Standards & rules
Interior conversion ADUs under SB 1211
The 25%-of-units rule and how it stacks with detached ADUs.
The interior-conversion provision lets owners carve up to max(1, ⌊units × 25%⌋) additional units out of existing common areas: lobbies, laundry rooms, basement storage, oversized hallways, manager units.
For a 12-unit building, that's 3 interior conversions. For a 32-unit building, 8. Combined with 8 detached ADUs, large complexes can add 16 new units total — a 50% density increase on the same lot.
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Related standards & rules topics
SB 1211 parking requirementsHow SB 1211 changes parking rules: cities can no longer require 1:1 replacement for parking removed to build ADUs.SB 1211 setback requirementsFour-foot side and rear setbacks. 18-foot height limit. The objective standards explained.SB 1211 height limits18 feet maximum for detached ADUs. How that affects two-story designs.Fire code compliance for SB 1211 ADUsThe one local power that survives ministerial review.Utility hookups for multifamily ADUsWater, sewer, gas, electric requirements under SB 1211.Impact fees on SB 1211 ADUsAB 1033 + SB 13 already capped fees on smaller ADUs. SB 1211 inherits those protections.Converting surface parking under SB 1211The biggest unlock. How to assess your parking lot for ADU potential.ADU design under SB 1211What objective standards mean for layout, placement, and unit mix.
How this topic plays in different cities
SB 1211 in Rancho CucamongaSan Bernardino County · $2,100/moSB 1211 in WestminsterOrange County · $2,400/moSB 1211 in EscondidoSan Diego County · $2,200/moSB 1211 in El MonteLos Angeles County · $2,200/moSB 1211 in Palo AltoSanta Clara County · $3,300/moSB 1211 in VallejoSolano County · $2,100/moSB 1211 in StocktonSan Joaquin County · $1,600/moSB 1211 in Thousand OaksVentura County · $2,700/moSB 1211 in RiversideRiverside County · $1,800/moSB 1211 in GlendaleLos Angeles County · $2,600/moSB 1211 in FresnoFresno County · $1,500/moSB 1211 in IrvineOrange County · $2,900/mo
By property type
Duplex2-unit · up to 3 new ADUsTriplex3-unit · up to 4 new ADUsFourplex / 4-unit4-unit · up to 5 new ADUs5-unit apartment5-unit · up to 6 new ADUs6-unit apartment6-unit · up to 7 new ADUs8-unit apartment8-unit · up to 10 new ADUs10-unit apartment10-unit · up to 10 new ADUs12-unit apartment12-unit · up to 11 new ADUs16-unit apartment16-unit · up to 12 new ADUs20-unit apartment20-unit · up to 13 new ADUs24-unit apartment24-unit · up to 14 new ADUs32-unit apartment32-unit · up to 16 new ADUs