Local permit rules, fees, and timelines for San Dimas, verified against city sources, plus the loan options NestMade matches to your equity and the rent your unit can earn.
San Gabriel Valley ADU Loans
An accessory dwelling unit adds rental income, room for family, and value to your San Dimas property. The local details below — each checked against its city source — shape what you can build under California's ADU law and what it costs, alongside loan options matched to your equity and timeline.
The Numbers
San Dimas home values support the equity an ADU loan draws on, and local rents shape whether the unit pays for itself.
The median value of owner-occupied homes in San Dimas is about $801,800, so most owners hold meaningful equity to borrow against.
HUD's revised FY2026 Fair Market Rent for the Los Angeles County metro, which covers San Dimas, is $2,079 for a studio, $2,328 for a one-bedroom, and $2,903for a two-bedroom. Fair Market Rent is HUD's 40th-percentile gross rent, so a newly built ADU often asks somewhat higher.
What You Can Build
What the city allows on a single-family lot, checked against the local ordinance and state law.
San Dimas caps an ADU at 1,000 sq ft per its official ADU Brochure; if the ADU would push lot coverage over 35% it may be limited to less, but in no case can the lot-coverage limit prevent an ADU of at least 800 sq ft. An attached or conversion ADU may not exceed 50% of the existing residence or 1,000 sq ft, whichever is less, again with the 800 sq ft floor. A JADU must be within an existing/proposed single-family residence and no larger than 500 sq ft. The city's 2020 ordinance was found noncompliant by HCD, so it processes ADUs under State ADU Law.
San Dimas requires an ADU's architectural features to match the main residence's style (ADU Brochure 'Architecture'; ADU Requirements Sec. 2(b)). The city also restricts exterior doors on any elevation closer than 15 ft to a property line, though that may not preclude an ADU of 800 sq ft or less. Western/rustic theme controls apply only to the Historic Downtown commercial area, not residential ADUs; match-the-primary-dwelling is the operative standard.
San Dimas requires a 20-ft front setback for an ADU, but the front setback may not preclude an ADU of 800 sq ft or less. Side and rear setbacks (including street-side) are 4 ft, with a 6-ft building separation; maximum height is 25 ft (or the zone limit) and maximum lot coverage is 35% (which also may not prevent an 800 sq ft ADU). The city's ADU materials impose no separate ADU-specific front-yard landscaping standard.
San Dimas's ADU Brochure states a residentially zoned property with a single-family home can build one ADU and one JADU. The city's local ADU ordinance (Ord. 1281) was found noncompliant by HCD, which in 2025 recommended repeal; the city processes ADU applications under State ADU Law. Under state law a single-family lot supports at minimum one ADU plus one JADU ministerially, with a combinable converted ADU + detached ADU + JADU pathway.
Costs
What the city and school district charge, and where ADUs get a break.
Per the City of San Dimas Schedule of Fees & Charges (Resolution 2024-60), building permit fees for new residential construction (including ADUs) are valuation-based, computed on appraised value per square foot, plus plan-check, issuance, and separate mechanical/plumbing/electrical permit fees, with annual CPI escalation. There is no flat ADU fee; exact dollars depend on the assigned construction valuation and are confirmed at submittal.
San Dimas's ADU Brochure states impact fees may apply to any ADU over 750 sq ft, consistent with state law (ADUs under 750 sq ft exempt; larger proportional). City impact fees include a Parks & Recreation Open Space Development Fee of $400 (1-BR), $500 (2-BR), and $600 (3-BR). The school district is Bonita Unified School District, whose Level I residential developer fee is $4.79/sq ft (2022 study; confirm the current adopted rate). Under state law an ADU under 500 sq ft is not assessable for school fees.
Process
How long it takes, and the shortcuts the city offers.
No published pre-approved/standard ADU plan set was found for San Dimas. The city's Planning Division Informational Brochures page lists only an ADU flyer and the ADU Brochure under Accessory Dwelling Units, with no AB 1332 pre-approved-plan program or listing. AB 1332 still requires the city to pre-approve applicant-submitted plans on request; confirm any counter availability with Building & Safety.
San Dimas processes ADUs ministerially with no separate Planning application: complete plans and a building permit application are submitted to the Building & Safety Department, and for detached ADUs a soils report (footprint plus 5 ft) may be required. The ADU Requirements handout adds a 100A minimum electrical panel, full construction plans, LA County Fire Department fire-flow/hydrant approval prior to permit issuance, and a new address (existing + 'A'). Per state law the city determines completeness within 15 days and approves or denies within 60 days.
Watch-outs
A few local specifics that can affect where and whether you build.
Yes. San Dimas received updated 2025 OSFM/CAL FIRE LRA Fire Hazard Severity Zone maps (Mar 24, 2025) designating Very High, High, and Moderate areas; the north foothill/San Dimas Canyon area adjacent to the Angeles National Forest falls within the mapped zones. Any ADU on a property in a Fire Hazard Severity Zone must comply with the California Wildland-Urban Interface Code (ignition-resistant construction, defensible space/vegetation plan, Zone 0) and obtain LA County Fire approval before permit issuance.
San Dimas's ADU Requirements handout (Sec. 7) assumes connection to the public sewer: the new ADU's sanitary drainage 'shall be connected to the building sewer of the main unit' as a separate, independent line that may not pass under any structure, with no septic/leach-field path offered — indicating ADU-eligible lots are generally sewered. Some older foothill/canyon north-end lots may rely on private septic, which would trigger a percolation test and LA County Environmental Health review; the city publishes no parcel-level septic map.
No. San Dimas has not adopted an AB 1033 (Gov. Code §66342) ordinance allowing ADUs to be sold separately as condominiums. The city's ADU materials address rental (30-day minimum) but contain no separate-conveyance/condominium pathway, and no San Dimas AB 1033 ordinance was found. AB 1033 is opt-in, so absent adoption an ADU may not be sold separately from the primary residence.
Know Your Numbers
Pick your project and size for a quick, itemized estimate, then see whether to pay cash or finance it. Permit fees vary by city — the San Dimas specifics are in the fees section above.
1 What do you want to build?
2 How big?
3 Your estimated cost in San Dimas
Does it pencil?
The rent could fully cover the loan payment — about $1,140/mo left over.
Financing $154,000 at 8.5% over 30 years (illustrative). Potential rent is the HUD Fair Market Rent for LA County — your actual rate and rent will vary.
4 How will you pay for it?
Ballpark ranges based on 2025–26 Los Angeles–area ADU costs, not a quote. Your actual cost depends on your lot, finishes, site conditions, and city. Exact San Dimas permit fees vary — see the fee details on this page. A NestMade advisor will give you real numbers for your project.
Information last verified June 2026 against official San Dimas and California state sources.
The permit rules, fees, timelines, and figures on this page are provided for general informational purposes only and are not legal, tax, financial, or lending advice. Local ordinances and fee schedules change frequently, and your property's specifics may differ. Confirm current requirements directly with the City of San Dimas and do your own research with the appropriate licensed professionals before making decisions about your ADU. Cost figures are estimates; loan options are subject to credit approval and are not a commitment to lend.
San Gabriel Valley
ADU rules and fees differ from one city to the next. Explore the guidance for a nearby city, or see them all.
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Tell us about your home and your project. We will come back with the loan options that fit.
