SB 1211 for 20-unit apartment in Walnut Creek
Walnut Creek's SB 1211 math for 20-unit apartment owners: 8 detached ADUs (the §66323 cap), plus 5 interior conversions. Total: 13 new homes. At Walnut Creek's median rent of $2,700/mo, that's ~$421K in additional gross annual rent.
The Walnut Creek scenario
Run it as a sequence: stabilize existing 20 units → permit 8 detached ADUs ministerially under §66314 → convert 5 interior spaces into rentable units → re-tenant at Walnut Creek medians.
Local tip for Walnut Creek: Tree preservation ordinance can affect placement.
Large multifamily (10+ unit) design playbook
A 20-unit complex is capped at 8 detached ADUs by statute, so the play shifts toward interior conversions: max(1, ⌊units × 25%⌋) = 5 additional units carved from common rooms, oversized lobbies, basement storage, or laundry rooms.
Pro-forma snapshot
| Existing units | 20 |
| Detached ADUs (SB 1211) | 8 |
| Interior conversions | 5 |
| Total new units | 13 |
| Median 1BR rent in Walnut Creek | $2,700/mo |
| Est. additional gross rent | $421K/yr |
| Estimated total project cost | ~$2,621K |
| Year-1 NOI estimate | ~$316K |
| Stabilized cap rate at cost | 12.1% |
| Replacement parking required | No (§66313) |
| Approval pathway | Ministerial · §66314 |
| Typical permit timeline in Walnut Creek | 75-120 days |
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