While many cities in California limit ADU construction to one story, there are no such restrictions at the state level. If you are located in one of the cities that doesn’t have restrictions on ADU height, there are some things you should consider if you want to build a second story on your ADU. It may not be in your best interests to include that second layer.

Cons of Adding a Second Story

Adding a second floor to your ADU is not always a good idea. Here are some reasons you may not want to do it:

  • Square footage limitations: The second floor of an ADU still counts towards the overall square footage limit of the space. However, the stairs leading to the second floor will take up a great deal of the space and largely be a waste. You can store things beneath the stairs, but they take away from the living area.
  • Increased cost: The second floor can be more expensive per square foot than the first. Running utilities up, choosing a layout that supports a second story and building stairs all increase costs.
  • Design limitations: Your first floor will need to be designed to support the second, which may put constraints on the floor plan, particularly an open floor plan.
  • Stairs: Many ADUs are intended to be used as granny-flats or spaces for older family members to live. In this case, stairs are a huge hurdle that can limit the function of the space. Even if you do not intend to use the ADU for this yourself, the person buying your home may. You may get a better value for an ADU that is just one story tall.

Pros of Adding a Second Story

For some people, adding a second story to their ADU is a great decision that can even help them maximize the size of it. Here are some benefits of including that second story:

  • Lot size limitations: Some local building codes require you to leave a certain percentage of green space on your lot. Sometimes building a two story ADU with a smaller footprint can allow you to stay within these guidelines while still maximizing square footage.
  • Aesthetics: Many people prefer the look of two-story ADUs. They may work better with your current architecture and help keep the curb appeal of your overall structure.
  • Privacy: Not everyone likes having a bedroom on the first floor of a space. Especially considering ADUs are so small and may be flanked by the living space of the main home too, you may want to place the bedroom on a second floor to increase feelings of privacy.

If you can’t decide whether the pros of adding a second story to your ADU outweigh the cons, we suggest you speak with a professional designer.

What About a Third Story?

Technically, yes, California law allows you to build a three story ADU. However, they also require you to bring an architect on board for the project. Most people find that a three-story ADU is costly and impractical, especially as ADUs are so small. You will likely want to stick to a one-story ADU.

If you are searching for an ADU builder in Berkeley, get in touch with us today.