An Accessory Dwelling Unit (ADU) is a fully self-contained residential unit built on the same lot as a primary home. It has its own entrance, kitchen, and bathroom and can be detached, attached to the main house, or converted from an existing garage or interior space.
In California, ADUs are fully legal on nearly every single-family and multifamily lot. State law has made them faster to permit, harder for local agencies to block, and one of the smartest ways a California homeowner can add housing, generate rental income, or accommodate family all without leaving their property.
ADU stands for Accessory Dwelling Unit a fully independent residential unit built on the same lot as a primary home, with its own entrance, kitchen, and bathroom. In California, ADUs can be detached, attached, garage conversions, or Junior ADUs (JADUs). Per the California HCD, all ADUs require a permit before construction begins.
A Junior ADU (JADU) is the most affordable option built entirely within your home’s existing footprint with no new foundation required. Garage conversions are the next most cost-effective route since the shell and foundation are already in place. Contact Greenport for a free estimate tailored to your property.
ADU costs in California are driven by high labor rates, strict Title 24 energy compliance requirements, and soft costs like permits, architectural drawings, and utility connection fees. The Harvard JCHS notes that California’s regulatory environment pushes soft costs well above the national average. Working with an experienced builder who submits complete permit packages the first time helps keep the project on budget.
Yes, every ADU in California requires a building permit, no exceptions. Under AB 2221, local agencies must approve or deny a complete application within 60 days. Building without a permit risks fines and makes the unit illegal to rent or sell.
The main drawbacks are the upfront investment, a construction timeline of 9–18 months, and permitting complexity that varies by city. Some properties also require utility upgrades to support a second unit. Most California homeowners find the long-term benefits rental income, added housing flexibility, and increased property value outweigh these challenges.
Most California homeowners can build at least one ADU and one Junior ADU (JADU) on their property — regardless of what local zoning says. California state law, updated by AB 2221 and SB 897, overrides most local restrictions that previously made ADU construction difficult or impossible.
If you own a single-family home in California, state law generally entitles you to one detached ADU and one JADU on the same lot. Multifamily property owners can add ADUs equal to 25% of their existing unit count. Minimum lot size requirements have been eliminated statewide for most zones, and local agencies are prohibited from denying a permit based solely on lot coverage or floor-area ratio as long as the ADU meets state minimums.
A few situations can add complexity: properties in historic districts, coastal zones, or those with active deed restrictions may require additional review steps. But these rarely disqualify a project entirely they just mean a more careful approach upfront. At Greenport, we pull your parcel data, review your local ordinances, and flag any site-specific issues during the free consultation. You’ll know exactly what’s possible on your lot before committing to a design or a budget.
As affordable ADU builders serving all of California, Greenport builds all four ADU types permitted under state law — from fully custom ADU homes to straightforward garage conversions. The right choice depends on your lot, your budget, and what you need the space to do.
A fully standalone structure built separate from the main home, with its own foundation, utilities, and entrance. Up to 1,200 sq ft. Offers maximum privacy and the highest rental potential the top choice when lot space allows.
Added as an extension of the primary residence, sharing at least one wall. More affordable to build than a detached unit while still delivering a fully independent living space with its own entrance, kitchen, and bathroom.
Transforms an existing attached or detached garage into a livable unit. Uses the existing structure and foundation, which significantly reduces construction complexity. California law does not require you to replace the parking removed for a garage conversion ADU.
Created entirely within the existing footprint of the primary home most commonly from a bedroom or interior garage space. Capped at 500 sq ft, a JADU must include an efficiency kitchen and a separate exterior entry, but may share a bathroom with the main residence.
California has some of the most homeowner-friendly ADU laws in the country here are the key rules that apply statewide.
Every Greenport ADU follows a structured five-step process designed to minimize delays, keep you informed at every stage, and get your Certificate of Occupancy as fast as the law allows.
We visit your property, pull your parcel data, and review the local ADU ordinances that apply to your specific lot. We discuss which ADU type fits your goals, walk you through realistic timelines, and answer every question you have with no obligation and no sales pressure.
Our licensed architects produce plans that comply with California Title 24 energy standards, your city’s design guidelines, and the specific setback and height limits for your lot. You review and approve all drawings before anything is submitted to the city no surprises.
We submit a complete permit package to your local building department and manage every round of plan-check corrections. Under AB 2221, agencies have 60 days to approve or deny a complete application. We track the clock, follow up proactively, and handle all correspondence so the process doesn’t stall.
Our licensed crews handle everything from site prep and foundation to framing, roofing, insulation, mechanical, electrical, plumbing, drywall, and finish work. You get a dedicated project manager and regular progress updates so you always know where your build stands.
We schedule and pass all required inspections framing, rough MEP, energy compliance, and final and secure your Certificate of Occupancy. Once issued, your ADU is fully legal, insurable, and ready to occupy, lease, or list as an ADU for rent near you.
Schedule your free consultation in California’s Bay Area with Greenport Construction Inc. We help homeowners plan and execute remodeling and construction projects with clarity, precision, and care—making the process smooth from the very first step.
Complete the form below and use the Message field to briefly describe your project goals, timeline, and priorities. Whether you’re planning a kitchen remodel, home renovation, or custom construction, your input allows us to tailor our approach to your home and location within the Bay Area.
Our team will promptly contact you to arrange a complimentary on-site consultation, where we’ll review your space, discuss scope, answer questions, and outline next steps. If you already have plans or drawings, we’ll coordinate seamlessly and provide a free, detailed estimate.
Phone: (415) 413-0038
Email: services@greenconstruction.info
Schedule your free consultation today and take the first step toward a well-planned Bay Area California home.
