An ADU is an additional dwelling unit that could provide affordable housing options for family members, friends, students, the elderly, in-home health care providers, the disabled, and others. In the past, an ADU was more likely to be called a granny flat in San Diego. In other parts of the country, the name “mother-in-law suite” is more commonly used. These structures are not part of the main floor plan, and they are more likely to be built as add-ons; in some cases, however, accessory dwelling unit builders are being contracted at the same time the main structure goes up. Prefab granny flats in San Diego are becoming more popular than swimming pools because they can provide an affordable housing solution. The bottom line for homeowners who hire ADU contractors is that they are looking to increase the value and utility of their properties.