As San Jose, California continues to grow, many high-end residents are exploring options for expanding their homes. Two popular choices for home expansion are Accessory Dwelling Units (ADUs) and home additions. While both offer the benefit of additional space, there are distinct differences between the two that residents should consider before deciding which option is best for them.

ADU Vs Home Additions

An ADU is a separate living unit within an existing home or on the same property. ADUs can be built above garages, within existing homes, or as standalone structures, such as a tiny home or converted garage. They provide the owner with additional living space while also generating rental income, making them a popular choice for many San Jose residents.

Home additions, on the other hand, involve adding additional space to the main home. This can include adding rooms, expanding existing rooms, or even building an entirely new level onto the home. Home additions are often chosen by residents who want to expand their living space without having to move to a new home.

Permit Requirements for ADUs and Home Additions in San Jose, California
One of the biggest differences between ADUs and home additions is the permit requirements for each type of expansion. In San Jose, California, the permitting process for ADUs is typically less complicated than for home additions. This is because ADUs are generally smaller in scale and do not require as much structural work as home additions.

To build an ADU in San Jose, residents need to obtain a building permit, as well as a planning permit if the ADU will be a standalone structure. The city also requires that the ADU comply with all zoning and building code requirements, including requirements for parking, setbacks, and access.

The permitting process for home additions is more complex, as these expansions often involve significant structural work to the main home. In addition to a building permit, residents may also need to obtain a planning permit, a grading permit, and a site development permit.

Furthermore, home additions in San Jose often require additional inspections, such as electrical, plumbing, and mechanical inspections, as well as fire safety and handicap accessibility inspections.

Cost Comparison: ADUs Vs Home Additions

Another important factor to consider when deciding between an ADU and a home addition is cost. The cost of building an ADU in San Jose can vary depending on the size and type of unit, but generally ranges from $100,000 to $200,000. This cost typically includes the cost of construction, permits, and materials.

In contrast, home additions can be significantly more expensive, with costs ranging from $200,000 to $500,000 or more. This is because home additions often require more extensive work, such as adding new foundations, walls, and roofing, as well as upgrading existing electrical, plumbing, and HVAC systems.


Both ADUs and home additions offer high-end residents in San Jose, California the opportunity to expand their homes and increase their living space. However, the differences between the two options, including permit requirements and cost, should be carefully considered before making a decision.

ADUs may be the better option for residents who want to add additional living space to their home with a lower level of hassle and expense. Home additions, on the other hand, may be the better option for residents who want to make larger structural changes to their homes and are willing to invest more time and money into the process. Ultimately, the choice between an ADU and a home addition will depend on each resident’s individual needs and goals.