ADUs in Altadena
An ADU for your Altadena lot, priced before you sign.
We design, permit and build standard ADU models in Altadena and across LA County. If you lost your home in the Eaton fire, the ADU can be finished first, and your family can live in it while the house is rebuilt.
★ 4.9 on Google · 25+ reviewsCSLB License #1134744Four models from 325 to 996 sq ft
The models
Four standard homes, each with a price up front.
Starting prices include design, permitting and construction with standard finishes. Site work and utilities generally run $15,000 to $35,000 and are priced after we see your lot, and County permit fees are billed at cost. See what's included.
After the Eaton fire
Live in your ADU while the house is rebuilt.
On a lot where the house was destroyed or substantially damaged in the Eaton fire, the ADU can be finished and occupied before the new house. In unincorporated LA County, which includes Altadena, your household can live in it until January 7, 2030 while you rebuild. When the house goes up, the ADU stays, with no further review.
Executive Order N-9-25, in effect until January 16, 2028 unless ended earlier; LA County Planning Interpretation No. 2025-04.
County permit fees, deferred
If you owned and lived in your home on or before January 7, 2025, LA County defers its plan review, permit and inspection fees for your rebuild, including an ADU, and doesn't collect them later. It covers your primary residence only. Rentals and LLC-owned lots don't qualify, and school district and utility fees aren't included.
Around Altadena
Buildoly projects in Altadena and east Pasadena.
Each pin is a Buildoly project near Altadena: 3 design-and-build and 3 design-only. See the full map.
Altadena ADU rules in plain English
What you can build in unincorporated LA County.
Altadena is unincorporated, so LA County's ADU rules apply. These are the basics for a single-family lot. Every lot is different, so we confirm each of these for your address before we price anything.
How many
Two ADUs and a junior ADU
On a single-family lot: one ADU attached to or inside the house or garage, one detached ADU, and one junior ADU inside the house.
LA County Code 22.140.640.E, Table 22.140.640-ASize
Up to 1,200 sq ft
One cap for attached and detached ADUs. All four of our models fit under it.
LA County Code 22.140.640.G.1.a.ii(1)Setbacks and height
4 ft from the side and rear
Up to 25 ft tall. Where a community standards district sets a lower height, that limit applies, but a detached ADU can always be at least 16 ft.
LA County Code 22.140.640.G.1.b, G.1.c.iii(1)Fire zones
800 sq ft is still allowed
If any part of your lot is in a Very High Fire Hazard Severity Zone, state law still allows one detached ADU of up to 800 sq ft, up to 16 ft tall, with 4 ft side and rear setbacks. A larger ADU there needs the vehicle access the County requires. Model S, Model 1 and Model 2 are all under 800 sq ft.
LA County Code 22.140.640.C.1, H; Gov. Code 66323(a)(2)Parking
None outside very high fire zones
Outside a Very High Fire Hazard Severity Zone, no parking is needed. Inside one, the County asks for parking unless an exception applies, such as a half-mile walk to transit. A detached ADU of up to 800 sq ft under state law needs none.
LA County Code 22.140.640.G.1.dOwning and renting
Rent it, don't sell it separately
The County doesn't require you to live on the property to have an ADU. It can't be sold apart from the house, and a unit approved under the state's streamlined rules can't be rented for 30 days or less.
LA County Code 22.140.640.F.1, I; Gov. Code 66323(e)Changing on January 1, 2027
SB 1117 limits the impact fee on an ADU over 750 sq ft to the area above 750 sq ft, in proportion to the main house, for up to two ADUs on a lot. ADUs of 750 sq ft or less still pay no impact fee.
AB 956 lets you build two new detached ADUs on a single-family lot through the state's approval path. On that path the County can cap each one at 800 sq ft.
Sources: Los Angeles County Code 22.140.640; California Government Code sections 66310 to 66342; Executive Order N-9-25 (January 16, 2025); LA County Planning Interpretation No. 2025-04; SB 1117 and AB 956 (2026). Checked November 2026.
How it works
From your lot to move-in.
Step 1
Pick a model
Choose a model and finishes online, or book a free consultation to talk it through.
Step 2
Site assessment
We visit your lot, check utilities, access and the County's rules, including fire zone limits, and give you one all-in price before you sign.
Step 3
Design and permits
We finish the plans and run the permit with LA County from submittal to approval.
Step 4
Build and move in
We build on site and manage the job through final inspection and your certificate of occupancy.
Typical timeline: 8 to 12 months from start to finish. About 1 month of design, 2 to 4 months of permits and 3 to 5 months of construction. Your lot and the County's review times can move it.
Altadena ADU questions
What Altadena homeowners ask us.
Our models start at $165,000 for Model S, $195,000 for Model 1, $270,000 for Model 2, $360,000 for Model 3. Those are all-in starting prices for design, permitting and construction. Site work and utilities generally run $15,000 to $35,000, and we price yours after the site assessment, before you sign. County permit fees are separate: the County sets them and we bill them at cost, unless your project qualifies for the County's fire rebuild fee deferral. You start with $1,000, credited in full to your contract, and many of our clients finance the whole build through our lending partners, subject to credit approval. See what's included in the price.
Yes, if your home in unincorporated LA County was destroyed or substantially damaged in the Eaton fire. The Governor's Executive Order N-9-25 lets the ADU get its certificate of occupancy before the new house, and LA County lets your household live in that standalone ADU until January 7, 2030 while you rebuild. When the house goes up, the ADU can stay without further review. The executive order runs until January 16, 2028 unless it is ended earlier, so timing matters.
For qualifying rebuilds, yes. LA County defers and refunds its permit fees in unincorporated areas like Altadena and does not collect them later. You qualify if you owned the property and lived there on or before January 7, 2025, and the project rebuilds your home, including an ADU built as part of the rebuild, or is a standalone ADU you'll live in until the house is rebuilt. Rentals, lots owned by an LLC or corporation, and school district and utility fees are not covered. There is no deadline to apply. The County's fee deferral page has the form.
Altadena is in unincorporated Los Angeles County, so the County's ADU ordinance (LA County Code 22.140.640) and state ADU law apply. On a single-family lot you can build one ADU attached to or inside the house or garage, one detached ADU and one junior ADU, with each ADU up to 1,200 sq ft. Lots in a Very High Fire Hazard Severity Zone have extra limits. If you're not sure which jurisdiction your address is in, LA County Planning has a jurisdiction lookup on its website.
Yes. State law still allows one detached ADU of up to 800 sq ft, up to 16 ft tall, with 4 ft side and rear setbacks. A larger ADU on a lot that is even partly in the zone is allowed only if the lot meets the County's vehicle access standard, and parking can apply. We check your lot's zone and access at the site assessment.
Yes. We build across Los Angeles County and in Orange County, San Diego and the Inland Empire. In the City of Pasadena or Sierra Madre, that city's own rules and permit process apply instead of the County's, and the County's fee deferral does not. Enter your address in our quote tool to check that you're in our service area.
Rebuilding your home after the fire · More answers on our FAQ
Where we build
We also build in these cities.
Each city page covers that city's ADU rules and who issues the permit. All cities.
Los Angeles County
Orange County
San Diego County
Inland Empire
See your price for an Altadena ADU.
Pick a model and tell us your address. After the site assessment you get one all-in number, before you sign.