Research by DoINeedAPermit Research Team · Updated May 2026
The Short Answer
Most HVAC work in Lomita requires a permit from the City of Lomita Building Department. Replacements, new installations, and modifications to ductwork or refrigerant lines all need sign-off. Owner-builders can pull permits themselves, but the work must still pass inspection.
Lomita's building department treats HVAC systems as mechanical systems under Title 24 and the California Mechanical Code, meaning virtually all work beyond simple filter changes requires a permit. What sets Lomita apart from neighboring unincorporated areas is that the city has adopted the 2022 California Building Code with local amendments — you can't just assume 'it's California, so it's the same everywhere.' Lomita sits in both coastal (3B-3C climate zone) and foothill (5B-6B) areas, which affects equipment sizing requirements and ductwork insulation standards; the code requires different R-values depending on whether your HVAC serves a coastal or mountain zone, and Lomita's plan reviewers will catch mismatches. The city allows owner-builders to pull mechanical permits under California Business & Professions Code § 7044, but electrical work (thermostat wiring, disconnect switches) still requires a licensed electrician — that's a common sticking point homeowners miss. Plan review typically takes 5-10 business days for standard replacements, though complex ductwork redesigns may trigger a full mechanical engineer review (adding 2-3 weeks). Permit fees run roughly $200–$600 depending on system cost and scope, calculated as a percentage of the estimated work value.

What happens if you skip the permit (and you needed one)

Lomita HVAC permits — the key details

Lomita has adopted the 2022 California Building Code with Title 24 Part 6 energy standards baked in. The California Mechanical Code (Chapter 15 of the CBC) governs all HVAC permits in the city. What triggers a permit in Lomita: any new system installation, any replacement of an existing system (even like-for-like), any modification to ductwork or refrigerant piping, any change to equipment capacity or location, and any thermostat upgrades that involve new wiring or disconnect switches. The city's definition of 'replacement' is broad — swapping out a furnace or air conditioner requires a full permit and inspection, even if you're putting in identical equipment in the same location. This is stricter than some unincorporated county areas that allow 'same-capacity replacement' without permits. Lomita's building department will ask for the equipment model number, tonnage/BTU, efficiency rating, and proposed location during permit intake. If your replacement system is a higher capacity than the original, the city will require a load calculation (ACCA Manual J or equivalent) to verify your ducts and electrical supply can handle it. If it's lower capacity, you may still need to show that existing ductwork remains adequate.

The electrical component is where many owner-builders get tripped up. California Business & Professions Code § 7044 allows owner-builders to pull and perform their own mechanical work, but Section 7047 carves out electrical work — any wiring, thermostat controls, disconnect switches, or power connections must be done by a licensed electrician with a C-10 (Electrical) license. Lomita's building department will not sign off on a mechanical permit if the electrical rough-in hasn't been inspected by a licensed electrician. This means if you're replacing a furnace, you can do the physical swap yourself (as an owner-builder), but a C-10 must handle the thermostat wiring, the 240-volt disconnect switch installation, and the breaker connection. Many homeowners hire a licensed HVAC contractor specifically to avoid this split-trade problem, since HVAC contractors are licensed as both mechanical and electrical specialists in California. If you do want to pull the permit yourself, budget $800–$1,500 for the electrician's portion of the job (thermostat wiring, disconnect switch, breaker) on top of whatever you're paying for labor or equipment.

Lomita's permit fee structure is based on the estimated cost of the work, not just the equipment price. For a typical furnace or air conditioner replacement (equipment + labor), the city calculates fees at roughly 1.5-2% of the total estimated project cost. A $5,000 furnace replacement (equipment + labor) would generate a permit fee of $75–$100. A $12,000 air conditioning system with ductwork modifications might be $180–$240 in permit fees. The city also charges for inspections — typically one rough-in inspection (ductwork/piping before final connections) and one final inspection (system operational, controls verified). There's no extra fee per inspection; it's bundled into the permit cost. Plan review takes 5-10 business days for standard replacements; if the city asks for revisions (e.g., 'ductwork in attic needs R-8 insulation per Title 24'), resubmission and re-review add another 3-5 days. If your project involves ductwork in a conditioned space (like a basement or interior wall), Lomita may require an energy audit or HVAC contractor pre-sign-off before permit issuance, adding another week.

Lomita's location spanning coastal and mountain climate zones creates a unique compliance wrinkle. Title 24 Part 6 specifies different insulation requirements for HVAC ducts depending on zone: coastal properties (3B-3C) require minimum R-6 duct insulation, while foothill properties (5B-6B) require R-8 in some cases. Lomita's building department applies these rules by property address — if your home is in the coastal zone (most of Lomita proper), R-6 suffices; if it's in the foothills, the city will ask for R-8 wrap or equivalent. This also affects thermostat setpoints and controls: Title 24 requires 'demand responsive controls' (automatic setback overnight or when unoccupied) for new systems, and Lomita inspectors will check that your new thermostat has this capability. Many older homes still have manual thermostats without setback — replacing just the furnace/AC won't trigger a full thermostat upgrade requirement, but adding new ductwork or doing a full system rebuild (furnace + coil + ducts) may require a programmable or smart thermostat with remote setback. Budget $150–$400 for a Title 24-compliant smart thermostat if you're doing a full system.

The practical path forward: contact Lomita's building department (City of Lomita Building Department, typically accessible through city hall) with your equipment specs and a rough scope (replacement vs. new installation, ductwork changes yes/no, location). They'll tell you whether a permit is needed and what documents to submit — usually equipment datasheets, a site plan showing the new/existing equipment location, and a one-page description of the work. For most replacements, you can submit online via the Lomita permit portal (search 'Lomita CA building permit portal' to confirm the current URL, as it may have changed). Once submitted, expect 5-10 days for review, then you'll either get a permit or a request for revisions. Hire a licensed HVAC contractor or electrician for the electrical portions if you're doing this as an owner-builder. Schedule inspections through the permit portal or by calling the building department. Rough-in inspection happens after ducts/piping are in place but before final connections; final inspection happens when the system is running and thermostat controls are verified. Total timeline from permit submission to final sign-off: 2-3 weeks for straightforward replacements, 4-6 weeks if revisions are requested or ductwork is modified.

Three Lomita hvac scenarios

Scenario A
Like-for-like furnace replacement, 1970s home, coastal Lomita (3B climate zone), no ductwork changes
You're replacing a 40-year-old furnace with a new 80,000 BTU unit of the same capacity, keeping ducts in place, in a coastal Lomita residence. This absolutely requires a permit. The City of Lomita Building Department will ask for the old furnace nameplate specs (or your estimate of capacity), the new unit model number and BTU rating, and a one-page summary stating 'replacement only, no ductwork modifications.' Because you're in the coastal 3B zone, ductwork insulation must be R-6 minimum; if your existing ducts are bare or older low-R wrap, Lomita's inspector will flag this during rough-in inspection and require you to upgrade insulation to R-6 (typically $1,500–$3,000 in labor and materials to wrap existing runs). If you're an owner-builder, you can do the furnace removal/installation yourself, but a licensed C-10 electrician must handle the thermostat wiring and the 240-volt disconnect switch (budget $800–$1,200 for electrician time). The permit fee will be roughly $100–$150 based on a $5,000–$6,000 total project cost (equipment + labor). Plan review takes 5-7 business days; rough-in inspection (ducts/piping before connection) happens within 48 hours of your call; final inspection (furnace running, controls operational) follows 1-2 days after completion. Total timeline: 2-3 weeks from permit submission to final sign-off. The city will not close the permit until the system is on, operating at proper temperatures, and the thermostat is responding correctly.
Permit required | Ductwork insulation upgrade likely (R-6 coastal minimum) | Licensed electrician required for disconnect/thermostat | Permit fee $100–$150 | Electrician $800–$1,200 | Ductwork wrap $1,500–$3,000 (if needed) | Total project cost $6,500–$10,000 | 2-3 weeks to final sign-off
Scenario B
New air conditioning system added to existing furnace, foothills Lomita (5B climate zone), ductwork redesign required
You have a heating-only furnace in a 1980s foothills home (5B climate zone) and want to add a 3-ton AC system. Because this involves new refrigerant piping, a new condensing unit outside, and likely ductwork modifications (adding return-air ducts or relocating supply ducts for balanced airflow), Lomita requires a full mechanical permit. The complexity here is that you're in the 5B mountain zone, so Title 24 requires R-8 ductwork insulation, not the R-6 of coastal areas; Lomita's inspector will catch this and require upgraded wrap on all supply ducts in unconditioned spaces (attic, crawlspace). You'll also need an ACCA Manual J load calculation to prove the existing furnace's airflow (CFM rating) is adequate for the new AC coil — if it isn't, you may need to upsize or reposition ducts. This work almost certainly requires a licensed HVAC contractor (not just an owner-builder doing a swap) because refrigerant handling requires EPA Section 608 certification, and new ductwork installation requires HVAC knowledge. The permit fee will be higher: $250–$400 based on an estimated $10,000–$15,000 project (AC equipment + labor + ductwork). Plan review includes a full mechanical engineer review if ductwork is being redesigned significantly, which can add 7-10 days to the process. You'll need two inspections: a rough-in (refrigerant lines, ductwork, thermostat wiring before connections are sealed) and a final (system operational, temperature differential verified, refrigerant charge confirmed). Because this is a licensed contractor job, the contractor will typically handle permit intake and inspections — you just coordinate timing and access. Total timeline: 3-4 weeks from permit submission to final sign-off, assuming no plan review rejections.
Permit required (new AC system) | Load calculation (Manual J) required | Ductwork insulation R-8 minimum (foothills 5B zone) | Licensed HVAC contractor required | Permit fee $250–$400 | Project cost $10,000–$15,000 | Rough-in + final inspections | EPA 608 certification required | 3-4 weeks to completion
Scenario C
Thermostat upgrade to smart programmable unit, existing furnace/AC unchanged, owner-builder pull
You want to swap out an old manual thermostat for a new smart (WiFi-enabled) programmable thermostat on an existing furnace-AC system, no equipment changes, no ductwork work. This is the most ambiguous scenario. Lomita's building code technically does not require a permit for 'thermostat replacement only' if you're simply swapping the device in an existing wall cavity with no new wiring runs. However, if the new thermostat requires new wiring, a new 24V control transformer, or a new breaker/disconnect (some smart thermostats need dedicated power runs), then it's considered electrical work and requires a C-10 electrician and a permit. The safe play: call Lomita's building department and describe exactly what you're doing ('replacing manual thermostat, existing wiring, no new circuits'). If the department says 'no permit needed,' get that in writing (email confirmation). If they say 'new wiring = permit required,' then you'll need a permit ($50–$100 for a minor electrical permit) and a licensed electrician ($300–$600). Most smart thermostats can be wired into existing control wiring without new circuits, so a permit may not be required — but Lomita is stricter than some areas, so confirm first. If you do need a permit, as an owner-builder you cannot do the electrical yourself; a C-10 must pull the thermostat permit and do the wiring. Inspection is simple: the inspector verifies the thermostat powers on, connects to WiFi, and responds to setback commands. Timeline: 1 week if no permit needed, 2-3 weeks if a permit is required (due to electrician scheduling and inspection timing).
Permit requirement depends on wiring changes | Call Lomita Building Department to confirm scope | If new wiring required: C-10 electrician mandatory | Permit fee $50–$100 (if required) | Electrician cost $300–$600 (if required) | Smart thermostat device $150–$400 | Total $450–$1,100 (if permit required); $150–$400 (if not) | 1-3 weeks depending on permit status

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Title 24 and coastal vs. mountain HVAC rules in Lomita

Lomita's dual-zone geography (coastal 3B-3C and foothills 5B-6B) creates two different Title 24 energy compliance paths for HVAC. California Title 24 Part 6 (Energy Code) specifies ductwork insulation minimums, thermostat controls, and equipment efficiency tiers based on climate zone. Coastal areas like most of Lomita (3B-3C) are mild-climate zones with lower heating/cooling demands, so minimum duct insulation is R-6 in unconditioned spaces; foothills areas (5B-6B) are more severe, requiring R-8 in some configurations. Lomita's building department assigns your property to a zone based on its latitude and elevation using the ASHRAE climate zone map, so you can't negotiate or appeal the zone assignment — it's determined by address.

This matters during permit review and inspection. When you submit an HVAC permit, Lomita's plan reviewer checks your proposed equipment efficiency (SEER/AFUE ratings) against the Title 24 minimum for your zone. Coastal properties can use slightly lower-efficiency equipment than foothills properties, which reduces upfront cost. For example, a 13 SEER air conditioner is compliant for coastal 3B but may not meet the 14 SEER minimum for foothills 5B. Similarly, ductwork insulation gets flagged: if you're replacing ductwork in a foothills property, the inspector will measure the wrap R-value and require R-8 (or equivalent thermal resistance); if you reuse existing bare ducts, you'll be ordered to wrap them. Most homeowners don't budget for duct wrapping, so this becomes a surprise cost ($1,500–$3,000 depending on duct length).

Thermostat and controls also vary by zone. Title 24 requires 'demand responsive controls' for all new HVAC systems, meaning the thermostat must have automatic setback capability (lower heating, raise cooling when unoccupied). Foothills properties with more extreme seasonal swings are often audited more closely for this requirement. Many older homes have manual or non-programmable thermostats; replacing the furnace alone doesn't trigger a mandatory thermostat upgrade, but replacing the entire system (furnace + AC + coils) may. Lomita inspectors sometimes ask for evidence of a programmable or smart thermostat during final inspection if the project was extensive enough. A Title 24-compliant smart thermostat costs $150–$400 and should be factored into any system-wide replacement estimate.

Owner-builder HVAC permits and the electrician carve-out

California Business & Professions Code § 7044 permits an owner-builder to pull and perform mechanical permits without a contractor license — but only for work on their own, owner-occupied property. Lomita honors this state law, meaning you can theoretically pull your own HVAC permit, buy the furnace, and install it yourself. However, § 7047 immediately carves out electrical work: no unlicensed person, including owner-builders, may perform electrical work in California. This means the thermostat wiring, the 240-volt disconnect switch, the breaker connection, and any control voltage wiring must be done by a licensed C-10 electrician, even if you're the owner-builder doing the mechanical swap.

In practice, this creates a split-trade situation that frustrates many owner-builders. You pull the mechanical permit, hire the C-10 for the electrical portions, and coordinate timing. The electrician will likely want to pull a separate electrical permit (or piggyback on your mechanical permit) for their work. Lomita's building department will not sign off on your mechanical permit until the electrical rough-in (thermostat wiring, disconnect switch installation) has been inspected by the city's electrical inspector. This means you can't just do the furnace swap and call for mechanical inspection; the electrical work must be completed and inspected first. Most owner-builders find it simpler and less stressful to hire a licensed HVAC contractor who holds both mechanical and electrical credentials, avoiding the split-trade headache entirely.

The cost delta between owner-builder and contractor is roughly 40-60% of labor. If a contractor charges $3,000 labor for a furnace replacement, the owner-builder saves $1,200–$1,800 by doing the swap themselves — but then spends $800–$1,200 on the electrician, netting a savings of $400–$600. Smaller savings once you account for permit fees, inspection delays, and the risk of code violations that trigger rework. For complex jobs (adding AC to heating-only, ductwork redesign, refrigerant piping), the contractor route is almost always more economical and faster, since they're familiar with Lomita's plan review quirks and can get changes right the first time.

City of Lomita Building Department
Lomita City Hall, Lomita, California (contact city hall main line for building department extension)
Phone: Search 'Lomita CA building department phone' or call Lomita City Hall main line | Lomita permit portal (search 'Lomita CA building permit online' to confirm current URL; portal access and features vary)
Monday–Friday, 8 AM – 5 PM (verify locally, hours may vary seasonally)

Common questions

Do I need a permit to replace my furnace with the exact same model?

Yes. Lomita requires a permit for any furnace replacement, even if you're installing identical equipment in the same location. The city treats replacement as a modification to a mechanical system, and all mechanical system work requires a permit under the California Mechanical Code. The only exception is if your furnace is 'beyond economical repair' and you replace it with exact specs and no ductwork changes — but you still must pull the permit; you just won't need as extensive a plan review. Call the building department with your old and new equipment specs to confirm the permit scope.

Can I do the HVAC work myself as an owner-builder in Lomita?

You can pull the mechanical permit and perform the physical furnace/AC swap yourself under California Business & Professions Code § 7044. However, all electrical work (thermostat wiring, disconnect switch, breaker connection) must be done by a licensed C-10 electrician — you cannot do this yourself, even as the owner-builder. Expect to pay the electrician $800–$1,200 for their portion. Most owner-builders find it simpler to hire a licensed HVAC contractor for the entire job rather than coordinate two trades.

What's the difference between coastal and foothills HVAC rules in Lomita?

Lomita spans two climate zones: coastal (3B-3C) and foothills (5B-6B). Title 24 sets different ductwork insulation minimums: R-6 for coastal, R-8 for foothills. Coastal properties can use slightly lower-efficiency equipment. Foothills properties are often audited more closely for thermostat controls and setback capability. Lomita's building department assigns your zone by address; you cannot change it. When you submit a permit, the reviewer will check your equipment and ductwork against the rules for your zone.

Do I need an electrician for a smart thermostat upgrade?

Only if the new thermostat requires new wiring or a dedicated circuit. If you're swapping a smart thermostat into an existing wall cavity with existing control wiring, you may not need a permit or electrician. However, call Lomita's building department first to describe your exact plan — some smart thermostats need new 24V transformer wiring, which requires a C-10 electrician and a permit. Get the department's answer in writing (email) to protect yourself.

How much will my HVAC permit cost in Lomita?

HVAC permit fees are calculated as a percentage of estimated project cost, typically 1.5-2%. A $5,000 furnace replacement generates a $75–$100 permit fee. A $12,000 AC system with ductwork modifications is $180–$240. Add the cost of inspections (usually bundled into the permit, no separate fee). Plan review takes 5-10 business days for standard replacements; if ductwork is redesigned, 7-14 days. Electrician work is separate from the permit fee.

What if I install HVAC without a permit in Lomita?

If discovered, Lomita can issue a stop-work order (fines $500–$2,000), force you to hire a licensed contractor to pull permits retroactively and pass inspection, and block refinancing or home sales until the work is permitted and inspected. Insurance may also deny claims if an unpermitted system fails and damages your home. Disclosure requirements on resale mean you'll have to tell buyers about unpermitted HVAC work, which typically triggers a demand to permit and inspect before closing or a price reduction of $5,000–$15,000.

Do I need a load calculation (Manual J) for my HVAC replacement?

Not for like-for-like replacements of the same capacity in the same location. However, if you're upgrading to a larger capacity, adding AC to a heating-only system, or significantly modifying ductwork, Lomita will ask for an ACCA Manual J load calculation to verify the system is properly sized. This typically costs $200–$400 and is performed by an HVAC contractor or engineer. If you don't provide one, the permit may be held pending review.

What's required for the rough-in and final inspection?

Rough-in inspection verifies that ductwork, refrigerant piping, and thermostat wiring are in place but not yet sealed or connected. The inspector checks duct insulation R-values (R-6 coastal, R-8 foothills), verifies no leaks in piping, and confirms wiring connections. Final inspection happens when the system is running: the inspector verifies temperature differential (furnace heating, AC cooling to spec), thermostat responds to setback commands, and all controls function. Both inspections are scheduled by calling the building department or via the permit portal; schedule rough-in after ductwork/piping are complete, final after startup.

Can I use an unlicensed contractor to save money on HVAC in Lomita?

No. California law and Lomita code require all HVAC work to be done by a licensed contractor (A, B, or C-20 license for HVAC). Exceptions exist only for owner-builders performing work on their own property, and even then, electrical work must be done by a C-10. Using an unlicensed contractor voids the permit, risks stop-work orders, creates insurance and resale liability, and means the contractor has no legal recourse if the work fails. Always verify contractor licenses with the California Department of Consumer Affairs.

How long does the entire HVAC permit process take in Lomita?

For a straightforward furnace replacement: 2-3 weeks total. For a system upgrade (adding AC, ductwork redesign): 3-4 weeks. Timeline: 5-10 days plan review, 48 hours from your call to rough-in inspection, 1-2 days after completion to final inspection. If the city requests revisions (e.g., 'upgrade duct insulation'), add 3-5 days. If a mechanical engineer review is needed, add 7-10 days. Complex projects (whole-home retrofit, new zones, major ductwork) can stretch to 5-6 weeks. Schedule electrician work early to avoid delays in the electrical rough-in.

Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current hvac permit requirements with the City of Lomita Building Department before starting your project.

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