Accessory dwellings, read from the parcel first.
You want room for someone else: family, a tenant, or your own work.
- Range
- $250K–$550K
- Construction
- 3–9 months
- Warranty
- Two years, workmanship
A guest house, a studio, an income unit, a parent close but not inside. California now allows them on lots where it did not a decade ago.
What California now allows, on a lot like yours.
Choose a unit, size it, place it in the garden. The rules alongside are state law: the floor every city and the County must meet.
- On a single-family lot the state allows a converted unit, a junior unit and a new detached unit, all three at once.
- A new detached unit of up to 800 ft², 4 ft from the side and rear lines and 16 ft high, must be allowed.
- No impact fees on a unit of 750 ft² or less.
- 15 business days to flag an incomplete application; 60 days to decide a complete one.
- In the Coastal Zone a coastal permit still applies.
$380K – $550K · 7 – 9 months
California law as of September 2026: HCD Accessory Dwelling Unit Handbook, March 2026 (PDF) (opens in a new tab); 2026 changes (SB 543, AB 1154) (PDF) (opens in a new tab). Sizes are interior livable space. Local ordinances can allow more; we confirm yours.
The square feet are not the cost.
Three things move the budget more than area. All are knowable before design begins.
Utilities
Sewer lateral capacity, the electrical upgrade the main house may now need, and the trench between them. Eighty feet out with the panel at capacity, those three can reach a sixth of the project.
Access
Whether a concrete truck and a lumber delivery can reach the site changes the labor cost of every phase after. Narrow side yards and shared driveways are common here. We price them.
Jurisdiction
Santa Barbara, Goleta, Carpinteria and the unincorporated County each run a different review; the coastal zone adds another. That path sets your schedule far more than the drawings.
Typical ranges
| Type | Build cost | Size | Construction |
|---|---|---|---|
| Detached new build | $380K – $550K | 600 – 1,200 ft² | 7 – 9 months |
| Garage conversion | $250K – $360K | 400 – 700 ft² | 5 – 7 months |
| Junior unit within the house | $250K – $310K | to 500 ft² | 3 – 6 months |
| Attached addition | $320K – $480K | 500 – 900 ft² | 6 – 8 months |
If income is the point.
Short-term rental rules differ by jurisdiction; state law lets a city or county require terms over 30 days. Check before counting on nightly rates. Property tax on the unit: ask the county assessor.
Accessory dwellings we have built.
Palo Alto
Ground-up accessory dwelling, with pool
A ground-up accessory dwelling in Palo Alto, with a pool and an outdoor kitchen.
See the project
Carpinteria
Junior unit, converted from the garage
A junior accessory dwelling unit converted from a garage in Carpinteria: a vaulted kitchen with butcher-block counters, a tiled bath, and a door to the garden.
See the projectBuilt by Matt Newman. Licensed since 2001. Salt Lake City, Los Angeles, twenty years on this coast, and on every AMN site himself. One name on the contract. His story
Send us the address. We'll tell you the truth about it.
Email it to purchasing@amnbuild.com. Matt reads it himself and writes back within two business days.
- Same dayMatt confirms he has it, and flags anything obvious that is missing.
- Within two business daysA written reading of your parcel: jurisdiction, review bodies, an order of cost and the permit path.
- Then nothing, unless you askNo follow-up sequence, no call from anyone else. The reading is yours to keep.
CSLB 802739 · Class B General Building · Licensed and insured · Two-year workmanship warranty, in writing
Updated November 2026