A Junior Accessory Dwelling Unit (JADU) is a compact living space—up to 500 sq ft—created within or attached to an existing single-family home. Designed for long-term residential use, a JADU must include a separate exterior entrance, a kitchenette and either its own bathroom or direct access to one in the main residence. Utility connections are typically shared with the primary dwelling.
JADUs emerged in California under state laws (2017–2020) aimed at increasing housing supply and affordability. Legislation allows homeowners one JADU plus one full-size ADU per lot, reducing zoning barriers and streamlining permits.
While both JADUs and ADUs add living space, ADUs can be up to 1,200 sq ft (varies by jurisdiction), include full kitchens and baths, and may be detached. JADUs are always within or attached to the main home and have limited kitchen facilities.
DADUs (Detached ADUs) are standalone structures. “Granny flats” and “casitas” often refer colloquially to ADUs or DADUs but lack formal size and attachment criteria—unlike state-defined JADUs.
Accurate terms ensure compliance with zoning, building codes and permit applications. Mislabeling a JADU as an ADU (or vice versa) can trigger revisions, fines or denial of approval.
State law limits JADUs to 500 sq ft, mandates kitchenette installation, requires owner occupancy and prohibits short-term rentals under 30 days.
City or county ordinances may impose setbacks, height limits or design guidelines. Many jurisdictions waive additional parking requirements for JADUs to promote infill housing.
Homeowners must reside in either the main house or the JADU. Tenancies must be at least 30 days; vacation-rental use is typically prohibited.
Permitting involves submitting site plans, floor plans and structural details. Impact fees for JADUs are often reduced or waived. Approval timelines range from 60 to 120 days, depending on local review capacity.
Rental income is taxable; depreciation may be claimed. Insurance premiums can rise; homeowners must notify carriers of added dwelling units to ensure proper coverage.
Converting an existing bedroom or garage into a JADU typically costs $30,000–$80,000, depending on finishes and structural modifications.
Permit and impact fees for JADUs can range from $1,500 to $10,000, though many cities offer reduced rates to encourage construction.
At $1,200 monthly rent, a $50,000 investment yields roughly 3.5% annual return; payback in 5–7 years, excluding tax benefits and appreciation.
Conversions minimize excavation and roof work but may require structural reinforcements; new builds allow customized layouts but cost more.
Choose professionals experienced in small-footprint residential conversions and local building codes. Get three bids and check references.
500 sq ft is the statewide cap under California law.
A separate exterior entrance is mandatory; a private bathroom is ideal, but shared access to the home’s bathroom is allowed if code compliant.
Yes, long-term tenants (30+ days) are permitted; short-term rentals are generally prohibited.
Permit fees and impact fees for JADUs are often lower or waived to incentivize small-scale in-law units.
Yes, homeowners must live in either the main house or the JADU for the duration of ownership.
Many jurisdictions waive additional parking for JADUs; some may require one off-street space or none, depending on transit proximity.
Search your city/county website for “planning department” or “building division.” Contact via phone or online portal for JADU guidelines.
Most agencies offer downloadable permit applications, design checklists and fee calculators on their websites.
Consult the California Department of Housing & Community Development’s ADU guide and your municipality’s zoning code for detailed standards.
Adding a JADU can be an efficient way to increase rental income, boost property value and enable multigenerational living. By understanding size limits, legislative requirements and cost factors, homeowners can plan a compliant project that balances benefits, expenses and timeline. Start by researching local regulations, sketching preliminary layouts and reaching out to your planning department—your JADU ribbon-cutting ceremony is within reach.
