ADU vs Room Addition — Which Is Right for Your LA Home (2026)
The single most common question LA homeowners ask: do I add a room, or build an ADU? The answer comes down to three factors — rental income, privacy, and permit path.
| Attribute | ADU (Accessory Dwelling Unit) | Room Addition |
|---|---|---|
| Typical LA cost | $200K–$450K+ | $80K–$300K |
| Typical timeline (permit → complete) | 6–12 months | 4–9 months |
| Permit path | Ministerial (SB 543/AB 130) — streamlined | Standard discretionary + LADBS plan-check |
| Rental income potential | $2,000–$3,500/month typical | None (counts as primary SFR space) |
| Resale value lift (LA 2026) | 20–30% more than cost | Typically 60–80% of cost recouped |
| Independence from main house | Separate entrance, kitchen, bath | Shared with main house |
| Setback/zoning flexibility | Relaxed per state law | Full R1 setbacks apply |
| Impact fees | $0 (SB 543 eliminates) | Full impact fees apply |
Takeaway
If you want rental income or multi-generational living: ADU. If you want more space for your family and need the footprint directly connected to the main house: room addition. Baily's chat walks you through the tradeoffs in 5 minutes.
Talk it through with Baily
Not sure which side fits your project? Ask Baily — we'll walk through the tradeoffs for your specific situation.
ADU vs Room Addition
Who is Baily?
Baily is named after Francis Baily — an English stockbroker who retired at 51, became an astronomer, and in 1836 described something on the edge of a solar eclipse that nobody had properly articulated before: a string of bright beads of sunlight breaking through the valleys along the moon's rim.
He wasn't the first to see them. Edmond Halley saw them in 1715 and barely noticed. Baily's contribution was clarity — describing exactly what was happening, in plain language, so vividly that the whole field of astronomy paid attention. The phenomenon is still called Baily's beads.
That's what we wanted our AI to do. Every inbound call and text has signal in it — a homeowner's real question, a timeline, a budget, a hesitation that means “yes but.” Baily listens to every one, 24/7, and finds the beads of light.
Baily was a businessman before he was a scientist. That's our vibe too.