A before and after shot of a house that Motzkin's converted into an accessory dwelling unit. Photo: Patricia Motzkin Architecture
Before and after shots of an accessory dwelling unit (ADU) after remodeling. Photo: Patricia Motzkin Architecture

As we know, our population is aging and more people are confronting the need to plan for appropriate living arrangements. An Accessory Dwelling Unit (ADU), either for a caretaker’s apartment or as a downsizing option, is becoming increasingly popular. The concept is not new. Commonly known as “in-law” units, these small dwelling spaces exist in a variety of forms, from basement or attic apartments to independent structures.

A major advantage of adding an ADU is that people don’t have to leave their homes. They can continue to enjoy the familiarity of their surroundings, while avoiding the emotional strain often associated with relocation later in life. Family members, friends, or a caregiver can be close at hand, living in either the main or auxiliary unit.

Under the current Berkeley Municipal Code, Accessory Dwelling Units (ADUs) are permitted. However, the requirement for a second on-site, non-tandem parking space often makes these units impossible to permit without a variance or protracted review process. As the need to build more of these units is becoming increasingly acute, to accommodate both an aging population and many families’ economic needs, it is time to remedy the planning code to facilitate their construction.

The Berkeley City Council will take up a measure Tuesday, March 24, that could go far in remedying current difficulties. I urge the council to adopt the measure put forth by Mayor Tom Bates.

It is difficult to know how many of these units already exist in Berkeley; many exist illegally, carved out of single family housing stock over the years. More people will continue to do this unless the process is streamlined to make achieving desirable goals realistic.

The benefits of an ADU extend beyond allowing residents to age in place. ADUs can enhance the neighborhood community by facilitating a diverse age range. When constructed in a controlled manner, with attention to design and scale, these secondary dwellings can increase the vibrancy of the neighborhood and provide added safety through extra eyes on the street. Usually, they are placed behind the main building, adding density without a sense of overcrowding. By reusing existing structures and utilities, rather than tearing down and constructing anew, ADUs conserve resources. Adding to their environmental friendliness is the fact that they must comply with current building codes mandating energy-efficient construction. Yet another benefit of these added units is the increased property value, as well as the potential for rental income.

What is required?

While some municipalities either do not allow these secondary dwellings or require special approvals, the Berkeley Municipal Code allows for creation of Accessory Dwelling Units by right, which means that building permits can be issued without going through the processes of neighbor notification and design review when all criteria are met. Moreover, Berkeley allows for many exceptions if the criteria cannot be met, and on March 24 the City Council will consider several important zoning amendments to further encourage these units.

The basic requirements are outlined below, with some of the proposed changes in parentheses:

  1. Gross floor area can be no more than 25% of the main house, and no less than 300 square feet if the main house is less than 1,200 square feet.
  2. Gross floor area cannot be more than 640 square feet. (This would increase to 750 square feet under the proposed new ordinance.)
  3. The owner’s lot cannot be subdivided into a separate parcel for the ADU.
  4. The lot must be on a road that meets fire truck access requirements.
  5. The ADU must have a separate on-site parking space in addition to the existing house’s spot and not in tandem. (Among the significant changes under consideration are parking waivers for units within a quarter-mile of BART and major transportation lines and allowances for tandem parking.)
  6. The owner must live in either the main house or the ADU and cannot be off the premises for more than three years.

Depending on how the ADU is created—whether as an incorporation into an existing home, an addition to an existing home, or a freestanding structure—additional criteria apply:

  1. ADUs incorporated into or added onto existing homes must have a separate, clearly defined entrance away from the front of the existing building.
  2. ADUs that are additions or independent structures must be on lots with 4,500 square feet minimum area, cannot be more than 12 feet in average height, and must conform to site setbacks, typically 20 feet at the front and rear yards and 4 feet on the sides. (Proposed changes include a new minimum lot size of 3,800 square feet, a new average height of 14 feet, and new rear yard setback of 4 feet.)

When it is not possible to meet all these criteria, the code provides for obtaining exceptions through the Administrative Use Permit process by explaining the hardship and demonstrating that the request will not adversely affect neighboring properties. This process involves drawing plans, obtaining neighbors’ acknowledgment, giving public notice, and undergoing planning department review. The process may add three to four months to the project timeline (without appeal), but an exception can be gained, given respectful design and proper discussion with neighbors ahead of time to avoid surprises.

As mentioned earlier, a common circumstance where an exception is often necessary is the parking requirement. For instance, on hillside lots and other neighborhoods, when additional parking would present a hardship both in terms of cost and in the loss of on-street parking, an exception may be granted. The pending changes in the code will eliminate the need for an AUP in many instances, which will go far in expediting the approval process and in allowing legal construction of second units.

What are some possibilities? 

Accessory Dwelling Units can be approached in different ways, with many opportunities for creativity and thoughtfulness in design. Due to their small size, 640 square feet max, every inch must count. To enhance the experience of living in a small unit, attention should be given to an efficient layout, flexible use of space, well-integrated storage and furniture, incorporation of daylight, and proximity to outdoor space.

Three ADU units recently designed by our office suggest some of the ways these additions can be adapted for different existing structures and diverse life circumstances in Berkeley. Many more possibilities for ADU design exist within the current Berkeley code.

An overview of one of Motzkin's accessory dwelling unit projects. Photo: Patricia Motzkin Architecture
An overview of one of Motzkin’s accessory dwelling unit projects. Photo: Patricia Motzkin Architecture
An overview of one of Motzkin’s accessory dwelling unit projects. Photo: Patricia Motzkin Architecture

In the first example, the owners had purchased a three-bedroom, 1,510-square-foot home near a BART station with their son. Their short-term goal was to add an affordable rental unit for their son, who works in San Francisco and lives in the East Bay. They were also thinking of the long-term potential for the home as a retirement residence for them, close to BART with caregiver accommodations.

The house, which was situated on a large flat lot, had an existing lower level with a 6-foot head height. Berkeley’s code allowed for a 384-square-foot unit. By digging down 2 feet, they were able to create a comfortable studio apartment in the back part of the house, with its own private entry patio, overlooking a large shared garden. The only issue was the requirement for a second parking space. While it would have been possible to add a second space, it would have come at the expense of garden space and a curb cut, involving the loss of one street-parking space. The owners therefore decided to request a parking waiver. They successfully argued that both the proximity to BART and major bus lines, as well as the advantages of the garden area and on street parking, outweighed the need for additional on-site parking. All the neighbors agreed to this approach. (Under the proposed new measures, the parking waiver would not be required.)

The interior of the ADU designed by Motzkin. Photo: Patricia Motzkin Architecture
The interior of the accessory dwelling unit (ADU) designed by Motzkin. Photo: Patricia Motzkin Architecture

A new entry path, with planting on either side leads to the private Accessory Dwelling Unit entrance in the rear yard, set apart with it sunken patio. A 9-foot wide entry door allows for a day-lit interior and extends the sense of spaciousness from inside the unit to the garden. The railroad kitchen is small, but highly efficient, through use of apartment sized appliances.

In another example, the owners were in their late fifties with their children grown and out of the home. They realized they no longer needed a four-bedroom, 3,000-square-foot home, yet they loved their neighborhood and did not wish to leave. They decided to downsize into a separate 640-square-foot ADU, which they could fully design to their needs. The biggest challenge was figuring out how to live with so much less space. We had long discussions about the essentials in their life, considering such questions as: “If you traveled for a year with one suitcase, what would you need?” or “If your house was on fire, what would you take?” We also looked at the aspects of living in a large home they wanted to preserve.

Through this process of questioning and reflection, coupled with an understanding the constraints of building on a hillside, we developed a plan that addressed their needs. We proposed a large, light-filled main living space, with a kitchen, seating area, desk, built-in storage, and the potential for dining with twelve. In addition to a bathroom, we suggested another small room that could double as a sleeping area and office, based on the idea of a Japanese home where spaces have multiple uses.

In this example, the uphill site constrained parking, so a parking waiver was needed. Another challenge was situating the new unit in the sloping backyard between two very large redwood trees.

In our third example, the owners had purchased a three-bedroom bungalow where they eventually plan to retire. At the moment, family members are living in the house, but the owners wish to build an ADU so that when they move in, their family members will have a separate place to live. In this case, the large flat lot can accommodate both an independent ADU and two cars parked on site, so there is no need for any special permits. Here the challenge is the small size of the existing bungalow, limiting the ADU to no more than 375 square feet. It is possible, however, to achieve a home that feels spacious and full of light within such a small space through careful placement of windows, high ceilings, and downsized appliances.

Facilitating the creation of Accessory Dwelling Units is one of the many ways in which the Berkeley City Council can help bring Berkeley into the future while maintaining its character and values. These second units allow current residents to age in place, fostering a mix of older and younger generations. They provide a means of increasing energy-efficient housing without major disruption of the neighborhood or waste of existing resources. When sensitively designed, they provide economic and comfortable accommodation for a graying population. Please support the proposed changes to the current Municipal Code.

Berkeleyside welcomes submissions of op-ed articles. We ask that we are given first refusal to publish. Topics should be Berkeley-related, local authors are preferred, and we don’t publish anonymous pieces. Email submissions to editors@berkeleyside.com. The recommended length is 500-800 words. Please include your name and a one-line bio that includes full, relevant disclosures. Berkeleyside will publish op-ed pieces at its discretion.

Patricia Motzkin is an architect in Berkeley. She established Patricia Motzkin Architecture in 1990.
Patricia Motzkin is an architect in Berkeley. She established Patricia Motzkin Architecture in 1990.