Garden Grove’s ADU rules are in Municipal Code Chapter 9.54. On a single-family lot, you can generally build a detached ADU up to 850 square feet for a studio or 1-bed and up to 1,200 square feet for 2+ bedrooms, at 16 feet tall with 4-foot side and rear setbacks. JADUs can be up to 500 square feet. In March 2026, the state housing department (HCD) found parts of the ordinance out of compliance with state law, so a few local rules are weaker than they look on paper.
Garden Grove is one of the best ADU cities in Orange County for buyers who want a bigger lot at a lower price. I wrote about why in The Complete ADU Guide to Garden Grove. This post is the rulebook: what the code says, what HCD flagged and what it means for a lot you’re thinking about buying.
Garden Grove ADU Rules at a Glance
| Standard | Garden Grove (Ch. 9.54) |
|---|---|
| Detached ADU size | 850 sq ft (studio/1-bed), 1,200 sq ft (2+ bed) |
| Attached ADU size | 850 sq ft or 50% of the home (studio/1-bed); 1,200 sq ft or 50% (2+ bed), whichever is less. Up to 800 sq ft if the home is under 1,600 sq ft. |
| JADU size | 500 sq ft, inside the existing home |
| Detached height | 16 ft; 18 ft within 1/2 mile of major transit (+2 ft for roof pitch) |
| Attached height | Up to 25 ft or the main home’s limit, 2 stories max |
| Side and rear setbacks | 4 ft; none for conversions of existing space |
| Parking | 1 space per new ADU, with state exemptions (transit, conversions and more) |
| Rentals | 30 days minimum. No short-term rentals. |
| Owner occupancy | Not required for ADUs. Required for JADUs. |
| Impact fees | None under 750 sq ft |
| Approval | Ministerial, within 60 days of a complete application (30 days for pre-approved plans) |
Source: Garden Grove Municipal Code Chapter 9.54. Always confirm with the city’s planning counter before you buy.
How Many ADUs Can You Build in Garden Grove?
- Single-family lot: the city code allows one ADU and one JADU. State law (Government Code 66323) also lets you combine a detached ADU, a conversion ADU and a JADU on many lots, and state law controls where the two conflict. Ask the city which combination it will approve on your lot.
- Existing multifamily lot: up to 8 detached ADUs, but no more than the number of existing units. Plus conversions of non-living space up to 25% of the units (at least one).
- New multifamily lot: up to 2 detached ADUs.
For the bigger picture, see How Many ADUs Can You Add to a Multi-Unit Property.
What HCD Found Wrong With Garden Grove’s Ordinance
Garden Grove adopted Ordinance No. 2966 in August 2025. On March 30, 2026, HCD sent the city a findings letter saying parts of it don’t comply with state ADU law. The city had until April 29, 2026 to respond by amending the ordinance or explaining why it disagrees. The items that matter most to buyers:
- Minimum sizes. The code sets bedroom-based minimums (for example 500 sq ft for a 1-bed). HCD says those can’t apply to state-protected ADUs.
- Front setbacks. They can’t stop an 800 sq ft ADU with 4-foot side and rear setbacks.
- Garage setbacks and parking. HCD wants the state parking exemptions added and parking allowed in setbacks.
- 6-foot building separation. HCD says it can only apply to certain ADUs, not the state-protected 800 sq ft unit.
- Design review language. Approval has to stay objective, not “compatibility” judgment calls.
- Equipment screening and the 3-foot path rule. HCD says to remove them.
- JADU parking. HCD says JADUs can’t require any parking.
- Utility connections. Certain ADUs can’t be forced into a new connection or capacity charge.
Check with the city whether it has amended the ordinance since. Either way, state law is the floor. My California ADU Laws 2026 guide covers every state rule a city has to follow.
Setbacks, Height and the 800 Square Foot ADU
The rule that matters most when you’re shopping is the state-protected 800 square foot ADU. On almost any single-family lot in Garden Grove, the city has to allow an 800 sq ft detached ADU, 16 feet tall, with 4-foot side and rear setbacks, regardless of lot coverage or floor area limits. That’s why lot depth and the location of the existing garage matter more than total lot size. More on that in ADU Setback Requirements in Orange County.
Garden Grove ADU Fees
- Impact fees: none for an ADU under 750 square feet. Larger ADUs pay fees proportional to the size of the main home.
- Still charged: plan check, building permit fees and water and sewer charges where they apply.
- Separate utilities: optional. An ADU can share the main home’s connections, subject to the provider.
That 750 square foot line is changing. SB 1117, signed September 29, 2026, lets cities charge impact fees only on the square footage above 750 for the first two ADUs on a property. I break down the timing in SB 1117: The 750 Square Foot Fee Cliff Is Gone. That makes going bigger more of a rent question than a fee question. My Garden Grove ADU rent guide shows what each size rents for.
What the Rules Mean for Buyers
When I tour Garden Grove homes with a client, these are the rule-driven things I check first:
- Lot depth behind the house. Can an 800 to 1,200 sq ft unit fit with 4-foot setbacks?
- Detached garage. Converting it avoids most setback problems, and a typical garage is well under the 750 square foot fee line.
- Transit. Within a half mile of a major transit stop, parking may not be required and height goes to 18 feet.
- Sewer and water. Where the lines run, and whether a separate meter is realistic.
For full buy-and-build math, see Garden Grove Buy-and-Build ADU Numbers. If you’re considering a lot split instead, the Garden Grove SB 9 checklist covers that path. For current listings, see the October 2026 Garden Grove ADU market report.
Frequently Asked Questions
How big can an ADU be in Garden Grove?
Detached: 850 sq ft for a studio or 1-bed, 1,200 sq ft for 2+ bedrooms. JADUs: 500 sq ft. Conversions have no size cap if you don’t add floor area.
Does Garden Grove require parking for an ADU?
One space per new ADU, unless a state exemption applies. Common exemptions include being within a half mile of transit and converting existing space.
Do I have to live on the property to build an ADU in Garden Grove?
No, not for an ADU. A JADU does require the owner to live in the main home or the JADU.
Can I rent my Garden Grove ADU on Airbnb?
No. Garden Grove prohibits ADU and JADU rentals under 30 days.
Find a Garden Grove Lot That Fits the Rules
The rules decide what you can build. The lot decides whether it pencils. I’ll help you find a Garden Grove home where the ADU you want actually fits.
👉 Book a buyer ADU consult call to go through your options with Dylan
Prefer to talk now? Call Dylan Serna, ADU Realtor at 714-860-2868.
Dylan Serna | The ADU Realtor | eXp Realty | DRE #02217359
This post is general information, not legal advice. Confirm the rules for any specific property with the City of Garden Grove.
