What happens if you skip the permit (and you needed one)
- Building inspector files a stop-work order, halts construction mid-frame, and the City can issue a citation carrying $200–$1,000 per violation per day until permit is pulled retroactively.
- Homeowners insurance may deny claims for unpermitted work, leaving you uninsured for fire/injury liability on the ADU — especially damaging if a renter is injured.
- Unpermitted ADU triggers mandatory disclosure when selling the home; buyer's lender will likely refuse to fund until the unit is either removed or permitted retroactively (costly and time-consuming).
- Cerritos Planning Division may initiate code enforcement; fines escalate to $500–$1,500 per violation, and removal of the entire unit can be mandated if the violation is deemed safety-related (electrical, fire egress, structural).
Cerritos ADU permits — the key details
California Government Code 65852.2 and AB 68/881 mandate that cities like Cerritos allow ADUs, but the state law does not override all local controls. Cerritos permits two ADUs per single-family lot (one detached, one junior ADU, or two junior ADUs) as of 2022. The City still enforces setback rules: detached ADUs typically require a rear setback of 5-15 feet (depending on lot size and zoning) and side setbacks of 5-10 feet. An ADU cannot exceed 800 sq ft if detached or above-garage; junior ADUs (kitchen in main house, sleeping/bathroom in accessory structure) can be up to 500 sq ft. Garage conversions and junior ADUs are treated more leniently on setbacks because they reuse existing structures. A key Cerritos-specific rule: the city has not adopted a blanket parking exemption for ADUs, so applicants must either provide 1 on-site parking space (or 0.5 spaces for transit-rich areas — very limited in Cerritos) or file a variance application. This parking requirement adds 4-8 weeks and $3,000–$5,000 to your timeline and cost. Plan sets for ADUs must include site plan, floor plans, elevations, electrical one-line diagram, plumbing isometric, and foundation/framing details if detached. If the ADU will have separate utility connections (as opposed to a sub-meter off the main panel), both the water meter and electrical service must be shown on the site plan with utility company pre-approval letters.
Egress and fire safety are non-negotiable. IRC R310 and California Title 24 require all ADU bedrooms to have egress windows or doors meeting minimum dimensions (typically 36 inches wide, 43 inches tall, with a 5.7 sq ft minimum opening for a basement, or 5 sq ft for above-grade bedrooms). In a garage conversion, this often forces a window reframe or new door addition. Hallways to the main exit must be at least 36 inches wide; bedrooms at least 70 sq ft. Ceiling height in habitable rooms must be 7 feet, 0 inches minimum (7 feet 6 inches in kitchens and bathrooms). Cerritos fire marshal review is mandatory and typically takes 2-3 weeks; if sprinklers are triggered (usually when total structures on the lot exceed 5,000 sq ft or when ADU square footage pushes the lot to a certain density), a full sprinkler plan is required, adding $8,000–$15,000 in materials and design. Most detached ADUs in Cerritos do not trigger sprinklers, but garage conversions that increase square footage significantly may.
Utility infrastructure is often a hidden cost driver in Cerritos. If your lot is serviced by a small water line (e.g., 3/4-inch main), adding an ADU with a separate meter may require a 1-inch main upgrade at the street, costing $5,000–$15,000 depending on the distance from the meter. Electrical service is easier: if your main panel has room for a 50-amp sub-panel or a new ADU breaker, the cost is $1,500–$3,000. If a main service upgrade is needed (from 100 amps to 150 amps or 200 amps), costs spike to $3,000–$8,000. Septic systems are NOT used in Cerritos (city sewer service is available citywide); the ADU will connect to the existing main line, so no septic sizing is an issue. However, if the existing sewer line is old (pre-1980s) or undersized, the City may require a sewer capacity study or line upsizing, adding $2,000–$6,000. Confirm with the City of Cerritos Public Works Department (not the Building Department) whether a sewer study is needed for your lot before finalizing your plan set.
Owner-builder status is allowed in California for ADU projects under Business and Professions Code § 7044, but you cannot pull electrical or plumbing permits yourself — those trades require a licensed contractor. This is a common misconception: you can be the general contractor (and do framing, drywall, finishing), but you must hire a licensed electrician (C-10 or C-10/A license) and a licensed plumber (A license) to pull those trades and sign off. Many homeowners hire a general contractor instead to manage all subcontractors; GC fees are typically 15-25% of the project cost. The permit application itself is filed by the property owner, architect, or a contractor; the City of Cerritos Building Department requires a completed application form, a proof of property ownership (deed or current tax bill), and plan sets. Turnaround for an initial completeness review is 5-10 working days; if there are plan deficiencies, the City issues a revision request (typically a 15-day turnaround for resubmission). Once the application is deemed complete, the 60-day AB 671 clock starts; however, plan review, fire marshal sign-off, and utility company letters can extend the timeline to 75-90 days in practice. Inspection scheduling begins once the permit is issued; building inspections (foundation, framing, rough trades, insulation, drywall, final) are typically 5-7 inspections over 8-12 weeks of construction.
Cerritos does not have a dedicated ADU webpage or pre-approved plan library as of 2024, so most applicants rely on private architects or plan services (e.g., Design AVA, Blueprint ADU). The City's general building permit portal (if available) may not have an ADU-specific track; email or call the Building Department to confirm the current application process and fee schedule. ADU permit fees in Cerritos are typically based on valuation: a $150,000 ADU project would incur permit fees of $600–$900 (0.4-0.6% of valuation) plus plan review fees ($300–$500) and sometimes an ADU-specific processing fee ($250–$500). Total soft costs (permits, review, engineering) typically range $2,500–$4,500 for a straightforward project, and $5,000–$8,000 if parking variance, sewer study, or utility upgrades are required. Construction timeline for a 600-sq-ft detached ADU is 12-16 weeks; for a garage conversion, 8-12 weeks. Financing ADUs can be tricky: conventional mortgages (Fannie Mae, Freddie Mac) now allow ADU rents as income on the primary mortgage, but the property must be fully permitted and the ADU rental-ready at closing. Some lenders require the ADU to be completed before the primary loan funds; others allow completion during the loan term if escrowed funds are held. Check with your lender early — waiting until after permit approval to clarify financing can derail a project timeline.
Three Cerritos accessory dwelling unit (adu) scenarios
Parking and variance timing in Cerritos: the hidden cost of ADU projects
Cerritos Building Department has not adopted a blanket ADU parking exemption, unlike some LA County neighbors. State law (Government Code 65852.2) does not mandate parking elimination, so Cerritos retains the right to enforce its zoning code parking requirements: typically 1 space per ADU in residential zones. If your lot is too small or awkwardly shaped to provide an on-site space, you must file a parking variance application through the Planning Department, which is separate from the building permit process. A variance request triggers a public hearing (or staff-level approval in some cases, depending on Cerritos' threshold), which adds 6-12 weeks and $2,000–$5,000 in application fees, traffic study (if required), and engineering. Many homeowners avoid the variance by squeezing a parking pad somewhere on the lot: a minimum 9-foot-wide x 18-foot-deep pad is sufficient (162 sq ft), which fits on most rear yards if the ADU is positioned correctly. Alternatively, some homeowners convert part of the driveway or front yard to a dedicated pull-in space. The cheaper move is to provide the space upfront during ADU design, not later as a variance add-on.
If your lot backs onto a public alley or street with unrestricted parking, Cerritos may accept a letter from the City stating that public parking is available and accessible within 100-150 feet of your lot, which can satisfy the parking requirement without an on-site space (a workaround). However, this requires explicit sign-off from the Cerritos Planning Division and is not guaranteed. Never assume public parking will satisfy the requirement; email the City's ADU coordinator (if one is designated) or the Planning Department to confirm before you finalize your design. Delaying this clarification to the permit-ready phase is expensive.
Another variance scenario: if Cerritos has adopted any ADU-specific parking flexibility (e.g., 0.5 spaces for small units under 500 sq ft, or exemption for carshare-accessible lots), the planning staff will mention it in their initial consultation. As of 2024, Cerritos' website does not highlight an ADU parking exemption, so assume 1 space is required unless staff tells you otherwise in writing. Keep all communications (emails, phone notes with timestamps) to protect yourself if a parking requirement is later disputed during inspection or final sign-off.
Utility infrastructure and sewer capacity: Cerritos-specific costs
Cerritos is fully served by city water and sewer (no septic systems). However, many older Cerritos homes (pre-1970) are connected to small-diameter water mains (0.75 inch) and old cast-iron or Orangeburg sewer lines that may not have been upgraded for density. When you apply for an ADU permit, the City's Public Works Department is copied on the permit application and may issue a 'condition of approval' requiring a sewer capacity study or line video inspection. A sewer line camera inspection costs $400–$800; if the line is in poor condition (cracks, roots, bellies), the City may mandate a sewer-line repair or replacement, which is expensive: $5,000–$15,000 for a residential line (depending on depth and distance). Avoid surprise costs by contacting Public Works early (before finalizing your plan set) and asking whether a sewer study is needed for your address. If the line is old, budget conservatively.
Water service is often the other constraint. Many Cerritos blocks are served by 0.75-inch or 1-inch mains; if your existing home has a 0.75-inch meter and service line, adding an ADU with a separate meter may require the city to upsize the main line at the street. This is a rare trigger for residential projects, but if your lot is at the end of a main or in a pressure-constrained area, Water Works (the Cerritos water provider) may flag it. A main-line upsizing can cost $5,000–$15,000 and can take 4-8 weeks for the utility to complete. Again, proactive contact with Water Works (get the parcel number and ask whether a main-line study is needed for a new ADU meter) saves money and time.
Electrical service upgrade is less common but still possible. If your home has 100-amp service and the electrical panel is full, adding a sub-panel for an ADU is straightforward (add a 50-amp or 60-amp breaker in the main panel, or run a new sub-panel, cost $1,500–$3,000). If your panel is oversized, a single new breaker costs $300–$500. However, if you want the ADU to have a fully separate electrical service (disconnected from the main panel), you need a second meter from the utility company, which requires a second service entrance on the exterior wall (costs $3,000–$8,000 depending on distance from the utility line). Most ADU projects use a sub-panel to avoid the cost and complexity of a second service. During the design phase, hire an electrician to inspect your main panel and confirm capacity; if a full service upgrade is needed, your ADU project cost could increase by $5,000–$10,000.
Cerritos City Hall, 18125 Bloomfield Avenue, Cerritos, CA 90703 (confirmed via city website; call to verify specific suite or department floor)
Phone: (562) 916-1254 or Building Department direct line (check cerritos.us for current number) | Check cerritos.us for online permit portal; if not available, permits are submitted in person at City Hall or via mail with a cover letter
Monday–Friday, 8:00 AM–5:00 PM (typical; confirm on cerritos.us)
Common questions
Can I build two ADUs on my Cerritos lot?
Yes, California AB 68 (effective 2021) allows up to two ADUs per lot in most jurisdictions, including Cerritos. You can build one detached ADU and one junior ADU, or two junior ADUs, as long as they comply with state size limits (800 sq ft for detached/above-garage, 500 sq ft for junior) and local setback rules. However, both require separate building permits, and Cerritos will enforce parking (1 space per ADU, unless a variance is granted). Confirm with the City's Planning Division that your lot size supports two ADUs without triggering lot-split rules or density limits. Email or call the Building Department before investing in two ADU plans.
Do I need a separate electrical service meter for my ADU, or can I sub-meter off my main panel?
You can use a sub-meter or a new breaker in your existing main panel if your panel has capacity. A sub-meter off the main panel is the standard approach (cost $800–$1,500 for materials and installation). If your main panel is full or oversized, upgrading to 150 amps or 200 amps is an option but costly ($3,000–$8,000). A fully separate electrical service (second meter from the utility) is optional and expensive ($3,000–$8,000) and is only required if you want to disconnect the ADU from the main house entirely. Most Cerritos homeowners choose sub-metering to avoid utility upgrade costs.
How long does a Cerritos ADU permit take from application to permit issuance?
The state-mandated 60-day clock (AB 671) starts once your application is deemed complete. However, initial completeness review takes 5-10 working days, plan review and fire marshal review take 40-50 days, and utility company pre-approvals add 1-2 weeks. In practice, expect 60-90 days from submission to permit issuance. Garage conversions are faster (45-60 days) because there is no new foundation review. Incomplete applications reset the clock, so submit a thorough plan set the first time.
Do I need to hire an architect or engineer for my ADU plans, or can I use a template?
Cerritos requires plan sets sealed by a licensed California architect or engineer (stamp required on all sheets) for any ADU project. You cannot use a generic template from the internet without professional review. However, pre-approved ADU plans (sold by companies like Design AVA, Blueprint ADU, or Plan Graphics) include architect-sealed sheets; you customize them with your lot dimensions and then have a local architect do a final review and sign-off (typically $1,000–$2,000 for this limited review). This is cheaper than hiring an architect to design from scratch ($3,000–$6,000). For structural changes (above-garage, foundation retrofit), a structural engineer is required in addition to the architect.
Is an owner-builder allowed for an ADU in Cerritos?
Yes, California Business and Professions Code § 7044 allows an owner-builder to pull permits and act as the general contractor on an ADU. However, you cannot pull electrical or plumbing permits yourself — those trades require a licensed electrician (C-10 license) and a licensed plumber (A license). You can do framing, drywall, finishing, painting, and other non-licensed work. Many owner-builders hire a GC to manage subcontractors instead, paying 15-25% of construction cost for their coordination and liability insurance.
What happens if my ADU plans are rejected or require major revisions?
If the City issues a revision request, you have 15 days to resubmit; the 60-day AB 671 timeline pauses during the revision period and restarts when you resubmit. Major revisions (e.g., setback conflict requiring a redesign, egress failure) can extend the permit timeline to 90-120+ days. Common rejection reasons: setback violation, parking not addressed, egress window dimensions wrong, utility coordination missing, or fire marshal safety concern. Avoid rejections by having a local architect or engineer review your plans against Cerritos code before you submit.
Will my ADU rental income affect my property taxes in California?
ADU rental income does not trigger a reassessment of your home's property value for property-tax purposes under Proposition 13 (California Code § 402). However, the ADU structure itself may be valued separately and assessed as a new improvement; you will receive a supplemental property tax bill for the ADU's value (typically 0.125% of the structure's cost basis, plus local assessments). Consult a property tax accountant or the Los Angeles County Assessor's office for specifics. Rental income is taxable federal income but does not increase your home's Prop 13 base year value.
Can a non-owner occupant (e.g., an investor or corporation) own an ADU in Cerritos?
California state law eliminated owner-occupancy requirements for ADUs as of 2021 (AB 68). Investors, LLCs, and corporations can now own and rent ADUs without living on the property. Cerritos has adopted this state allowance, so you are not required to live in the main house or the ADU. However, some HOAs may have deed restrictions that require owner-occupancy; check your CC&Rs if your property is in an HOA. For non-owner scenarios (investor purchase), lenders may have tighter financing rules (jumbo rates, lower LTV, higher down payment), so confirm with your lender early.
Do I need a separate homeowners insurance policy for the ADU, and does it affect my mortgage?
Yes, you should add the ADU structure and contents to your homeowners insurance and notify your insurer that the ADU is being rented. Most insurers include the ADU in your primary homeowners policy if it is a single-building coverage scenario; however, rental liability (if a tenant is injured) may require an endorsement or a separate umbrella policy. Permitted ADUs are easier to insure; unpermitted ADUs may be excluded or result in policy cancellation. On the mortgage side, fannie Mae and Freddie Mac now allow ADU rental income to count toward your debt-to-income ratio on a primary mortgage refinance or purchase, which can be a financial benefit. Speak with your mortgage lender and insurance agent together to confirm coverage and qualification.
What is the Cerritos parking requirement for ADUs, and can it be waived?
Cerritos requires 1 on-site parking space per ADU (per standard zoning code). Parking is NOT automatically waived for small or transit-accessible ADUs, unlike in some LA County cities (Torrance, Manhattan Beach). If your lot cannot accommodate a parking space, you must file a parking variance with the Cerritos Planning Department, which takes 6-12 weeks and costs $2,000–$5,000. The variance requires a showing that parking is not needed (e.g., public parking is readily available and accessible within 100-150 feet). Provide an on-site pad if possible to avoid the variance delay; a minimum 9-foot-wide x 18-foot-deep space (162 sq ft) is sufficient and fits in most rear yards if the ADU is positioned correctly.