ADU construction (backyard units and garage conversions)
Detached, attached and garage-conversion accessory dwelling units, built to current state rules.
An ADU is a second, self-contained home on a lot that already has a house: a detached backyard unit, an attached addition, or a converted garage. We build ADUs under CA License #1020290 from your plans.
Under California Government Code section 66317 (formerly section 65852.2, amended by AB 68 in 2019), a city or county must approve or deny a complete ADU application within 60 days when a home already exists on the lot, and local standards may not rule out an ADU of at least 800 square feet with 4-foot side and rear setbacks. Local rules still apply for design, utilities, fire access and association rules, so what fits on your lot is decided parcel by parcel (California HCD ADU guidance).
Signs an ADU is a good fit: space in the yard or an underused garage, a relative who needs a place, or a wish for rental income. A job runs from lot survey and plans through permits, utilities, slab, framing, systems, inspections and final. Utility connections and trade work such as electrical and plumbing are done by licensed trade partners where a specialty class is required.
Published ranges, not quotes. Angi lists ADU builds at $60,000 to $285,000 (average $180,000, national); HomeGuide lists $50,000 to $150,000 for a 500 sq ft unit, at $100 to $300 per sq ft (both national; checked 2026-11-11). Angi notes California permit costs of about $10 to $12 per sq ft. Local utility fees and site work can move the total.
Common questions
How long does the city have to review an ADU?
State law (Government Code section 66317, formerly 65852.2 as amended by AB 68) sets 60 days from a complete application. The agency has 15 business days to say whether the application is complete, so a full plan set matters.
Can I build an ADU in a homeowners association?
State law limits how an association can prohibit ADUs, but associations can still set design rules. Read your CC&Rs and ask the association before drawings are final.
Where we do this work
ADU construction (backyard units and garage conversions) in Carlsbad
Additions, ADUs and rebuilds in Carlsbad, with city permits and a coastal-zone check.
ADU construction (backyard units and garage conversions) in Escondido
Home additions, ADUs and fire or water rebuilds for Escondido's older housing stock.
ADU construction (backyard units and garage conversions) in Encinitas
Additions, ADUs and whole-home work in Encinitas, with coastal and design-review checks.
ADU construction (backyard units and garage conversions) in Del Mar
Careful additions and rebuilds in Del Mar, where design review and the coastal zone shape every project.
ADU construction (backyard units and garage conversions) in Oceanside
Additions, ADUs and reconstruction in Oceanside, from coastal bungalows to inland tract homes.
ADU construction (backyard units and garage conversions) in Carmel Valley
Room additions and renovations in Carmel Valley's newer, HOA-governed neighborhoods.
ADU construction (backyard units and garage conversions) in Leucadia
Additions and rebuilds for Leucadia's small coastal lots along Highway 101.
ADU construction (backyard units and garage conversions) in Rancho Santa Fe
Additions and rebuilds in Rancho Santa Fe, where County permits and the Association's Art Jury both apply.
ADU construction (backyard units and garage conversions) in Cardiff
Additions and renovations for Cardiff-by-the-Sea's small lots near the lagoon and the coast.
ADU construction (backyard units and garage conversions) in Olivenhain
Additions, ADUs and rebuilds on Olivenhain's larger semi-rural lots.
ADU construction (backyard units and garage conversions) in Fallbrook
Additions, ADUs and fire or water rebuilds in Fallbrook's unincorporated rural neighborhoods.
ADU construction (backyard units and garage conversions) in Fairbanks Ranch
Additions and rebuilds in Fairbanks Ranch, with association design review on top of County permits.
ADU construction (backyard units and garage conversions) in Rancho Bernardo
Additions, renovations and fire or water rebuilds for Rancho Bernardo homes west of I-15.
ADU construction (backyard units and garage conversions) in Solana Beach
Additions and rebuilds in Solana Beach, one of the oldest housing stocks in North County.
ADU construction (backyard units and garage conversions) in Vista
Additions, ADUs and rebuilds for Vista's older neighborhoods, from the city core to the east side.
ADU construction (backyard units and garage conversions) in La Costa
Additions and ADUs in La Costa, a master-planned part of Carlsbad with HOA and city review.
ADU construction (backyard units and garage conversions) in 4S Ranch
Additions and ADUs in 4S Ranch's newer neighborhoods, under County rules and HOA approval.
ADU construction (backyard units and garage conversions) in Rancho Penasquitos
Additions and renovations for Rancho Penasquitos' 1960s to 1980s family homes.
ADU construction (backyard units and garage conversions) in San Marcos
Additions, ADUs and rebuilds in San Marcos, from older tracts to newer hillside neighborhoods.
ADU construction (backyard units and garage conversions) in San Elijo Hills
Additions and ADUs in San Elijo Hills, a master-planned part of San Marcos with HOA review.
ADU construction (backyard units and garage conversions) in Bonsall
Additions, guest houses and fire rebuilds on Bonsall's rural lots.
ADU construction (backyard units and garage conversions) in North County San Diego
What to expect for building and rebuilding across North County: which office permits what.