Question 1

What is the difference between an ADU and a home addition?

Accepted Answer

An ADU (accessory dwelling unit) is a self-contained living space with its own kitchen, bathroom, and entrance — designed to be rented or used as a separate residence. A home addition adds square footage to the main house (a bedroom, family room, or second story) that's connected to the existing living space. ADUs follow California's streamlined permitting pathway with 60-day approval timelines; additions follow standard building permits. If your goal is rental income or multi-generational housing, an ADU is the answer. If your goal is more living space within the main home, an addition is the right choice.

Question 2

What should I know before building an ADU?

Accepted Answer

Before investing in architectural plans, evaluate setbacks (how close you can build to property lines), lot coverage limits, height restrictions, zoning, and whether the lot can accommodate utility connections. California state law has overridden many local restrictions for ADUs — but local rules still apply to height, setbacks, and parking in some cases. A feasibility study should come first so you know what's possible and what it will realistically cost before committing to design.

Question 3

How does the ADU permitting process work in California?

Accepted Answer

California's ADU law (Government Code §65852.2) provides a streamlined ministerial approval process — meaning the city must approve or deny an ADU application within 60 days, without discretionary review. This is dramatically faster than a standard building permit, which can take months of plan check and design review. For home additions, standard permitting applies, including neighborhood design review in some cities.

Question 4

How are utilities handled for an ADU?

Accepted Answer

An ADU needs its own electrical panel (or a sub-panel), water and sewer connections (or a separate meter in some jurisdictions), and gas if applicable. Trenching for utilities, connecting to the main service, and coordinating with the utility company are often the most time-consuming parts of an ADU project. This hidden complexity should be scoped early in the design phase.

Question 5

Do I need engineering for a home addition?

Accepted Answer

Yes. Any addition that changes the home's footprint, height, or structural load requires a structural engineer's stamped plans for permit submission. This includes foundation design, load path calculations, and the structural tie-in to the existing home. For a second-story addition, the engineer must verify the existing foundation and walls can support the new load — sometimes requiring foundation reinforcement.

Question 6

What should I look for in an ADU or addition contractor?

Accepted Answer

Verify a valid California contractor's license, confirm insurance, and ask whether they handle the full scope — architectural design, structural engineering, Title 24 energy modeling, permitting, utility coordination, and construction. A design-build team that manages all of this under one contract reduces coordination risk and schedule overruns. Ask for references from recent ADU or addition projects and confirm they coordinate the structural tie-in to the existing home so the new foundation doesn't settle differently.

Question 7

What professionals may be involved in an ADU project?

Accepted Answer

A typical ADU project may involve a general contractor, architect or designer, structural engineer, Title 24 energy consultant, civil engineer (if grading or drainage is needed), soil engineer (if the geotechnical report requires a specialized foundation), and utility company coordinators. The general contractor manages all of these professionals under one contract in a design-build model, reducing the homeowner's coordination burden and schedule risk.

Question 8

What happens during ADU construction?

Accepted Answer

Site prep and grading come first, then foundation excavation and pouring, then framing and the structural tie-in, then rough plumbing, electrical, and HVAC, then insulation and drywall, then exterior finishes and roofing, then interior finishes, cabinetry, and fixtures, and finally final inspection and certificate of occupancy. Utility connections (electrical panel, water, sewer, gas) are coordinated with the utility company throughout. A detached ADU typically takes 4–8 months of active construction depending on size, complexity, and weather.

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