What are ADUs?

Accessory Dwelling Units (ADUs) have been known by many names: granny flats, in-law units, backyard cottages, secondary units and more. No matter what you call them, ADUs are an innovative, affordable, effective option for adding much-needed housing in California. HCD is the state’s leader on local ADU ordinances, which — while optional — have grown exponentially in number as more cities, counties, and homeowners become interested in ADUs as one solution to increasing the supply of affordable housing.

What are the benefits of ADUs?

  • ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators.
  • ADUs can provide a source of income for homeowners.
  • ADUs are built with cost-effective wood frame construction, which is significantly less costly than homes in new multifamily infill buildings.
  • ADUs allow extended families to be near one another while maintaining privacy.
  • ADUs can provide as much living space as many newly-built apartments and condominiums, and they’re suited well for couples, small families, friends, young people, and seniors.
  • ADUs give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care.

What are JADUs?

Junior Accessory Dwelling Units (JADUs) are allowed to be created within the walls of a proposed or existing single-family residence and shall contain no more than 500 square feet. JADUs offer additional housing options. They may share central systems, contain a basic kitchen utilizing small plug-in appliances, may share a bathroom with the primary dwelling, all to reduce development costs. JADUs present no additional stress on utility services or infrastructure because they simply repurpose existing space within the residence and do not expand the dwellings planned occupancy.

New! New laws effective January 1, 2020

The Legislature further updated ADU and JADU law effective January 1, 2020 to clarify and improve various provisions in order to promote the development of ADUs and junior accessory dwelling units (JADUs). These include allowing ADUs and JADUs to be built concurrently with a single-family dwelling, opening areas where ADUs can be created to include all zoning districts that allow single-family and multifamily uses, modifying fees from utilities such as special districts and water corporations, limited exemptions or reductions in impact fees, and reduced parking requirements. Please see the Accessory Dwelling Unit Technical Assistance memo (PDF) for more information.

Master plan submittal package

An accurate, complete submittal package is required and must include:

  1. Architectural information, plans, elevations, sections, and details
  2. Structural information, plans, elevations, sections, and details
  3. Structural calculations
  4. Title 24 energy documents, as applicable
  5. Truss plans and calculations, as applicable
  6. Indication of Fire sprinklers: Provide a statement as to whether the standard construction plan layout proposes to be equipped with an automatic fire sprinkler system.
  7. Geotechnical investigation report, as applicable
  8. For ADUs, you may use code minimum soil valuation for foundation design, or pre-scripted footing sizes if conventional construction is used, or match existing foundation.
  9. A standard site plan as reference is optional.
  10. ADUs are a secondary dwelling unit with complete independent living facilities for one or more person. They are an innovative, affordable, effective option to increase the value and space of your home. Today ADUs are known by different names: granny unit, granny flat, in-law unit, in-law cottage, mother-in-law apartment, sidekick home, laneway home, backyard guesthouse, backyard cottage or secondary dwelling unit. ADUs are affordable in California as they do not require paying for land, major new infrastructure, structured parking, or elevators. Further can provide an additional source of income for homeowners.
  11. What is JADU?
  12. A Junior ADU (or JADU) is a new category of dwelling units created by the State of California. The main difference is that a JADU is not required to have a dedicated bathroom.
  13. Architectural Plans for ADUs
  14. The first step of creating an ADU is to have an architectural plan. If you do not have a plan handy, we are happy to connect you with one of our trusted Architect partners in your area. Our partner architects specialize in various architectural styles and can create an Architectural Permit set for any design styles you have in mind.
  15. Engineering Services for ADUs
  16. We have you completely covered when it comes to the engineering required for the ADU. Our engineers can take your ADU vision and iron out the details to ultimately create the ADU plans for construction. We then work with you across the ADU construction and oversee every step of the project.
  17. What’s are the steps to building an ADU?

Start with Design. You can work with a drafter, designer or architect to start designing the ADU. Talk about your options to build within an existing building (most of the time this is the cheapest option), or look at building a new structure. We have done a few designs (interior, detached, above garage, and garage conversions) see below for some inspiration. We help clients from the very beginning stages of planning and researching, all the way to creating construction plans for permits. We do remote design as well. Give us a call or email for more information on ADU design.

Next step is Permits: Visit your city’s Planning and Building Department to learn the rules, pick up forms and ask about fees. Experienced professionals definitely make the process easier. We can help you with research as well as submitting plans for you as your authorized agent.

After permits, is construction. Get detailed bids from several contractors, call their references and check their licenses with the state. Get a written contract that lists all costs and details up front to avoid expensive changes later. Communicate frequently and verify progress before making payments. Working with an outsourced project manager can ensure you have an owners representative that is verifying construction progress and reviewing progress payment requests for you. We provide Design Led Project management services to clients that we drafted and designed for. We help you gather bids for construction, review bids and over all project costs, as well as provide sub contractor scheduling and weekly on site visits to ensure project timeline progress and design details are being met.

How much do ADU’s cost to build?

Below are some general cost estimates we have gathered:

  • Internal ADUs can sometimes be built for about $50,000
  • New detached ADUs often exceed $150,000
  • Most ADUs are financed through some combination of savings, second mortgages, renovation loans, home equity lines of credit and/or funds from family members (sometimes a relative who ends up living in it).

What are the basic guidelines for an ADU?

New state laws have made it easier than ever to build a second unit in California. Check with your local building and planning department for specific codes for your area. Below are general guidelines when planning an ADU:

  • Typically they can be no larger than 1200 SF.
  • Range from 1-2 bedrooms
  • Include kitchen or kitchenette, bathroom, and sleeping space
  • If within 1/4 mile from public transit, no additional parking is required
  • May not require interior fire sprinklers
  • Do not require separate utilities. If you decide to do secondary utilities discounted rates are available for ADU projects.
  • Some government agencies allow a second ADU if one of the homes on the property meets accessibility standards.

Build an ADU on your property- design guide

What is an ADU? ADU stands for Accessory Dwelling Unit. This is a secondary housing unit much like the term “granny unit”. ADU’s are independent living space, an ADU is self-contained, with its own kitchen or kitchenette, bathroom and sleeping area. Many areas in California have a housing shortage. ADU’s are an innovative, affordable, and effective option for adding much-needed housing in California.

There are many benefits to adding an ADU to your property. An ADU can provide rental income to homeowners and an affordable way for renters to live in single-family neighborhoods. They can become a space for family members to live so they are near by but also have an independent living space. For homeowners looking to downsize, an ADU can be a more appealing option than moving into an apartment or, if older, an age-restricted community, and allows older residence to age in place.

ADU’s can be built in many different ways; Detached, Attached, as part of the interior of the home like a lower or upper level, above a garage, or converting a garage.

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