Prefab ADU Builder in Altadena: New Builds and Fire Rebuilds
HCD state-approved modular ADU plans. 10-day permit pathway under AB 818 for fire-affected properties. Turnkey installation in one day.
Two Paths to a Prefab ADU in Altadena
Altadena homeowners have two paths to a new ADU in 2026: adding a prefab backyard unit to an existing property, or placing a modular home on a fire-cleared lot as part of the Eaton Fire recovery. Abodu serves both. Our plans are HCD state-approved, which means Altadena homeowners can use the state permitting pathway instead of waiting months in the LA County backlog. Under AB 818 (effective January 1, 2026), complete applications for modular housing in emergency-declared areas receive a decision within 10 business days.
Why Prefab ADUs Make Sense in Altadena Right Now
The conventional stick-built rebuild timeline in Altadena is running 18 to 24 months from permit to occupancy, with construction costs averaging $400 to $600 per square foot. A factory-built modular ADU compresses that timeline. Abodu units are constructed off-site while site preparation happens simultaneously, cutting total project duration to months, not years. Factory construction also produces consistent fire-resistance ratings that meet California's Wildland-Urban Interface (WUI) building standards, simplifying insurance underwriting in fire-affected areas.
An Abodu prefab home being craned into place on installation day.
Altadena ADU Regulations and Permitting (2026)
Altadena is unincorporated Los Angeles County. ADU permits route through the LA County Department of Regional Planning and Building and Safety. Abodu's HCD state-approved plans can bypass local plan review entirely, compressing the permitting timeline from weeks to days.
Size and Height
ADU Size Limits in Altadena
Detached ADUs can be up to 1,200 square feet. Attached ADUs are limited to 1,200 square feet or 50% of the primary dwelling, whichever is smaller. Junior ADUs (JADUs) are capped at 500 square feet. Detached ADUs are limited to 25 feet in height. Two-story ADUs are allowed; stacked ADUs are not. Single-family lots may add one detached ADU, one attached ADU, and one JADU.
Permitting Timeline
How Long Does an ADU Permit Take in Altadena?
Standard plan check through LA County takes approximately 4 to 6 weeks. However, Abodu's HCD state-approved plans can use the state permitting pathway, bypassing local plan review entirely. Under AB 818, complete applications for modular housing in emergency-declared areas receive a decision within 10 business days. Abodu handles all permitting for your prefab ADU from start to finish.
Fire Rebuild Pathway
Rebuilding After the Eaton Fire in Altadena
The Eaton Fire (January 7, 2025) destroyed over 9,400 structures across Altadena. If your home was destroyed, Abodu's HCD-approved modular units qualify under AB 818 (10-day permit decision) and AB 462 (ADU occupancy before primary dwelling is rebuilt). Confirm your lot clearance status with LA County Public Works, then contact Abodu to start the process. Your unit is factory-built while your foundation is prepared on-site.
Financing
Altadena ADU Financing and Grants
The CalHFA ADU Grant Program provides up to $40,000 for eligible homeowners to cover pre-development costs including site preparation, permits, soil tests, and impact fees. LA County has waived certain permitting fees for fire-affected properties. Many Altadena homeowners finance ADU construction through a home equity line of credit (HELOC) or cash-out refinance. Abodu's fixed-price contracts make it straightforward to present lenders with a clear project budget. Learn more about financing your prefab ADU.
FAQs: Prefab ADUs in Altadena
How long does it take to get an ADU permit in Altadena?
How long does it take to get an ADU permit in Altadena?
Standard plan check through LA County takes 4 to 6 weeks. However, Abodu's HCD state-approved plans can use the state permitting pathway, which bypasses local plan review. Under AB 818 (effective January 1, 2026), complete applications for modular housing in emergency-declared areas receive a decision within 10 business days.
Can I build an ADU on my fire-cleared lot before rebuilding my main home?
Can I build an ADU on my fire-cleared lot before rebuilding my main home?
Yes. Under AB 462 (effective October 10, 2025), an ADU can receive a Certificate of Occupancy before the primary dwelling is rebuilt in counties with declared emergencies. This allows families to move back onto their Altadena property while the primary home is still under construction or being planned.
What is the maximum ADU size allowed in Altadena?
What is the maximum ADU size allowed in Altadena?
Detached ADUs can be up to 1,200 square feet. Attached ADUs are limited to 1,200 square feet or 50% of the primary dwelling size, whichever is smaller. JADUs are capped at 500 square feet. All four Abodu models fit within these limits.
Does Altadena allow short-term rentals in ADUs?
Does Altadena allow short-term rentals in ADUs?
No. Altadena does not permit ADUs to be used for stays of 30 days or fewer, including Airbnb. ADUs in Altadena are intended for long-term occupancy or rental use only.
How much does a prefab ADU cost in Altadena?
How much does a prefab ADU cost in Altadena?
Abodu models start from $228,800 (Studio, 340 sq ft) and range up depending on model and site conditions. All pricing includes permitting, site work, and installation with a fixed-price guarantee. No hidden fees. Visit our pricing page for current details.
Get your free Altadena site assessment.
Ready to add a prefab ADU to your Altadena property or start your fire rebuild? Abodu provides full end-to-end service, including HCD-approved permitting, site work, factory construction, and one-day installation. Schedule a call or visit our showroom today.
HCD state-approved plans.
10-day fire rebuild permitting.
One-day installation.
Fixed-price guarantee. No hidden fees.
Find your new Abodu in Altadena.
