ADU Builder in Monrovia, CA: Ordinance, Pre-Approved Plans and Costs

Monrovia's Pre-Approved ADU Plan Program

The City of Monrovia Community Development Department runs a Pre-Approved ADU Plan Program on the Accessory Dwelling Units page. The page states that the City is developing a catalog of pre-approved ADU plans for the public to choose from. The plans will be available to the public, but residents must work with the design professional who prepared the plan for a fee. The same page lists a Plan Submission Guide for Designers and Architects, an ADU FAQs page, and an ADU Forms and Resources page. L Square reviews the lot for setbacks, slope, utility route, and Metro Rail Station proximity before recommending a plan, then submits the application package to the Community Development Department.

Monrovia permit process and the 60 day state clock

Monrovia ADU applications go to the Community Development Department. California Government Code Section 66317(a)(2)(A) requires a completeness decision within 15 business days, and Section 66317(a)(3) gives the city 60 days to approve or deny a complete application when an existing single family home is on the lot. If the city does not act within 60 days, the application is deemed approved under state law, less any applicant requested delay. The Monrovia Accessory Dwelling Units page notes that the City updated its ADU Ordinance in February of 2025 to align with state housing legislation that took effect on January 1, 2025. L Square prepares the submittal package, schedules the intake at City Hall, and tracks both the 15 business day and 60 day clocks so the project does not slip into the next planning cycle.

Size, height, and setback rules in Monrovia

Monrovia uses the state rules for ADU size and setback under the February 2025 ordinance. California Government Code Section 66314(d)(5) caps a detached ADU on a lot with an existing or proposed primary dwelling at 1,200 square feet of floor area. Section 66321(b)(2)(A) and (B) set statewide minimum size floors of 850 square feet for a studio or one bedroom detached ADU and 1,000 square feet for a multi bedroom detached ADU, and Monrovia cannot undercut that floor. Section 66323(a)(2) creates a separate ministerial path for an 800 square foot detached ADU with 4 foot side and rear setbacks. Per the Monrovia ADU FAQs page, height is measured from the exterior finished grade, and a detached ADU may be 16 feet, 18 feet, or 20 feet depending on the lot's location and development, with greater heights available near the Metro Rail Station Major Transit Stop. State law also prohibits a front yard setback requirement for an ADU. L Square confirms the local overlay and any hillside or slope rule with the Monrovia Planning Division before final submittal.

Parking, JADU, and the maximum number of ADUs per Monrovia lot

Per the Monrovia ADU FAQs page, parking can only be required for newly constructed ADUs that are greater than 800 square feet and not within one half mile of any public transit stop, which includes any public bus stop. State law allows a maximum of three ADU types per lot, two ADUs and one JADU, regardless of the number of detached single family dwellings on the lot. A Junior ADU in Monrovia is capped at 500 square feet and is created through the conversion of living space within an existing single family home. Government Code Section 66314(d)(10) caps required parking at one space per bedroom or per unit, Section 66314(d)(11) bars the city from requiring replacement parking when a garage, carport, or covered parking structure is converted to an ADU, and Section 66314(b)(2) lets a local agency fully exempt ADUs from parking. L Square verifies the unit against current code and the local transit proximity before any close in.

Impact fees, preemption, and the California state law ceiling

Under California Government Code Section 66311.5(c)(1), Monrovia, special districts, and water corporations shall not impose any impact fee on an ADU that has 750 square feet of interior livable space or less. Any impact fees charged for an ADU larger than 750 square feet are charged proportionately in relation to the square footage of the primary dwelling. Section 66311.5(b) treats an ADU as not a new residential use for water and sewer connection fees, unless the ADU was built with a new single family home. Section 66325(a) states the ADU approval article supersedes any conflicting local ordinance, and Section 66325(b) does not authorize stricter standards than state law, only less restrictive ones. When the February 2025 Monrovia ADU Ordinance adds a rule that conflicts with state law on size, parking, setbacks, or approval timelines, state law controls. L Square confirms the local fee schedule with the Monrovia Planning Division before the submittal package is final.

Monrovia cost ranges and L Square model pricing

Monrovia's Community Development Department publishes the ADU Ordinance and the Pre-Approved ADU Plan Program on the city's ADU page. Building and Safety permit review fees are collected separately and depend on the project valuation. L Square model prices for ADUs that meet the 1,200 square foot state ceiling start at $180,000 for the smallest prefab layout, with $240,000, $295,000, and $354,000 covering the larger 2 bedroom plans published on lscontractor.com/adu-cost-orange-county/. Those prices are the same for Los Angeles County cities including Monrovia, and they cover design, engineering, permits, and build for the published plan footprint. Site specific costs such as slope work, utility trenching, retaining walls, and code upgrades are quoted after the lot review. Confirm the current fee schedule with the Monrovia Planning Division. L Square holds California Contractors State License Board number 1095476 and writes every proposal in writing before any work starts.

Official Monrovia ADU sources

• The City of Monrovia Community Development Department Accessory Dwelling Units page lists the Pre-Approved ADU Plan Program, a Plan Submission Guide for Designers and Architects, an ADU FAQs page, and an ADU Forms and Resources page. The page states that the City is developing a catalog of pre-approved ADU plans for the public to choose from, and that the plans will be available to the public but residents must work with the design professional who prepared the plan for a fee. Official source
• The City of Monrovia Accessory Dwelling Units page states that the City updated its ADU Ordinance in February of 2025 to align with state housing legislation that took effect on January 1, 2025. The page notes that Junior ADUs are smaller living units ranging in size from 150 to 500 square feet and are created through the conversion of living space within an existing single family home. Official source
• The City of Monrovia ADU FAQs page states that state law allows a maximum of three ADU types per lot, two ADUs and one JADU, regardless of the number of detached single family dwellings on the lot. The page also states that a Junior ADU has a limited size of 500 square feet and is contained entirely within an existing or proposed single family structure. Official source
• The City of Monrovia Pre-Approved ADU Plan Program page states the City initially selected five prototype plans that met the State's Streamlined Permit Standards and were under 800 square feet, and that the plans reflect the architectural character of the City. The page also states that the Pre-Approved ADU Plans may be used in conjunction with single-family, multi-family, or mixed-use development, and that the plans are only for new detached structures and cannot be used to convert an existing garage or pool house. Official source
• California Government Code Section 66317(a)(3) gives the city 60 days to approve or deny a complete ADU application when an existing single family home is on the lot, and Section 66317(a)(2)(A) requires a completeness decision within 15 business days. Official source
• California Government Code Section 66314(d)(5) caps a detached ADU on a lot with an existing or proposed primary dwelling at 1,200 square feet of floor area, and Section 66314(d)(7) lets the city clear existing structures and same location rebuilds from the 4 foot setback ceiling. Official source
• California Government Code Section 66311.5(c)(1) bars a local agency, special district, or water corporation from imposing any impact fee on an ADU with 750 square feet of interior livable space or less, and impact fees above that floor are charged proportionately in relation to the primary dwelling square footage. Official source
• California Government Code Section 66325(a) states the ADU approval article supersedes a conflicting local ordinance, and Section 66325(b) does not authorize stricter standards than state law, only less restrictive ones. Official source