Building an ADU in Placentia
Placentia’s established neighborhoods are full of detached garages, deep backyards, and homes with room to grow. Lamarc Prime Builders helps Placentia homeowners turn that space into a rental unit, a place for aging parents or adult children, or a separate guest home. Whether you are converting an existing garage or building a new detached ADU, we design the project to meet Placentia’s requirements, including its rule that an ADU match the style of your main house, and we manage it from permits to final inspection.
ADU Services Available in Placentia, CA
We help Placentia homeowners turn their ADU ideas into practical, well-planned projects. From exploring backyard development opportunities and creating functional floor plans to coordinating city approvals and managing construction, we provide guidance at every stage. Our goal is to simplify the process while delivering an ADU that complements the existing home and meets the homeowner’s needs.
✅ Detached & Attached ADUs
✅ Garage Conversion ADUs
✅ Junior ADUs (JADUs)
✅ ADU Planning & Design Coordination
✅ Permits, Plan Submittals & City Revisions
✅ Construction, Inspections & Final Completion
A free site evaluation is the best way to understand your options and plan the next steps with confidence.
ADU Rules in Placentia
ADUs allowed per lot
1 ADU + 1 JADU on a single-family lot
Max detached ADU size
Up to 1,200 sq ft
Max attached ADU size
Up to 50% of the existing home
Max JADU size
Up to 500 sq ft
Max height (detached)
16 ft (18 ft near major transit) + 2 ft for roof pitch
Two-story ADU
Attached ADUs up to 25 ft; two stories if your main house is two stories
Setbacks
4 ft side and rear; rear of the lot is the city's first choice
Space between buildings
10 ft from the main house and other structures (waived to fit an 800 sq ft unit)
Parking
1 space generally; none near transit, in historic districts, or for conversions
Owner occupancy
Generally not required for an ADU under state law
Short-term rental (Airbnb)
31-day minimum; no Airbnb
Impact fees
None under 750 sq ft; larger ADUs pay proportionally
Pre-approved plans
Program set up; no city-approved plans available yet
Permit review
Two steps: Planning (online or in person), then Building Safety plan check
Approval timeline
60 days (30 days with a pre-approved plan)
Local insight
Placentia wants an ADU to complement your home's architectural style, with the entrance not facing the street or sitting on the same side as your main entrance. The city prefers ADUs at the rear of the lot.
How ADU Permitting Works in Placentia
Placentia uses two steps. You start with the Planning Department, which you can do through the city’s online SmartGov portal or in person. Plans then go to the Building Safety Division for plan check. Your application includes a plot plan, floor plans, elevations, and landscape plans, with grading and drainage shown.
The city checks whether your application is complete within 15 business days, then must approve or deny within 60 days. If you use a plan the city has pre-approved, or one identical to a detached ADU plan approved within the current building code cycle, that drops to 30 days. If a detached garage is being replaced, the demolition permit is reviewed and issued together with the ADU permit.
Property feasibility review
Review zoning, lot conditions, access, utilities, and applicable ADU requirements.
ADU design and preparation
Prepare the site plan, architectural drawings, engineering, and required supporting documents.
City plan review and approvals
Submit the application, coordinate with city departments, and respond to plan-check corrections.
Permit issuance and construction
After approval and permit issuance, proceed with construction and required inspections.
FAQs
Can I convert my detached garage into an ADU in Placentia?
Yes. A converted garage or accessory structure keeps the setbacks it already has, and no replacement parking is required for the main house. If the garage is being replaced, the demolition permit is reviewed and issued with the ADU application.
Does my ADU have to look like my house?
Yes. Placentia requires the ADU to complement the architectural style of the main home. We select roofing, siding, and colors that tie the new unit to your existing house.
Do I need extra parking in Placentia?
Often not. No space is required within a half-mile walk of public transit, in a historic district, or when the ADU is inside existing space. No replacement parking is required when a garage is converted or demolished for the ADU.
Can I build an ADU above my garage in Placentia?
An attached ADU can be up to 25 ft and can be two stories if your main house is two stories, subject to your zone’s height limit. Detached ADUs are limited to 16 or 18 ft, which usually means one story.
Can I rent my Placentia ADU on Airbnb?
No. Rentals of the ADU must be at least 31 days. Long-term tenants and family members are fine.
Does Placentia charge impact fees on ADUs, and is financing available?
ADUs under 750 sq ft are exempt from impact fees. Larger ADUs pay fees in proportion to their size relative to the main house. The city’s ADU page also links to an affordable ADU loan program, so check it for current terms.
