Thinking about building an ADU in Hillcrest or Mission Hills but not sure how the 2025 rules affect your numbers? You’re not alone. With new state laws and a major City of San Diego update, the math on size, unit counts, parking, and timelines has shifted. In this guide, you’ll see exactly what changed, how to run quick FAR math on your lot, and where to check parcel-specific rules so you can decide with confidence. Let’s dive in.
What changed in 2025
Owner occupancy removed
Most ADUs permitted after January 1, 2025 no longer require the owner to live on-site, which can improve rental options. Junior ADUs follow different rules, so check permit details for JADUs. See the state summary of AB 976 for context on this change. (Holland & Knight)
Faster permits with pre-approved plans
California now requires cities to post pre-approved ADU plans and to act on detached ADUs using those plans within 30 days. Using a pre-approved plan can cut time and design costs. Learn more about the 30-day rule under AB 1332. (ABAG)
Separate sale may be possible
State law lets cities allow separate sale of an ADU as a condominium if local procedures are met. San Diego adopted local rules in 2025 to enable this option consistent with AB 1033. Separate utilities, condo mapping, and other steps apply. (CalMatters bill record) (City summary)
San Diego’s code update is in effect locally
San Diego’s 2025 ADU update sets the local details that shape your project: unit counts, size caps, bonus program limits, some fees, fire setbacks, and separate-sale procedures. Most changes took effect August 22, 2025 outside the Coastal Overlay. Hillcrest and Mission Hills are inland, but always confirm parcel status and local procedures in the City’s bulletin. (Information Bulletin 400)
Local rules that shape your design
Size and unit counts
- ADUs can be up to 1,200 sq ft citywide. JADUs are 150 to 500 sq ft where allowed.
- Single-family lots often allow one JADU, one converted ADU, and one attached or detached ADU, subject to zone limits.
- Multi-dwelling lots have different allowances. All projects must still meet base zone limits on height, setbacks, lot coverage, and FAR. (Information Bulletin 400)
Bonus program caps and small-ADU fees
San Diego revised the ADU Bonus Program to limit total units in some zones and add a community enhancement fee for certain affordable or bonus ADUs under 750 sq ft outside Transit Priority Areas. Verify eligibility and caps before you model returns. (City update page)
Parking and TPA status
Outside a Transit Priority Area, the city now requires one off-street space for each affordable or bonus ADU. Within TPAs, state and local rules often reduce parking. Check your parcel’s TPA status before you finalize a site plan. (City announcement) (ADU toolkit)
Fire hazard setbacks
Parcels in High or Very High Fire Hazard Severity Zones need at least a 4-foot side and rear setback for ADUs, and additional fire-safety standards may apply. The 2025 map update changed coverage for some urban areas, so check your parcel. (Fire hazard zones) (KPBS overview)
Coastal and historic overlays
Some ADU provisions do not apply inside the Coastal Overlay until certified by the Coastal Commission. Historic or planned-district overlays can add steps. Confirm your parcel’s overlays in the City resources. (Information Bulletin 400)
Do the Hillcrest math step by step
Step 1: Pull parcel data
Use the Zoning & Parcel Information Portal to find your zone, lot area, max FAR, lot coverage, height, and overlays. These numbers drive your ADU size and placement. (ZAPP portal)
Step 2: Choose ADU type
Decide between a detached ADU, an attached addition or conversion, or a JADU. JADUs have different rules, including owner requirements. If you want the option to sell an ADU separately, review San Diego’s AB 1033 procedures early. (City update page)
Step 3: Run quick FAR math
- Lot: 5,000 sq ft in Mission Hills or Hillcrest
- Existing home: 1,800 sq ft
- Target detached ADU: 1,200 sq ft
- Total floor area: 3,000 sq ft
- FAR: 3,000 ÷ 5,000 = 0.60 Now compare 0.60 to your zone’s max FAR. If your zone allows 0.50, you would need to reduce the ADU size or consider an attached conversion to stay within limits. Also check setbacks and height. (Information Bulletin 400)
Step 4: Plan parking and placement
If you are outside a TPA and using the bonus program or building affordable ADUs, plan for one off-street space per such ADU. In mapped fire hazard zones, leave at least 4 feet along side and rear yards for access. (City announcement) (Fire hazard zones)
Step 5: Shorten the timeline
Using a city pre-approved plan can trigger a 30-day decision window for a detached ADU under AB 1332. This can reduce holding time and design fees. (AB 1332 basics)
Step 6: Include program fees and caps
If you plan to use the bonus program, model the community enhancement fee for certain smaller units outside TPAs and confirm the new caps tied to lot size and zone. (City update page)
Two quick scenarios
Small-lot Hillcrest example
On a 5,000 sq ft lot with a 1,800 sq ft home, a 1,200 sq ft detached ADU produces a 0.60 FAR. If your zone caps FAR at 0.50, consider a smaller detached ADU or convert interior space to create an attached ADU or a JADU. Confirm setbacks and, if mapped in a fire hazard zone, maintain at least 4 feet at side and rear.
Larger-lot bonus interest
On a 12,000 sq ft lot, start by confirming the zone and whether bonus ADUs are allowed under the revised program. Next, run FAR and lot coverage for your target mix, add the required parking if you are outside a TPA, and include any community enhancement fees for smaller affordable or bonus units. This will show whether your concept pencils. (City update page)
How the changes affect returns
- No owner-occupancy for most new ADUs can make long-term rentals more flexible. (Holland & Knight)
- Pre-approved plans and a 30-day review window can compress your schedule. (ABAG)
- Separate sale, where allowed by San Diego’s ordinance, can provide an additional exit option if you complete the required condo steps. (City update page)
What to verify before you design
- Zone, FAR, lot coverage, height, and setbacks in ZAPP.
- TPA status, which affects parking and bonus rules. (ADU toolkit)
- Fire hazard status and access clearances on the 2025 map. (Fire hazard zones)
- Overlays such as Coastal or historic, and their processing timelines. (Information Bulletin 400)
Ready to run parcel-specific numbers or map out a build-to-rent or sell-separately strategy in Hillcrest or Mission Hills? Reach out to the local team that pairs boutique attention with high-level execution. Connect with Ryan & Tracie to evaluate feasibility, line up trusted vendors, and plan your next steps.
FAQs
Can I build a 1,200 sq ft ADU in Hillcrest?
- 1,200 sq ft is the city cap for ADUs, but your final size must meet your parcel’s zone limits on FAR, lot coverage, height, and setbacks. Confirm in ZAPP and the City bulletin. (Information Bulletin 400)
Do I have to live on the property if I add an ADU?
- For most ADUs permitted after January 1, 2025, no. AB 976 removed the owner-occupancy requirement. JADUs are treated differently, so confirm permit conditions. (Holland & Knight)
Can I sell an ADU separately from my house in San Diego?
- Possibly. San Diego adopted procedures to allow separate sale consistent with AB 1033. You must follow local condo mapping, utility separation, and subdivision rules. (City update page)
How fast can I get a permit with a pre-approved plan?
- If you use a locally pre-approved plan for a detached ADU, the City must approve or deny within 30 days. Other submissions generally follow the standard ministerial timeline. (AB 1332 basics)
What fire rules apply to ADUs near canyons or hillsides?
- In High or Very High Fire Hazard Severity Zones, plan for a minimum 4-foot side and rear setback and expect additional fire-safety standards as required by the Fire Department. Check parcel status on the 2025 map. (Fire hazard zones)
Is Hillcrest or Mission Hills inside the Coastal Overlay?
- These neighborhoods are generally inland and outside the Coastal Overlay, but verify parcel-by-parcel. Some ADU changes are not effective inside the Coastal Overlay until certified. (Information Bulletin 400)
