ADU Builder in Lancaster, CA: Local Rules, Costs and Permits

How much does it cost to build an ADU in Lancaster, CA?

L Square publishes configured prefab model prices that run from $180,000 for the 600 sq ft Model 600 to $354,000 for the 1,200 sq ft Model 1200, with Models 800A and 800B at $240,000 each and Models 1000A and 1000B at $295,000 each. Those are model prices, not a quote for your lot, so site work, utility routing, permits and finish selections need a property-specific proposal. On the city side, the Building Fee Schedule and the Citywide Fee Schedule both took effect 10-01-2026, and the 2021 Development Impact Fee Schedule is the document that applies to development projects. State law keeps impact fees off the smallest units: no impact fee for an accessory dwelling unit of 750 square feet of interior livable space or less, and impact fees on a larger unit are charged in proportion to the square footage of the primary dwelling.

How long does an ADU permit take in Lancaster?

Lancaster routes ADU plans through its Building and Safety Division, and the city states that ADUs do not need Planning approval, so an application goes straight to Permitting. Applications are filed online through the city's Accela Citizen Access portal. Plan check engineers issue a correction list after the first review and the returned plans get a second review, and the city says the first plan check is usually complete within three weeks. The state sets the outer clock: written notice of completeness within 15 business days, a decision within 60 days, and a complete application the city does not act on in that window is deemed approved. State law also requires ministerial review with no hearing. Submittals need one complete PDF set of plans with a fully dimensioned site plan, floor plans, elevations, sections and structural calculations wet stamped by a licensed engineer or architect, and the city routes plans to its Community Development Department and Utility Services Division while you make a separate submittal to the Los Angeles County Fire Department.

What are the ADU rules for a detached unit in Lancaster?

State law is the floor your city has to meet. The total floor area of a detached accessory dwelling unit cannot exceed 1,200 square feet, an attached unit cannot exceed 50 percent of the existing primary dwelling, and a new detached unit needs a side and rear yard setback of no more than four feet. A city cannot cap size below 850 square feet of interior livable space, or 1,000 square feet when the unit has more than one bedroom, and it cannot enforce a height limit that refuses 16 feet for a detached unit on a lot with an existing single family or multifamily dwelling, or 18 feet when the lot is within one-half of one mile walking distance of a major transit stop. Local design values matter in the high desert: the city's plan check page lists basic wind speed Exposure C with Risk Category I at 90 mph, roof live load 20 psf and California Climate Zone 14. Parking rules come from state law too, capped at one space per unit or per bedroom, whichever is less, with no replacement parking required when an existing garage or carport is converted.

Does the city of Lancaster have pre-approved ADU plans?

The City of Lancaster offers a selection of pre-approved ADU plans designed by the architectural firm RRM Design Group, with five designs named Poppy, Juniper, Goldenbrush, Primrose and Sunflower, each available in either a California Ranch or Mediterranean architectural style. You buy the plans through the Accela Citizen Access portal run by the Building and Safety Division, and each package includes most of the design documents the permit application needs. A project-specific site plan is still required for each application, and the city also wants its own ADU Application and Minimum Plan Submittal Requirements on file. The ADU Assistance Loan Program can cover the purchase price: it offers up to $10,000 in a deferred-payment, no-interest loan for soft costs with no monthly payments, possible forgiveness over five years, and rules that require you to keep owner occupancy and rent the unit to a low-income household for at least five years. Published elevations for those plans run from Poppy at 350 sf plus a 70 sf porch and 11 feet 9 inches tall to Primrose at 840 sf plus an 85 sf porch and 14 feet, with a 16-foot maximum shown on each.

What should I check before building an ADU on a Lancaster lot?

Check the property and the paperwork before you draw anything. Zoning for your address or APN sits in the city's Lancaster Data Parcel Viewer, and the plan check page requires a fully dimensioned site plan that shows easements, lot area, setbacks, floor area ratio and lot coverage tabulations, and the locations of utility meters, sewer connections and fire hydrants. The city's structural requirements call for the soil type and bearing value on the plans, and a soil or geotechnical report may be required where expansive soils exist. Separate electrical, mechanical and plumbing permits can be pulled on their own, and shoring plans may be needed for excavations that exceed four feet in depth. On the building side, L Square holds CSLB #1095476 and publishes configured prefab model prices from $180,000 to $354,000 that are the starting point for a written proposal, not the final project total.

Official Lancaster ADU sources

• The city's Pre-approved ADU Plans page states that the City of Lancaster offers pre-approved ADU plans designed by the architectural firm RRM Design Group, that homeowners can choose from five designs named Poppy, Juniper, Goldenbrush, Primrose and Sunflower, each available in either a California Ranch or Mediterranean architectural style, that plans are purchased on the Accela Citizen Access portal through the city's Building and Safety Division, and that a project-specific site plan is still required for each application. Official source
• The city's ADU Assistance Loan Program page states that the program offers up to $10,000 in a deferred-payment, no-interest loan to cover soft costs, that there are no monthly payments, that the loan may be forgiven over five years if certain conditions are met, and that borrowers must maintain owner-occupancy, rent the ADU to a low-income household and keep the ADU affordable for at least five years. The same page lists pre-approved plan elevations: Poppy at 350 sf, Juniper at 602 sf, Goldenbrush at 799 sf and Primrose at 840 sf, each with a 16-foot maximum. Official source
• The city's Planning FAQs page states that ADUs do not require Planning approval and can proceed directly to Permitting, and that owner-builder ADU applications require the property owner to reside onsite. The page also states that Planning reviews are processed digitally, that over-the-counter reviews are typically processed within a couple of days, and that zoning information is displayed in the Lancaster Data Parcel Viewer App. Official source
• The city's Permits page states that permit applications are filed online through the city's Accela Citizen Access portal, that permits must be obtained prior to commencing any work and may also require building plans, and that effective January 1, 2026 the City of Lancaster adopts the 2025 California Building Code, so all new plan submittals must be designed per the 2025 Codes. Official source
• The city's Fee Schedules and Forms page lists an ADU Application that is required for all ADU submittals, the ADU Minimum Plan Submittal Requirements, a Building Fee Schedule effective 10-01-2026, a Citywide Fee Schedule effective 10-01-2026, the 2021 Development Impact Fee Schedule, and the 2025 Lancaster Building Code Amendments (Ord. 1139). Official source
• The city's Plan Check page states that plans are reviewed by plan check engineers who issue a correction list and then review the returned plans a second time, that the first plan check is usually complete within three weeks, that plans are routed to the Community Development Department and the Utility Services Division, and that a separate submittal to the Los Angeles County Fire Department is required. The page also lists local structural design values: basic wind speed Exposure C with Risk Category I at 90 mph, roof live load 20 psf and California Climate Zone 14. Official source
• California Government Code Section 66314 provides that parking requirements for accessory dwelling units shall not exceed one parking space per unit or per bedroom, whichever is less, that a local agency shall not require replacement parking spaces when a garage, carport, covered parking structure or uncovered parking space is demolished with an accessory dwelling unit or converted to one, that the total floor area of a detached accessory dwelling unit shall not exceed 1,200 square feet, and that an attached accessory dwelling unit shall not exceed 50 percent of the existing primary dwelling. Official source
• California Government Code Section 66317 provides that a permitting agency must give written notice of whether an accessory dwelling unit application is complete no later than 15 business days after receiving it, must approve or deny a completed application within 60 days, treats a completed application the agency has not acted on in that time as approved, and requires that an accessory dwelling unit application be considered and approved ministerially without discretionary review or a hearing. Official source
• California Government Code Section 66311.5 provides that a local agency, special district or water corporation shall not impose any impact fee upon the development of an accessory dwelling unit that has 750 square feet of interior livable space or less, and that any impact fee charged for a larger accessory dwelling unit is charged proportionately in relation to the square footage of the primary dwelling unit. Official source
• California Government Code Section 66321 provides that a local agency shall not establish a maximum square footage requirement for an attached or detached accessory dwelling unit that is less than eight hundred fifty square feet of interior livable space, or one thousand square feet for an accessory dwelling unit that provides more than one bedroom, and that a local agency shall not enforce any height limitation that does not allow at least 16 feet for a detached accessory dwelling unit on a lot with an existing or proposed single family or multifamily dwelling unit. Official source
• The California Department of Housing and Community Development letter on the City of Lancaster adopted 2021-2029 Housing Element states that Program H-1.5 commits the city to update its ADU ordinance to comply with State law, to remove regulations that are not compliant with State law including parking requirements that do not comply with State law, to create a process to bring unpermitted ADUs up to code, to identify an ADU specialist within the Community Development Division, and to monitor ADU permit applications, with a quantified objective of 332 ADUs during the planning period. Official source