The furnace dies in January. The first company to answer the phone can be there tomorrow and quotes a number. The second one is three days out, quotes more, and mentions a permit and an inspection. It is tempting to read that as padding. It is closer to the opposite — a signal that the second company expects the work to be looked at.
California's heating, cooling and ventilation rules live in the California Mechanical Code, one part of the state's building standards. It does not decide your city's permit thresholds — but it does publish a permit fee schedule naming each kind of mechanical job a jurisdiction bills for, from a furnace over or under 100,000 British thermal units per hour to a single ventilation fan on one duct (Chapter 1). That list is the closest thing to a statewide map of what counts as permit work.
Key numbers
| Equipment | Where the code draws its line | Where it says so |
|---|---|---|
| Forced-air or gravity furnace | Separate fee lines at 100,000 Btu/h and above | Chapter 1 fee schedule |
| Boilers and compressors | Brackets at 3, 15, 30 and 50 horsepower | Chapter 1 fee schedule |
| Air handling units | Split at 10,000 cubic feet per minute | Chapter 1 fee schedule |
| Gas piping | Priced per system of one to five outlets, then per outlet | Chapter 1 fee schedule |
| After-hours inspection | Hourly, 2-hour minimum | Chapter 1 fee schedule |
| Extra plan review after revisions | Hourly, half-hour minimum | Chapter 1 fee schedule |
What's on the list
Read the schedule as an inventory of work the state expects to be inspected somewhere in California:
- Furnaces — installing or relocating a forced-air or gravity furnace or burner, including attached ducts and vents, with a separate line above 100,000 Btu/h; floor furnaces including their vent; suspended heaters, recessed wall heaters and floor-mounted unit heaters
- Appliance vents installed or replaced on their own, outside an appliance permit
- Repairs and additions to a heating appliance, refrigeration unit, cooling unit, absorption unit, or a heating, cooling, absorption or evaporative cooling system — explicitly including the controls
- Boilers and compressors, bracketed by horsepower, and absorption systems bracketed by Btu/h
- Air handlers at or above 10,000 cubic feet per minute, and evaporative coolers other than the portable type
- Ventilation and exhaust — each fan on a single duct, each ventilation system not covered by an existing heating or air-conditioning permit, and each hood served by mechanical exhaust, with its ducts
- Fuel gas piping, priced by outlet count, and process piping for hazardous and nonhazardous systems
- A catch-all line for any appliance regulated by the code that fits no other category
Two details in that list are worth pausing on. The controls clause means a "simple" thermostat-and-zoning upgrade can land in permit territory. And the phrase other than portable type is why a window or roll-around cooler is treated differently from an installed one — the code's interest starts when equipment becomes part of the building.
The prices are not the state's business
The most revealing thing in the schedule is what is missing. Every dollar figure is blank, with a single footnote:
"Jurisdiction will indicate their fees here." — Chapter 1 fee schedule
That is the division of labour in California building regulation in one line. The state standardises what gets regulated; your city or county decides what it costs, when a permit is required for small work, and how inspections are scheduled. Two houses on either side of a city limit can face the same technical rules and completely different counter experiences.
It also explains the fees that surprise people at the end of a job. Inspections outside normal business hours are billed by the hour with a two-hour minimum. Reinspections — the second visit after a correction — are their own line. So is additional plan review when drawings change after review has started, hourly with a half-hour minimum. None of these are penalties. They are the schedule doing exactly what it says.
Two rules that catch remodels
Changing what a space is used for restarts the analysis. Mechanical systems in a building undergoing a change in use or occupancy must comply with the requirements that apply to the new use, not the one they were installed under (§ 102.6). Converting a garage or an outbuilding into conditioned living space is the common case.
And an appeal is not an exemption. If you disagree with how an inspector applied a provision, there is a board of appeals — but the code states plainly that it "shall have no authority relative to interpretation of the administrative provisions of this code," nor may it waive the code's requirements (§ 107.2). The plumbing code carries that limitation in identical words (§ 107.2), which tells you it is a deliberate, shared rule about how these codes are administered rather than a quirk of one book. Appeals resolve genuine disputes about application. The flexibility for unusual designs lives elsewhere, in approvals of alternate materials and methods.
What this doesn't answer
The fee schedule tells you what jurisdictions charge for; it does not tell you what your jurisdiction requires. Small-work exemptions, like-for-like replacement policies and contractor-versus-homeowner rules are all local, and they differ. Before scheduling equipment work, ask the building department two questions: does this need a permit, and does it need an inspection before the wall closes. Plain-English guides to the rest of California's code parts are on our building codes hub.
Sources
- 2025 California Mechanical Code, Chapter 1 — permit fee schedule and inspection fees
- 2025 California Mechanical Code § 102.6 — changes in building occupancy
- 2025 California Mechanical Code § 107.2 — limitations of the appeals board
- 2025 California Plumbing Code § 107.2 — the identical appeals limitation
