ADU guides, page 5
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.
Rules
HCD ADU handbook: what California's 2026 guide says
What the state's March 2026 ADU handbook covers, what's new, how much weight it carries with your city and where to get it.
Updated Oct 26, 2026
Rules
Unpermitted ADU in California: how to legalize it under AB 2533
Who qualifies, what a city can still require, the fees it can't charge, San Diego's IB-242 process and what to disclose when you sell.
Updated Oct 26, 2026Building code
ADU building code: what California requires in 2026
Which code applies, fire separation between units, when sprinklers are required, ceilings, escape windows and solar.
Updated Oct 26, 2026
Rules
Building an ADU in a fire hazard zone in California
Whether a city can say no, the WUI code that replaced Chapter 7A, defensible space, sprinklers and San Diego's 4-foot rule.
Updated Oct 26, 2026Rules
SB 9 vs ADU: lot splits, duplexes and how they combine
What SB 9 allows next to ADU law, the lot split rules, whether you can stack SB 9 units and ADUs, and San Diego's version.
Updated Oct 26, 2026
Rules
What states allow ADUs? Statewide ADU laws compared
The 16 states whose laws make cities allow ADUs, what each requires, and how owner-occupancy, parking and size rules differ.
Updated Oct 26, 2026
Decisions
ADU pros and cons: is an ADU worth it in California?
The trade-offs of building an ADU: rent and family housing against cost, permits, fees and landlord duties, with San Diego numbers.
Updated Oct 26, 2026
Decisions
ADU vs addition: which adds space better in California?
Permits, setbacks, fees, property tax, cost and renting compared for an ADU and a room addition.
Updated Oct 26, 2026Financing
ADU loan calculator: monthly payments by amount, rate and term
Payment tables for $100,000 to $500,000 ADU loans, HELOC draw costs, interest during the build and how much to borrow.
Updated Oct 26, 2026
Hiring
ADU companies in California: how to compare builders
Design-build, prefab and general contractors compared: licenses, bids, deposits, payment schedules and what happens when a firm fails.
Updated Oct 26, 2026Value
Does an ADU increase property value?
How appraisers and lenders put a number on an ADU, why it often returns less than it costs, and what raises or lowers its value.
Updated Oct 26, 2026Property tax
ADU property tax in California: what gets reassessed
Only the new unit is assessed under Prop 13. How the assessor values an ADU, supplemental bills, exclusions and San Diego tax rates.
Updated Oct 26, 2026