip-resistant, nonabsorbent, interior floor finishes having a critical radiant flux not more than 0.45 W/cm [2], as determined by ASTM E648 or NFPA 253, shall be permitted in repair garages.
406.2.5 Sleeping rooms. Openings between a motor vehicle-related occupancy and a room used for sleeping purposes shall not be permitted.
406.2.6 Fuel dispensing. The dispensing of fuel shall only be permitted in motor fuel-dispensing facilities in accordance with Section 406.7.
406.2.7 Electric vehicle charging stations and systems. Where provided, electric vehicle charging systems shall be installed in accordance with the California Electrical Code and the California Green Building Standards Code . Electric vehicle charging system equipment shall be listed and labeled in accordance with UL 2202. Electric vehicle supply equipment shall be listed and labeled in accordance with UL 2594. Accessibility to electric vehicle charging stations shall be provided in accordance with Chapters 11A and/or 11B.
406.2.8 Mixed occupancies and uses. Mixed uses shall be allowed in the same building as public parking garages and repair garages in accordance with Section 508.1. Mixed uses in the same building as an open parking garage are subject to Sections 402.4.2.3, 406.5.11, 508.1, 510.3, 510.4 and 510.7.
406.2.9 Equipment and appliances. Equipment and appliances shall be installed in accordance with Sections 406.2.9.1 through 406.2.9.3 and the California Mechanical Code, California Plumbing Code and California Electrical Code.
CMC § 304.3.2 High 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]
54 2025 CALIFORNIA MECHANICAL CODE
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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.
CMC § 2113.11 High relevance — show source text
2113.11 Flue lining (material). Masonry chimneys shall be lined. The lining material shall be appropriate for the type of appliance connected, according to the terms of the appliance listing and the manufacturer’s instructions.
2113.11.1 Residential-type appliances (general). Flue lining systems shall comply with one of the following:
- Clay flue lining complying with the requirements of ASTM C315.
- Listed chimney lining systems complying with UL 1777.
- Factory-built chimneys or chimney units listed for installation within masonry chimneys.
- Other approved materials that will resist corrosion, erosion, softening or cracking from flue gases and condensate at temperatures up to 1,800°F (982°C).
2113.11.1.1 Flue linings for specific appliances. Flue linings other than those covered in Section 2113.11.1 intended for use with specific appliances shall comply with Sections 2113.11.1.2 through 2113.11.1.4, 2113.11.2 and 2113.11.3.
2113.11.1.2 Gas appliances. Flue lining systems for gas appliances shall be in accordance with the California Mechanical Code .
2113.11.1.3 Pellet fuel-burning appliances. Flue lining and vent systems for use in masonry chimneys with pellet fuel-burning appliances shall be limited to flue lining systems complying with Section 2113.11.1 and pellet vents listed for installation within masonry chimneys (see Section 2113.11.1.5 for marking).
2113.11.1.4 Oil-fired appliances approved for use with L-vent. Flue lining and vent systems for use in masonry chimneys with oil-fired appliances approved for use with Type L vent shall be limited to flue lining systems complying with Section 2113.11.1 and listed chimney liners complying with UL 641 (see Section 2113.11.1.5 for marking).
2113.11.1.5 Notice of usage. When a flue is relined with a material not complying with Section 2113.11.1, the chimney shall be plainly and permanently identified by a label attached to a wall, ceiling or other conspicuous location adjacent to where the connector enters the chimney. The label shall include the following message or equivalent language: “This chimney is for use only with (type or category of appliance) that burns (type of fuel). Do not connect other types of appliances.”
2113.11.2 Concrete and masonry chimneys for medium-heat appliances. Concrete and masonry chimneys for medium-heat appliances shall comply with Sections 2113.11.2.1 through 2113.11.2.5.
2113.11.2.1 Construction. Chimneys for medium-heat appliances shall be constructed of solid masonry units or of concrete with walls not less than 8 inches (203 mm) thick, or with stone masonry not less than 12 inches (305 mm) thick.
CMC § 303.10.1.3 High relevance — show source text
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GENERAL REGULATIONS
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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 § 304.8 High relevance — show source text
r>| |125
|87
|173
|313
|542
|819
|1470
|4070
|7900
| |150
|78
|157
|284
|491
|742
|1330
|3690
|7130
| |175
|72
|145
|261
|452
|683
|1230
|3390
|6560
| |200
|67
|135
|243
|420
|635
|1140
|3160
|6100
| |250
|60
|119
|215
|373
|563
|1010
|2800
|5410
| |300
|54
|108
|195
|338
|510
|916
|2530
|4900
| |350
|50
|99
|179
|311
|469
|843
|2330
|4510
| |400
|46
|92
|167
|289
|436
|784
|2170
|4190
| |450
|43
|87
|157
|271
|409
|736
|2040
|3930
| |500|41|82|148|256|387|695|1920|3720|For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 inch water column = 0.249 kPa
- Table entries are rounded to 3 significant digits.
Frequently asked questions
Can I install a gas water heater on the garage floor?
Only if the heater is in a separate enclosed space with access only from outside the garage and the required combustion air is taken from the exterior (see § 305.1.2). Otherwise heating elements and ignition devices in residential garages must be installed so they are not less than 18 inches above the floor unless the appliance is listed FVIR (§ 305.1).
Is a 20 × 24 inch attic access opening acceptable for appliance installation?
No. The code requires the opening and passageway be larger than the largest appliance component and not less than 22 × 30 inches for appliances installed in attics or under‑floor spaces (§ 304.4).
Do I always need a 30 × 30 inch platform in an attic?
A 30 × 30 inch platform is required at the service side of the appliance per § 304.4.3, except where the furnace is capable of being serviced from the required access opening and the furnace service side is within 12 inches of that opening.
What if my pit depth is 14 inches — do I need lining?
Yes. If the depth of the excavation for the appliance or passageway exceeds 12 inches, the walls must be lined with concrete or masonry and extend 4 inches above the adjoining ground per § 305.2.
Does appliance listing override these location rules?
Where the CMC defers to a listed appliance (e.g., reduced combustible clearances or FVIR listings), follow the appliance listing and manufacturer instructions — but you still must meet access, platform, and other location requirements found in § 304.1 and § 304.4 unless the code or AHJ grants an exception.
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