On March 4, 2026, the San Diego County Board of Supervisors voted unanimously to amend the zoning ordinance. The headline everyone noticed: Assembly Bill (AB) 1033 condo-conversion authority, which lets owners sell ADUs as separate units. The number that actually rewrites permit sets: up to 8 detached ADUs on a lot with an existing multifamily dwelling, up from a cap of 2.
The amendment took effect April 4, 2026, and we've already seen the permit-pipeline shift. A 12-unit apartment owner in unincorporated Lakeside who maxed out at two backyard ADUs last year can now order six more. That's not a line-item addition—it's a scope re-draw that touches every trade, every service calc, and every fire-sprinkler coordination meeting.
Why the Jump From 2 to 8 Changes Everything
Before April, a "two-ADU add-on" meant a single set of stamped plans with modest utility upsizing and maybe one shared transformer pad. Now an eight-ADU project looks more like a mini-subdivision:
- Plan-sheet count quadruples. Each detached unit needs its own foundation, roof, and electrical service detail. MEP coordination sheets multiply.
- Utility-service calcs scale nonlinearly. Going from 12 units + 2 ADUs to 12 units + 8 ADUs triggers different load tables, different transformer sizing, and often a second gas-meter bank.
- Fire-sprinkler review gets complicated. San Diego County's building official may require a single hydraulic calc covering all structures, or separate calcs with a shared backflow assembly—either way, the fire-protection engineer's fee isn't linear.
- Subcontractor lineup changes. Concrete crews that pour two slabs on a Thursday now block three days for eight. Framing schedules shift. Plumbers juggle eight water-service tie-ins instead of two.
For multifamily developers and general contractors in the county's unincorporated zones, the old permit budget and the old schedule don't work anymore.
We're also seeing clients rethink phasing. An owner who planned two ADUs this year and two next year can now submit all eight at once, lock in today's fee schedule, and stagger construction. That bundles permit costs but spreads labor risk—smart if you've got subs on retainer, risky if you're hunting framers week-to-week.
AB 1033: When the ADU Becomes a For-Sale Product
The condo-conversion piece—AB 1033—matters even if the owner plans to hold and rent. Once an ADU can be sold separately, lenders start asking whether the permit-of-record supports independent legal description. That means:
- Tighter permit accuracy. A missed setback dimension or an un-stamped truss package that wouldn't tank a rental project can kill a for-sale appraisal.
- Title-policy scrutiny. Buyers' title insurers will order their own permit confirmations. Any "substantially complete per approved plans" language in the final inspection report gets parsed by attorneys, not just building officials.
- Appraisal coordination. The appraiser needs to see eight independently marketable units, not "one lot with improvements." That flows back to how the site plan, utility services, and legal descriptions are drawn.
Even clients who tell us "we're keeping these as rentals" are asking for AB 1033–ready permit sets, because exit optionality has value. If cap rates compress or a 1031 buyer surfaces, the ability to sell individual ADUs instead of the whole parcel changes the math.
For more detail on how AB 1033 condo conversions work across California jurisdictions, see our ADUs & Casitas service page.
What the New Cap Doesn't Cover
Two limits in the amendment still catch people:
1. Proposed multifamily projects are still capped at 2 detached ADUs. The eight-unit allowance applies only to lots with an existing multifamily dwelling. If you're breaking ground on a new 16-unit building, you can't add eight detached ADUs on day one—you're stuck at two until the building gets a certificate of occupancy and becomes "existing."
2. Incorporated cities write their own rules. This is a county ordinance for unincorporated San Diego County. Chula Vista, Carlsbad, Oceanside—they each have separate ADU codes. Some may follow the county's lead; others won't.
We've had clients assume the eight-ADU rule applies countywide and then discover their El Cajon parcel is inside city limits. Always confirm jurisdiction before you pay for civil engineering.
Permit-Pipeline Implications
Since April 4, we've seen three patterns:
- Scope creep at intake. Owners who submitted two-ADU plans in March are calling back in May to add six more. That triggers a full re-review because the original utility calcs and fire-access layouts don't cover eight units. Faster to pull the first submittal and resubmit as an eight-pack.
- Expedited-review requests spiking. Eight ADUs means eight sets of fees, but it also means eight times the plan-check comments if anything's wrong. Clients are paying for permit expediting to get all review cycles done in parallel instead of serial.
- MEP coordination moving earlier. On a two-ADU job, the electrician and plumber could finalize service routing during rough-in. On an eight-ADU job, the county wants to see a full MEP coordination set up front—especially if you're sharing a single fire-sprinkler backflow or upsizing the gas main.
The county's plan-review queue hasn't magically grown to handle 4× the ADU volume, so turnaround times are stretching. Budget an extra two weeks for first review if you're submitting after June.
Who This Rule Actually Helps
The eight-ADU cap isn't useful for every multifamily owner. It works best when:
- You've got deep lots (at least 10,000 sq ft per ADU to stay clear of setbacks and fire-access lanes).
- Your existing building is low-density—think a 6-unit 1970s walk-up with half the lot still grass. Tight urban infill parcels hit coverage limits before they hit the ADU count cap.
- You can phase construction over 18–24 months. Pouring eight slabs in one go is a cash-flow hammer; pouring two every six months spreads the pain.
- You're in an unincorporated pocket where the county is the AHJ. This doesn't apply inside city limits.
If all four conditions line up, the April 4 amendment is a genuine revenue opportunity. If not, you're still capped at two detached ADUs—or you're looking at attached ADUs under a different section of the ordinance.
For help sorting out which ADU strategy fits your San Diego County parcel, reach out—we draft permit sets for unincorporated-county projects across all California jurisdictions.
What to Watch Next
The county hasn't published updated plan-check guidelines yet. The March 4 ordinance is law, but the building division's internal checklists—setback tables, utility-service matrices, fire-access templates—are still catching up. We're seeing inconsistent interpretations between plan reviewers, especially on:
- Whether all eight ADUs can share a single water service or need individual meters.
- How to calculate lot coverage when the existing multifamily building plus eight ADUs approach 60%.
- Fire-department access-lane width when ADUs are clustered in a rear-yard "courtyard" layout.
Those details will settle over the next 90 days as more eight-ADU sets move through review. In the meantime, expect correction cycles and be ready to justify your layout with code citations.
The condo-conversion piece—AB 1033—is already generating its own set of title and appraisal questions. We'll cover those in a separate post once we've seen a few AB 1033 sales close and can report real numbers.
For now, if you own existing multifamily in unincorporated San Diego County and you've been sitting on ADU plans, April 4 changed your ceiling. The question is whether your lot, your budget, and your construction capacity can actually use all eight slots—or whether the smarter play is still two or four units with faster permitting and simpler coordination.