Building an ADU in Westminster
Westminster homeowners can add an ADU with help from a city program most nearby cities don’t offer: a pre-approved standard plan that cuts down on design work. Lamarc Prime Builders builds ADUs for Westminster families who want a place for parents, adult children, or a long-term renter, using either the city’s standard plan or a fully custom design. We check your lot against Westminster’s rules on height, setbacks, and spacing between buildings, then handle the permits and construction from start to finish.
ADU Services Available in Westminster, CA
Our ADU services in Westminster are designed to help homeowners move through planning, permits, and construction with fewer obstacles. We focus on understanding site conditions and local requirements early, so design decisions and approvals stay aligned from the start.
✅ 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 helps clarify what’s allowed and how to move forward efficiently.
ADU Rules in Westminster
ADUs allowed per lot
1 ADU + 1 JADU on a lot with a single-family home
Max detached ADU size
Up to 1,200 sq ft
Max attached ADU size
We confirm for your lot
Max JADU size
Up to 500 sq ft
Max height (detached)
16 ft
Two-story ADU
One story for new ADUs on a lot with an existing home
Setbacks
4 ft side and rear
Space between buildings
6 ft from the main house and other structures (10 ft from other dwellings in R2 to R5 zones)
Parking
1 space for 1+ bedrooms; none for studios, JADUs, near transit, or for conversions
Owner occupancy
Not required for an ADU; JADU requires the owner to live on site
Short-term rental (Airbnb)
31-day minimum; no Airbnb
Impact fees
None under 750 sq ft; larger ADUs pay proportionally
Pre-approved plans
Yes: city standard plan for detached ADUs (about 85% of the plan set)
Permit review
Zoning and building review during plan check; online portal or in person
Approval timeline
60 days after a complete application
Local insight
Westminster offers a pre-approved standard plan for detached ADUs that covers about 85% of the plan set. It is pre-approved, not pre-permitted, so your site-specific plans still go through plan check.
How ADU Permitting Works in Westminster
Westminster reviews ADUs against its zoning standards and the building code during plan check, and the city must decide on a complete application within 60 days under state law. Westminster accepts submittals in person or online through its Westminster Build Online Portal. For online submissions, Planning review and park fees are invoiced during plan check.
Depending on your project, you may also need separate permits, such as an addressing application, utility and sewer permits, a fire sprinkler permit, an encroachment permit, or a grading permit. Contact Westminster Planning at (714) 548-3247 or planning@westminster-ca.gov with questions.
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
Does Westminster have pre-approved ADU plans?
Yes. The city offers a standard plan for detached ADUs. It saves design time, but it is preapproved, not pre-permitted: you still need a licensed professional to prepare site-specific plans, and the project still goes through plan check.
How tall can my ADU be in Westminster?
New ADUs on a lot with an existing single-family home are limited to 16 ft and one story. An ADU attached to a new home must meet the zone’s height limit, and a second-floor portion makes all single-family standards apply.
How far does an ADU have to be from my house in Westminster?
A new detached ADU needs at least 6 ft from your main house and from other detached accessory structures. In the R2 to R5 zones, 10 ft is required from other dwelling units.
Do I need parking for an ADU in Westminster?
Often not. No parking is required for a studio, a JADU, an ADU within a half-mile walk of public transit, or an ADU that is part of the main home or an accessory structure. Otherwise one space is required, and no replacement parking is needed for a converted or demolished garage.
Can I rent my Westminster ADU on Airbnb?
No. ADUs and JADUs can’t be rented for less than 31 days. Long-term tenants and family members are fine.
Can I submit my Westminster ADU plans online?
Yes. The city accepts submittals in person or through its Westminster Build Online Portal, where you upload the required forms and plans. For the standard plan, you upload the city’s set separately from your own site plan and existing-house plans.
