Do I Need a Permit to Replace a Furnace in California?

Furnace replacement permit requirements. Even same-model swaps need a mechanical permit. What inspectors check.

Yes — even a like-for-like furnace swap requires a mechanical permit.

In California

Furnace replacement is mechanical work under the California Mechanical Code, part of the same Title 24 package, so the combustion air, venting and clearance rules are statewide. California does not leave the code edition to the city. Health and Safety Code 17922 adopts Title 24 of the California Code of Regulations statewide, and requires that those standards 'impose substantially the same requirements as are contained in the most recent editions' of the named model codes, including 'The International Building Code of the International Code Council.' and 'The International Residential Code of the International Code Council.' A city or county may still vary it, but only on narrow grounds: under Health and Safety Code 17958.5 a local change must be 'reasonably necessary because of local climatic, geological, or topographical conditions', and under 17958.7 the governing body 'shall make an express finding' to that effect, file it with the California Building Standards Commission, and 'No modification or change shall become effective or operative for any purpose until the finding and the modification or change have been filed with the California Building Standards Commission.' AND THERE IS A LIVE FREEZE ON NEW RESIDENTIAL AMENDMENTS: 'Commencing October 1, 2025, to June 1, 2031, inclusive, a city or county shall not make a change or modification as described in subdivision (a) or (b), including to green building standards, that is applicable to residential units, unless one of the following conditions is met:' - broadly, that it is substantially equivalent to something already filed and in effect as of September 30, 2025, or the commission deems it necessary as an emergency standard. So for residential work today, expect the statewide code to govern and treat a NEW local residential amendment as the exception that has to justify itself.

Why Even a Swap Needs a Permit

Furnace replacements involve gas connections, venting, and combustion air — all safety-critical systems. Most jurisdictions require a mechanical permit to verify the new furnace is properly vented, has adequate combustion air, and the gas connections are leak-free. This is true even for exact same-model replacements.

High-Efficiency Conversions

Upgrading from a standard-efficiency (80%) to high-efficiency (90%+) furnace changes the venting requirements: standard units use metal B-vent, high-efficiency units use PVC/CPVC. The old metal vent chase may need to be sealed. A condensate drain line is also required for high-efficiency units.

What Inspectors Check

The final inspection covers: gas piping and drip leg, venting type and clearances, combustion air supply (especially in confined spaces), condensate drain (high-efficiency units), thermostat operation, and CO detector presence on every level.

Bundled with AC?

If you're replacing both the furnace and AC unit at the same time, one mechanical permit typically covers both. The inspector will check the AC refrigerant lines, electrical disconnect, and condenser pad in addition to the furnace items.

Yes, always. The permit is $40-$75 and your HVAC contractor handles it. One final inspection. Don't skip it — CO poisoning from bad venting is real.

Permit fees by city in California

Verified from each city’s published fee schedule. Where a city has no separate fee listed for this project, open the city page for the current requirements and amount.

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Permit fees by city in California
	Permit fee	Source
Fresno	Due at permit issuanceVerifiedvia Residential Building Permit	Residential Building Permit →
Long Beach	Per the City's published fee schedulesVerifiedvia Building Permit	Building Permit →
Oakland	NOT PUBLISHED on the pages readVerifiedvia Residential Building Combination Permit (RBC)	Residential Building Combination Permit (RBC) →
Sacramento	Published separately in the City's building fee pagesVerifiedvia Residential Building Permit	Residential Building Permit →
San Diego	$737.00Verifiedvia Residential Building Permit (Combination Building - Single Dwelling Units, ADUs and Duplexes)	Residential Building Permit (Combination Building - Single Dwelling Units, ADUs and Duplexes) →
San Jose	NOT PUBLISHED on the permit service pagesVerifiedvia Residential Building Permit (Standard Plan Review Service)	Residential Building Permit (Standard Plan Review Service) →

See the national overview for this permit →