“ADU” is short for accessory dwelling unit. It is a small home that shares the lot with another home or other larger structure. It might be called a “secondary unit,” “back house,” “pool house,” “carriage house,” “in-law flat,” “mother-in-law flat,” or “granny flat.” It all adds up to the same thing, though — an extra habitable dwelling unit on a property.
Several types of ADU can be installed on a property. Examples include:
- Basement ADU (uncommon in California)
- Backyard Cottage ADU (detached from the main dwelling)
- Attached ADU (attached to the main structure)
A junior ADU, or JADU for short, is a special category of ADU defined as being 500 square feet or less, and being contained fully within the main dwelling (garage, basement, attached wing, spare bedroom, etc.)
To qualify as a JADU, it must have a separate, dedicated exterior entrance. It must also have a full dedicated bathroom and an efficiency kitchen. An efficiency kitchen is defined as a food preparation surface, storage, and cooking appliances.
In California, a detached ADU can be a maximum size of 1,200 square feet and a maximum height of 16 feet.
An attached ADU can be no more than 50% the square footage of the primary dwelling unit. For example, a 2,000-square-foot house cannot have an attached ADU larger than 1,000 square feet.
Inside, the living/bedroom area must be at least 70 square feet. The kitchen must be a minimum of 50 square feet, the bathroom a minimum of 30 square feet.
California state law stipulates no minimum lot size for the addition of an ADU. Even if you have maxed out the coverage ratio on your lot, you can still build an ADU at least 800 square feet.
California state law imposes setback requirements for new ADUs, but they have been reduced to 4’ for rear and side yards. Setback requirements also do not apply if you are converting an existing, permitted pre-existing structure into an ADU. You can even tear down the existing structure and build an ADU with the same footprint and still be exempt from those setback requirements.
If you choose to build directly up to the setback, you run the greater risk that the city inspector will require a survey. To reduce this risk, consider an extra 18 inches on top of the required setback.
Some municipalities may have a minimum building setback — meaning the distance an ADU must be placed from the primary dwelling. This varies from city to city, but it is usually either 5 or 10 feet.
You can build an ADU in your front yard if it complies with the applicable setback rules. Note that the recent reduction in setback requirements, per state law, apply to back and side yards, but not to front yards.
An ADU under 500 square feet does not require a civil engineering review (catch basins, stormwater, etc.), saving you time and money. Additionally, ADUs under 750 square feet do not incur impact fees, except for school fees. Keeping your ADU within 500-750 square feet can save you anywhere from $3,000-$5,000 or more.
According to state law, a single-family property can have up to one ADU and one JADU. A multifamily property can have up to two ADUs.
Senate Bill (SB) 9, signed into law in 2022, made it easier for certain qualifying lots to be split in an effort to ease housing shortages and increase urban and suburban density. To qualify, each parcel must be at least 40% of the original parcel’s size and at least 1,200 square feet, in addition to certain other regulations.
All other conditions being met, each newly-split lot may have one primary dwelling unit, one ADU, and one JADU. If the lot is large enough, the owner could build up to six units (two primary dwelling units, two ADUs, and two JADUs) on what used to be one big parcel.
You can, but believe it or not, starting from scratch is often cheaper and easier. Trying to convert an existing outbuilding can create extra problems—proper compaction, footings, settlement issues, outdated grading not up to current standards.
Yes. Well, not technically, but in practice yes. The ADU designation only exists in conjunction with a larger primary residence. If you have a large lot and build a small structure on it (1,200 sq ft or less, let’s say) then that will be the primary residence, with all the applicable regulations and permits.
If you want to start out with the smaller unit, build up some equity, and build a “primary residence” later, that’s a perfectly viable strategy. Once the larger structure is built, that will become the primary dwelling unit, and all ADU regulations and permits will apply to the original unit.
In other words, you must build the smaller unit to comply with both sets of regulations — primary dwelling in the first place, ADU for the future. For example, the primary residence may have to confirm with minimum size requirements per number of bedrooms, depending on municipal regulations.
Yes you can, but the city of Los Angeles and surrounding municipalities do not allow a JADU to be built inside of an ADU. The JADU must be built inside or attached to the primary dwelling.
Costs can vary, especially since the price of materials and labor can change quickly. Nevertheless, if you need a rule of thumb, go with $225-$350 per square foot.
A 750 square-foot 2bedroom/1bathroom ADU might cost around $215k to build. Add on another $20k for site costs, $8k for design work, and $8k for permitting costs, and you’re looking in the neighborhood north of $250k.
To convert a typical garage into a 400-sq-ft ADU, you’re looking at a typical cost of $90k-$100k all-in.
A number of fees that used to apply to ADUs have been waived, but some still apply. Fees to look out for include:
- Impact Fees. ADUs below 750 square feet do not incur impact fees. ADUs larger than 750 square feet will incur impact fees proportional to the size of the ADU vs. the size of the primary dwelling — typically ranging from $3k-$5k.
- Sewer Connection Fees. First-time sewer connection usually incurs fees ranging from $2k-$4k. Recurring sewer fees will run in the neighborhood of $1k. For properties that use septic systems, see below where we address that separately.
- School Fees. Typically $4/square foot, or around $2k-$5k.
Here’s a breakdown of a recent project in Los Angeles for a one story 800 sq ft. two bedroom ADU (subject to change, will vary in other jurisdictions):
- Sewer Facility Charges + Fees (LA Bureau of Engineering): $841
- Application for Building Permit + Certificate of Occupancy: $5,337.30
- LADBS Express Inspection: $367.64
- Equity Title Master Covenant and Agreement: $135
- Notary for LID + Covenant Agreement: $480
- Bureau of Sanitation Fee: $206
- Pre-Inspection Fee: $230.82
- Asbestos Report: $650
- New Building Permit Fee: $629.28
- Title 24 Fee: $200
On our first meeting or kickoff call, we will quote a high-level price based on your description of the project you have in mind. If you decide to move forward, we will present a proposal to move to Phase 1 (site plan, feasibility study), including anticipated costs for each phase of the project.
As we proceed to Phase 2 (elevation and floor planning), we will keep track of any cost implications of the decisions you make and inform you of them.
In Phase 3, we create a set of construction drawings to present to the city. After we get comments back from the city, we present you with a Guaranteed Maximum Construction Estimate (GMAX) including all anticipated costs of materials and labor.
Finally, we will present a final finish-material cost (depending on your selected finish-outs) that, when combined with the GMAX, gives you your final all-in costs. After this point, we anticipate no surprises in the pricing — unless they are pleasant surprises of lower-than-expected costs.
GoADU is happy to use plans you already have in place — if they are already pre-approved. In that case, we can quote a price exclusively for the construction.
Possibly, but we usually find that our clients don’t actually save much money, if any, by providing their own materials. Our trade agreements with suppliers enable us to provide supplies at competitive prices, and these materials have been pre-evaluated to ensure that they fit together and meet the specifications of our plans. If you want to provide your own finish materials, we can easily incorporate your selections or materials on hand to the finished ADU.
The City of Los Angeles and many surrounding jurisdictions have several publicly-available pre-approved ADU plans. You can search for these plans online, or we are happy to provide them to you to consider alongside our own pre designed plans or a customized plan. Click here to view the standard plans pre-approved by LADBS.
It can — sometimes. You may not need to go out-of-pocket for architectural plans, if you follow the plans exactly. However, you will still need to submit Title 24 calculations and a site plan. On top of that, most of the expenses in ADU construction happen in the construction and building phase, not in the design and planning phase. There’s no guarantee that a pre-approved plan won’t be more expensive to build, far outpacing the money you save up front.
We work directly with several lenders and financing providers. We can provide an array of options that may be available to you to finance the construction of your ADU.
Absolutely. GoADU can work with your lender and ensure that you have the required budget, plans, and scope of work needed for your loan application and documentation. If you don’t have contacts with construction lenders already, we are happy to put you in touch with several construction lenders we have worked with successfully.
Yes. The Fannie Mae Homestyle Conventional Renovation can be used to finance either the purchase of the property, or the construction of an ADU, or both. The loan amount will be based on the future value of the home, which may include the value added by the ADU.
As of 2021, the maximum loan available under this program is $753,250 with 85% loan-to-value for investment properties, 97% LTV for primary residences. Note that this is the value after the renovation, i.e. with the added value of the ADU.
To approve a construction loan, the lender will typically require a floor plan with elevations, a scope of work, and a budget that includes all construction costs broken down by trade (plumbing, electrical, framing, sheetrock, insulation, etc.).
The process can tend to be a lot smoother if the lender has worked with the contractor before, as the lender will be familiar with the contractor’s work and documentation, and the contractor is familiar with the lender’s requirements.
If you are purchasing new property with the intention to install an ADU, if at all possible we recommend negotiating an extended due diligence period of an extra 75-90 days to research the feasibility of the ADU, take in any site requirements, and report your ADU plan to the lender so they can order an appraisal of the property based on its estimated future value with the ADU.
Process and Timeline
From signing the proposal to the delivery of a move-in ready ADU, we’re usually looking at a turnaround time of 7-12 months. This roughly breaks down to:
- Plans and Engineering. The proposal is signed and the design process begins. We create a plan that fits your requirements and check costs against your budgetary needs. 6-10 weeks.
- Permitting. Submit the plans to the city and pull any necessary permits, working in tandem with the building department to expedite construction plans through the plan review process. 12-20 weeks.
- Construction. Within a week of obtaining the required permits and approvals, we break ground. GoADU handles the entire process, from the initial checklist to the final approval of the delivered ADU. 14-18 weeks.
If a primary single-family dwelling already exists on the property, the city is required by law to act on an application for an ADU within 60 days of receipt of the application.
Getting the necessary permits and approvals from the city can be a long and sometimes unpredictable process. The build-out process is also long and dependent on the outcome of hundreds of different decisions, with one long to-do list after another. Even minor setbacks can add up and set the project back significantly.
Yes. Once we decide to proceed with your ADU project, we can remotely measure your site to begin the feasibility process. We accomplish this by requesting data on your lot from large-scale licensed data providers. We then verify that data against public records regarding the property, as well as multiple sources of satellite imagery. This data gives us access to lot dimensions, lot square footage, building square footage, zoning, land use, and much more. With access to this information, we can assess the feasibility of your project against state and city ADU regulations with a high degree of accuracy and determine the exact position of your ADU.
The only accurate answer is “possibly.” We can formulate a plan to reduce the likelihood of incurring this extra inconvenience and expense, but ultimately it depends on the building inspector, local codes, and the site itself. Most cities don’t demand a survey for an ADU, but the final decision is in the hands of the inspector. Bottom line, we can’t promise it won’t happen, but we use our expertise and experience to reduce the likelihood that a survey will be required.
In most jurisdictions, a soils report is an optional step. If you decline a soils report, no geotechnical engineer will perform soils compaction testing on the site. We will then build the ADU to the strictest-possible UBC thresholds and design standards. If you decline a soils report, GoADU bears no responsibility for any issues that may arise from inadequate soil conditions. Opting for a soils report usually entails an extra ~$5,000.
Working with GoADU Construction
Yes! We offer a free initial evaluation, which includes some of the earliest steps in the ADU process — basic feasibility, ballpark estimate, and some details and property specifics that will help us determine whether moving forward with an ADU project is the right choice for you … and if we’re the right contractor for the project.
We start by gathering as many details as possible to give our most informed, professional opinion about the feasibility of the ADU project you have in mind. We evaluate your vision and your budget to see if they line up. We also get you set up with project management software and apps so you can seamlessly communicate with us and get status updates.
As general contractors, we provide design/build management. That means that we can be your one point of contact throughout the entire process. We manage the design, permitting, and in-field operations. We subcontract specialized trade work like concrete, plumbing, electrical, drywall, framing, tile, stucco, and HVAC. We may also partner with civil engineers, structural engineers, geotechnical engineers, and septic companies during the site-planning phase. The rest of the work we do in-house.
No — in fact, in many cases, it’s better if you don’t. Even if you have plans from another contractor or designer, we still need to go through the same process of determining the feasibility. We can even save you some money if you go with one of our “standard plans.” Otherwise, we can customize your project from the ground up. If you have sketches or a “wish list,” we can absolutely use those as our starting point. If all you have is an idea that maybe you want an ADU, that’s fine too! Don’t hesitate to reach out to us.
We serve the Greater Los Angeles area, as well as Ventura, Orange, Riverside and San Bernardino Counties. It’s a long list, so use your browser’s search function (Ctrl-S or Cmd-S) to see if your region is in our service zone. The complete list:
Los Angeles Area: Agoura Hills, Burbank, Calabasas, Canoga Park, Chatsworth, Encino, Glendale, Granada Hills, La Canada Flintridge, La Crescenta, North Hills, North Hollywood, Northridge, Pacoima, Panorama City, Porter Ranch, Reseda, San Fernando, Sherman Oaks, Studio City, Sun Valley, Sunland, Sylmar, Tarzana, Toluca Lake, Tujunga, Universal City, Valencia, Valley Village, Van Nuys, Verdugo City, West Hills, Winnetka, Woodland Hills, Alhambra, Altadena, Arcadia, Azusa, Baldwin Park, Covina, Duarte, El Monte, Glendora, Hacienda Heights, La Puente, Monrovia, Monterey Park, Montrose, Mount Wilson, Pasadena, Rosemead, Rowland Heights, San Gabriel, San Marino, Sierra Madre, South El Monte, Temple City, West Covina, Alta Loma, Bryn Mawr, Claremont, Crest Park, Diamond Bar, Guasti, La Verne, Moreno Valley, Patton, Pomona, San Dimas, Walnut, Artesia, Bell Gardens, Bellflower, Cerritos, City of Industry, Downey, Hawaiian Gardens, La Mirada, Lakewood, Long Beach, Norwalk, Paramount, Pico Rivera, Santa Fe Springs, Signal Hill, Sunset Beach, Whittier, Bell, Huntington Park, Los Angeles, Maywood, Montebello, South Gate, South Pasadena, West Hollywood, Beverly Hills, Carson, Compton, Culver City, El Segundo, Gardena, Harbor City, Hawthorne, Hermosa Beach, Inglewood, Lawndale, Lomita, Lynwood, Malibu, Manhattan Beach, Marina Del Rey, Pacific Palisades, Palos Verdes Estates, Playa Del Rey, Redondo Beach, San Pedro, Santa Monica, Topanga, Torrance, Venice, Wilmington, Mission Hills
Ventura County: Bell Canyon, Oak Park, Simi Valley
Orange County: Anaheim, Brea, Buena Park, Cypress, Fullerton, Garden Grove, Huntington Beach, Stanton, Westminster, La Habra, Los Alamitos, Seal Beach
Riverside / San Bernardino Counties: Bloomington, Calimesa, Chino, Chino Hills, Colton, Fontana, Grand Terrace, Highland, Loma Linda, Mentone, Montclair, Muscoy, Ontario, Rancho Cucamonga, Redlands, Rialto, Running Springs, San Bernardino, Upland, Yucaipa, Aguanga, Anza, Banning, Beaumont, Cabazon, Cherry Valley, Corona, East Hemet, Eastvale, French Valley, Hemet, Home Gardens, Jurupa Valley, Mead Valley, Menifee, Moreno Valley, Mountain Center, Murrieta, Norco, Nuevo, Perris, Riverside, Temecula, Wildomar, Winchester, Woodcrest, Bermuda Dunes, Cathedral City, Coachella, Desert Center, Desert Hot Springs, Indian Wells, Indio, Indio Hills, Joshua Tree, La Quinta, Morongo Valley, Palm Desert, Palm Springs, Pioneertown, Rancho Mirage, Sky Valley, Thermal, Thousand Palms, Twentynine Palms, Vista Santa Rosa, Whitewater, Yucca Valley
Our new-build ADUs are all “stick-built” construction. No manufactured homes, no mobile homes. We use a few off-site processes for speed and quality control, but most of the build is done on-site.
Yes. All work that falls within the scope of our construction agreement comes with a 2-year warranty. The warranty covers cosmetic defects that don’t arise from normal wear and tear or due to neglect or improper maintenance of the property by the owner. Our work also includes a 10-year warranty against any structural defects that can be traced to a failure on our part to follow the approved specifications and plans.
Rentals and Investments
Under state law, no newly-constructed ADU can be rented for less than 30 days. No city can overrule this law — in fact, part of the permitting process is a covenant you have to sign agreeing not to use the ADU as a short-term rental with a term of less than 30 days. What you can do, however, is relocate your primary residence to the ADU and use the pre-existing primary dwelling unit as a short-term rental, assuming no other laws or rules prohibit its use as such.
Yes. State law allows you to build up to two ADUs on an existing multifamily-zoned property with a multifamily dwelling already built on it. This includes duplex, triplex, and fourplex properties, as well as larger complexes.
The ADUs must conform to all other applicable requirements. A new standalone structure must be a maximum height of 16 feet with at least 4 feet of setback from the rear or side property boundaries.
If the property has accessory structures already in place, you can convert one of them into an ADU for every four dwelling units on the property. Examples include garages, carports, utility rooms, mechanical rooms, basements, or attics.
Some jurisdictions only allow one ADU to be built on the property if the site only has a single-family house on it — even if the site is zoned for a duplex or other multifamily zoning.
California is currently under a moratorium period for owner-occupancy requirements on ADUs. You are free to lease both the primary dwelling unit and the ADU until 2030.
It depends on where you live. Assembly Bill 1482, passed in 2019, enacts tenant protections and rent control laws throughout the state, but local ordinances may supersede that law. Generally speaking, a brand-new fully detached ADU will not fall under rent control unless it is replacing an older ADU subject to rent control. On the other hand, if the ADU is attached to a primary dwelling unit that is older than 1978, rent control laws may apply.
Other Frequently-Asked Questions
Not necessarily. If you are converting an accessory structure (like a detached garage or shed) or an existing space within the primary dwelling unit, no changes in parking requirements will apply. Even if you tear down an existing garage or carport and replace it with an ADU, this doesn’t change your parking requirements.
Additionally, if the property is located within half a mile of public transit, you do not need extra parking capacity. Finally, no extra parking is needed if you add a JADU.
If none of these exemptions apply, however, you may face changes in your required parking capacity for the property. The rule is one parking space per unit or per bedroom — whichever number is smaller.
In most cases, you do not need to run any new utilities or meters. Within your own private property, you can connect utilities “behind the curb.” If you want to track utility usage separately from the primary dwelling unit, we can install an extra submeter, at minimal cost, which will track the ADU’s consumption of electricity, water, and gas, which you can use to bill back tenants and occupants or simply keep a record.
If your property is on a septic system rather than the sewer system, we recommend an extra phase before the normal “Phase 1” of the property. In this “Phase 0,” we map your system to determine its capacity. Adding an ADU may put the current septic system over its capacity; a new system may be required. We want to make sure to factor in this cost when estimating the overall project cost.
Homeowners Associations (HOA) and Covenants, Conditions, and Restrictions (CC&Rs) are not allowed to “reasonably prohibit” a member from adding an ADU or JADU. But that doesn’t mean they can’t slow the process down, make it expensive, and even derail the process entirely if you don’t approach with care.
Some cities and jurisdictions require that an ADU match the architectural features of the primary dwelling unit. If such restrictions apply to you, we will need to price into our estimate the cost to conform with those restrictions.
If you live within an HOA, we prepare a feasibility plan, including floor plans, site plan, and elevations, which specifically address any covenants required by the city or HOA. This may satisfy the HOA. If not, you may be required to submit full construction drawings. We recommend pursuing permits and HOA approval at the same time, so feedback to both can be incorporated before we get too far down the road on the project.
If you live in a detached housing unit within a condominium association, it gets complicated quickly. The parcel is technically zoned for multifamily dwelling units, so those rules apply … but you are not the sole owner of the property. Condo owners usually own the interior of their unit, but the exterior may be considered a “common area.”
The area where you want to build the ADU may be part of a common area, maintained jointly by all the residents through their association dues. They may have a problem with you installing an ADU on the shared property for the sole benefit of yourself. Getting the association’s approval may be tricky business. It’s worth a try, but be prepared for some serious diplomacy to get the condo association to approve such a plan.
If there is no solar array on the primary dwelling unit, all new-build ADUs must be equipped with solar panels. The minimum system size to consider is around 1.44KW, starting at about $10,000. Solar panels currently qualify for a 26% Federal tax credit, but in 2023 the credit will be 22%, and then 0% for 2024.
Traditionally, an ADU may be rented out, but it could not be sold separately from the home. However, since 2022, Senate Bill (SB) 9 has opened a window for it to be possible.
SB 9 made it easier to split lots, as long as each resulting lot is no less than 40% of the original size and at least 1,200 square feet (other restrictions apply, but those are the first two big ones).
If you successfully split your lot under this provision, with the primary dwelling unit on one parcel and the ADU on another, the ADU becomes the primary dwelling unit on one of the parcels, and the parcel can be sold separately — ADU included.
Yes, for fire safety reasons, your ADU will be assigned a separate address. That way, in the event of a fire, the fire department knows exactly where to send firefighters.
Yes, it most likely will, since it adds to the value of the property. The county appraiser will conduct what is known as a “blended assessment.” The value of the land and the primary dwelling unit stay the same, while the value of the ADU is appraised and added to the property’s value. Once the new value is established, taxes will be assessed against the property based on this new value.
The new assessment process takes about a year and uses standardized “cost factors” compiled by the state, which accounts for factors like living space, garages, amenities, etc. The improvements might be set at “wholesale value” — that is, the cost of the materials wholesale. In other words, far less than it actually costs to build the ADU. Most owners see their property tax bills increase by about $1,000-$2,000.
Most likely yes. Permitting for ADUs in a coastal zone used to be difficult, but it has become much more common. The process may, however, be more time-consuming. You may need approval from a Local Coastal Program (LCP), a city-level organization tasked with handling low-impact Coastal Commission projects. LCPs have become more tolerant of ADUs, but you may face more stringent requirements based on hillside overlay zones, bluff top size, and wildland urban interface.
If you want to build a new ADU on a property that has a non-permitted (i.e. “grandfathered”) ADU or JADU already on it, you may have to reckon with permitting issues for the grandfathered ADU. Think of it as similar to bringing an unpermitted addition into compliance.
You might need to draw up a plan for the existing structure, send the plan to the city to be checked, open up the walls for the city to inspect, address any structural issues that would prevent compliance, and pay for permits. The process may cost several thousand dollars, and any tenants in the non-permitted ADU will probably have to vacate while the process is carried out.
Consider the project management process of any contractor you are considering. How much transparency and visibility does it allow for you, as the property owner? Does the contractor use technology to streamline the communication, project management, and payment process? Pick a contractor with a good reputation, one whom you enjoy working with, shares your excitement over your vision, and brings something to the table to add value to the project.
Want to start the conversation? It’s never too early! Reach out to GoADU now to discuss building the perfect ADU to add value, function, and income to your Los Angeles-area property!