ADU guides, page 4
68 guides on what an ADU costs, what the law allows and how to hire well. Every number links to the state law, city page or study it came from.
Design
ADU architects and designers: who can draw your plans and what it costs
Whether you need an architect, who else can legally design an ADU, what each costs and when pre-approved plans make more sense.
Updated Oct 26, 2026
Hiring
Design-build ADU vs hiring an architect: which route fits
How a design-build ADU and the architect route work, how contracts and payments differ, red flags and which one fits your project.
Updated Oct 26, 2026
Utilities
ADU utilities: meters, sewer, panels and what they cost
What a utility can require, whether you need a separate meter, sewer and panel upgrades, gas vs all-electric and a San Diego budget.
Updated Oct 26, 2026
Energy
ADU solar requirement and Title 24: does an ADU need solar?
Which ADUs need solar panels, the exceptions, system size, community solar and the other energy code rules that apply.
Updated Oct 26, 2026Conversions
Basement ADU and attic ADU: converting space inside your house
Conversion ADU vs JADU, no setbacks or size cap, the 150 sq ft access rule, and the code issues: ceiling height, egress, stairs, fire floors.
Updated Oct 26, 2026
Rules
ADU setbacks in California: the 4-foot rule and San Diego's limits
The 4-foot side and rear cap, front setbacks, zero setbacks for conversions and how San Diego cities apply them.
Updated Oct 26, 2026Rules
ADU height limit in California: 16, 18 and 25 feet explained
The state's minimum heights for detached and attached ADUs, the transit bonus, how height is measured and San Diego's limits.
Updated Oct 26, 2026
Rules
ADU parking requirements in California
The one-space maximum, when no parking is needed, what happens to a converted garage and how San Diego applies it.
Updated Oct 26, 2026
Permits
ADU coastal development permit: building an ADU in the coastal zone
When a coastal ADU needs a CDP, the 60-day clock, appealable areas and how San Diego's coastal cities handle it.
Updated Oct 26, 2026Rules
California ADU laws 2027: AB 956 and SB 1117
Two detached ADUs on single-family lots and impact fees only above 750 sq ft, both from January 1, 2027.
Updated Oct 26, 2026Multifamily
Multifamily ADU rules in California: how many units you can add
Conversions of up to 25% of units, up to eight detached ADUs, what SB 1211 changed, duplexes, parking and San Diego's rules.
Updated Oct 26, 2026
HOA
ADU HOA rules in California: what your HOA can and can't do
Why an HOA can't ban an ADU on a single-family lot, what counts as a reasonable restriction, the 2025 fee rule, rentals and the 2027 change.
Updated Oct 26, 2026