ADU questions, answered

What is an ADU?

An accessory dwelling unit is a second, self-contained home on a lot with an existing or proposed primary dwelling. It has its own kitchen, bathroom and entrance, which is what separates it from a spare room or an addition.

Can I build an ADU on my property?

Only your permitting agency can confirm that for your parcel. It is decided by zoning, lot size, setbacks, coverage, height, utility and septic capacity and fire access. California sets statewide minimums local rules cannot go below.

How much does an ADU cost?

It depends on type, size, site conditions and jurisdiction, and any single national figure will be wrong for your project by a wide margin. We publish the cost structure and sourced California permit-valuation evidence, and our calculator builds a range from line items you supply.

How long does an ADU take?

Construction is usually months; design and permitting frequently take as long again. In California the agency must decide a completed application within 60 days and it is deemed approved if it does not (Gov. Code § 66317).

Do I have to live on the property?

In California, no — Gov. Code § 66315 prohibits a local owner-occupancy requirement for an ADU on a single-family lot. Junior ADUs are treated separately, and outside California owner-occupancy requirements remain common.

Will I lose my parking if I convert the garage?

You lose the garage, but in California the agency cannot require you to replace the off-street parking it provided — Gov. Code § 66314(d)(11).

Can I rent my ADU?

Usually, long-term. A unit created under California’s by-right provisions must be let for terms longer than 30 days (Gov. Code § 66323), which rules out short-term letting under that route. Cities regulate short-term rentals separately.

How big can my ADU be?

California prohibits a local maximum below 850 sq ft, or 1,000 sq ft for more than one bedroom, and nothing may prevent an 800 sq ft unit with four-foot setbacks. Your city may allow more. Staying at or under 750 sq ft exempts the unit from impact fees.

Does an ADU increase my property tax?

In California the ADU is typically assessed as new construction without reassessing the whole property. The detail matters and varies; see our property tax research.

Does HyreADU build ADUs?

No. We publish research and pass homeowner inquiries to professionals. We do not design, permit, build, finance or let ADUs, and we do not supervise anyone who does.

Still deciding?

Work through the journey in order: what you could build, then whether your lot takes one, then what decides the cost, then what approvals it needs.

When you want options from professionals, tell us about your project.