ADU insurance basics
Insuring your ADU in California
Building a backyard cottage or converting the garage is a big investment, and it's easy to assume your homeowners policy has it covered. Sometimes it does, sometimes only partly. Here's a friendly overview of how coverage usually works, so you can walk into a conversation with your agent knowing what to ask.
Last reviewed October 17, 2026
1 · You, your family, or no rent
When the ADU is for personal or family use
Attached ADUs and garage or in-home conversions are usually treated as part of the main house, so they generally fall under the dwelling coverage (Coverage A) of a standard homeowners policy (often an HO-3). The catch: your dwelling limit has to grow to account for the added square footage, so tell your insurer before construction finishes.
A detached ADU is often treated as an "other structure" (Coverage B). On many standard policies Coverage B defaults to about 10% of the dwelling limit, so a $600,000 dwelling limit might leave roughly $60,000 for every detached structure on the lot combined, including the ADU, a garage, and fences. That's a common default, not a rule: some insurers use different percentages or let you schedule the ADU separately or add it as its own dwelling.
Rebuild costs in California can easily exceed that. Contractor quotes for new ADU construction often land in the hundreds of dollars per square foot, and costs vary a lot by region, size, and finish level. Ask your agent for a replacement-cost estimate for your specific unit, and raise limits if needed.
Family members can be a gray area. Some policies cover relatives who live in the household, but a relative in a separate unit, especially one paying rent, may not count. Ask how your insurer treats your exact arrangement and whether they need to cover the relative's own belongings (usually they'll want their own renters policy).
Sources: CA Dept. of Insurance: Home/residential insurance · Insurance Information Institute: Sample HO-3 policy form (PDF)
2 · Renting long-term
When you rent the ADU to a tenant
Standard homeowners policies typically exclude or limit coverage for a structure that's rented to someone who isn't living in the main house. Many policy forms, including the common ISO HO-3, exclude other structures rented to someone other than a tenant of the dwelling. If you collect rent, assume you need to tell your insurer and change something.
Common fixes are a landlord or dwelling fire policy for the rental (DP-3 is a common open-perils form), or an endorsement added to your homeowners policy. Which one fits depends on the insurer and whether the ADU is attached or detached.
- Property coverage for the ADU building itself
- Landlord liability, in case a tenant or guest is hurt on your property
- Loss of rents (fair rental value), if a covered loss makes the unit unlivable
- Encourage your tenant to carry renters insurance; your policy usually won't cover their belongings
Sources: CA Dept. of Insurance: Home/residential insurance · Insurance Information Institute: Coverage for renting out your home · III sample HO-3 form, Coverage B (PDF)
3 · Airbnb, Vrbo and short stays
Short-term rentals
Short-term renting is often excluded or limited as "business" activity under homeowners and even some landlord policies. Insurers that allow it usually require a home-sharing endorsement or a policy designed for short-term rentals.
Platform programs (such as host protection offered by booking sites) are not the same as your own insurance, have their own limits and exclusions, and may not cover everything. Also check your city's rules: many California cities restrict or ban short-term rental of ADUs, and some ADUs approved under state law can't be rented for terms shorter than 30 days.
Sources: NAIC: Insurance implications of home-sharing (PDF) · Insurance Information Institute: Coverage for renting out your home · Cal. Gov. Code §66323 (ADU short-term rental limits)
4 · California-specific
Earthquake
Standard homeowners and landlord policies don't cover earthquake shaking damage. Earthquake coverage is a separate policy or endorsement, from the California Earthquake Authority (CEA, sold through participating insurers) or from private insurers.
Important for ADUs: a CEA homeowners policy covers the dwelling, and structures not attached to it (like a detached garage or, generally, a detached ADU) are excluded. If your ADU is detached, ask specifically how it would be covered, which may mean a private earthquake policy. Earthquake deductibles are usually a percentage of the coverage limit, not a flat dollar amount.
Sources: California Earthquake Authority: Homeowners coverages and deductibles · CEA sample homeowners policy (PDF)
4 · California-specific
Flood
Flood damage is also excluded from standard homeowners policies. Flood insurance is available through FEMA's National Flood Insurance Program (NFIP) and from private flood insurers, and you don't need to be in a mapped high-risk zone to buy it.
NFIP policies generally have a 30-day waiting period before they take effect (with a few exceptions, such as buying it when you close a loan), and single-family residential building coverage tops out at $250,000. Under the NFIP, detached garages get limited coverage under the main policy, but other detached buildings, which would generally include a detached ADU, need their own building policy. Ask your agent how your unit would be classified.
Sources: FEMA FloodSmart: Buy a flood insurance policy · FEMA: Waiting period for a flood policy
4 · California-specific
Unpermitted ADUs
If an ADU was built or converted without permits, tell your agent. Not disclosing it could cause problems at claim time, and some insurers may decline to cover it, limit coverage, or not pay to rebuild to current code. It can also complicate a home sale or refinance.
California has a path for many older unpermitted ADUs: local agencies generally can't deny a permit to legalize an ADU built before 2020 just because it violated building standards, unless correction is needed for health and safety. Legalizing the unit can make insuring it simpler.
Sources: CA Dept. of Insurance: Home/residential insurance · Cal. Health & Safety Code §17980.12 (unpermitted ADUs)
4 · California-specific
If you're on the California FAIR Plan
The FAIR Plan is California's insurer of last resort for people who can't find coverage in the regular market. Its dwelling policy is named-peril and fire-focused: fire, lightning, internal explosion, and smoke, with optional add-ons like wind and vandalism. It doesn't include liability or theft, and much water damage isn't covered.
That's why FAIR Plan homes are usually paired with a separate Difference in Conditions (DIC) policy, which the FAIR Plan doesn't sell. For an ADU, check how both policies treat it: the FAIR Plan's sample dwelling form limits other-structures coverage to 10% of the dwelling limit unless you schedule the structure, and it excludes other structures rented to someone who isn't a tenant of the main home. A rented ADU may need its own FAIR Plan rental policy plus landlord liability elsewhere.
Sources: California FAIR Plan: Dwelling policies · California FAIR Plan: Difference in Conditions · CDI: Insurers that sell DIC policies
Questions to ask your agent
Bring this list to your next call. A good agent or broker will be glad you asked.
- Is my ADU covered as part of the dwelling, as an other structure, or does it need its own policy?
- What would it cost to rebuild my ADU today, and are my limits high enough?
- Do I have replacement cost or actual cash value, and is there extended replacement cost?
- Does renting it (long-term, to family, or short-term) change my coverage? What do I need to add?
- Do I have liability and loss-of-rent coverage for the ADU?
- How would earthquake and flood coverage apply to a detached ADU? What are the deductibles?
- Does it matter that part of the unit was built without permits?
- If I'm on the FAIR Plan, how do my FAIR Plan and DIC policies each treat the ADU?
- Do I need to update my coverage during construction (builder's risk or course of construction)?
Quick answers
Does homeowners insurance cover an ADU in California?
Often partly. Attached ADUs usually fall under dwelling coverage; detached ADUs often fall under Other Structures, which on many policies defaults to about 10% of the dwelling limit. Renting the ADU usually changes things. Check your policy and talk to a licensed agent.
Do I need landlord insurance if I rent my ADU?
Usually you need either a landlord/dwelling fire policy (such as a DP-3) or an endorsement, because many homeowners policies exclude structures rented to someone outside the household.
Does the CEA cover a detached ADU?
Generally not under a CEA homeowners policy, which excludes structures not attached to the dwelling. Ask an agent about private earthquake options.
How do I check an insurance agent's license?
Use the California Department of Insurance license lookup at cdicloud.insurance.ca.gov.