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ADUs might help with affordable housing but codes needed

Apr 03, 2022 07:25PM ● By Bill Hardesty

A garage to apartment conversion is one type of ADU. (Courtesy of

By Bill Hardesty | [email protected]

The idea of Accessory Dwelling Units (ADU) as one solution to the affordable housing crisis is a discussion topic at many levels of government.

The South Salt Lake Community Development staff recently presented an ADU tutorial to the South Salt Lake Planning Commission and floated some code ideas.

The basics

An ADU is a secondary housing unit on a single-family residential lot. There are two types of ADUs—internal and external.

An internal ADU must be attached to the primary residence. Internal ADUs are common and within code. Examples are an over-the-garage apartment, a basement apartment, or a converted garage into an apartment.

“There’s the internal accessory dwelling unit, which is located within the footprint of the dwelling,” Sean Lewis, deputy director of community development, said. “The primary residence must be owner-occupied. We want to have long-term renters in there. They are a permitted use in any area zone and must comply with building and fire and health codes.”

External ADUs are detached from the primary residence. External ADUs are the affordable housing solution hot topic. The common argument is that ADUs could provide rental income to help pay the high cost of current mortgages or provide flexible living spaces for multigenerational households or could help increase the market value of available dwellings.

They are more than a “she shed” in the backyard, but not by much. An ADU must have a kitchen and a bathroom. In addition, an external ADU must be permanently attached to city services, including sewer. Currently, no state standards leave cities to determine ADU code.

Floating code ideas

One area the Community Development staff looked at was lot size. They determined that an external ADU might be difficult on 6,000-square-feet or less lot using common planning principles.

“We found that 6,000-square-feet or below lot size probably is a little bit too small for an external accessory dwelling unit because you can’t fit the dwelling unit and parking space on the property,” Lewis said.

It might not be easy to have an external ADU based on the current code in the city’s northeast corner. However, they could have internal ADUs. The study also showed that the city’s southeast corner could easily have an external ADU because of bigger lots.

“We don’t want to target any one neighborhood for the externality user or say that’s the only place they can go. So, we need to come up with some reasonable standards as to how to put these throughout the city,” Lewis said.

He mentioned two concerns over smaller lots. One is parking. Often smaller lots only have 11-foot driveways that only fit one or two cars and have a little area to walk around the vehicles. Another concern is access for fire apparatus. Firefighting vehicles would have to park in the street and pull hoses to the back ADU in smaller lot areas.

In the presentation, the staff showed good and bad code ideas. For example, one is to have at least 10 feet between the structures.

Another is a design principle. The Community Development staff talked about how the ADU design should complement the primary residences and the neighborhood. Think of a primary home with rectangle windows, gray siding with white trim, a pitched roof, with an external ADU with round windows, blue siding with dark blue trim and a flat roof. The ADU looks out of place.

Another big issue with ADUs is parking. The Community Development staff would like driveways that provide enough off-street parking for both dwellings. However, in reality, this isn’t likely. Instead, ADUs will increase street parking. It is essential to remember that street parking in front of a residence is public parking and cannot be controlled by the resident.

Size is another issue. Should a two-story external ADU be allowed when the primary dwelling is not? Or, depending on the placement of a two-story ADU, a person could look into a neighbor’s backyard or even their home.

Next steps

There are no code proposals before the planning commission or the city council. The city staff is still formulating ideas. Staff waited for the end of the legislative session just in case the state mandated anything, which they did not. The city staff is open to thoughts from residents.