What Is an Accessory Dwelling Unit?
In California, an accessory dwelling unit (ADU) is defined as a self-contained residential unit located on the same lot as an existing single-family home. It must be smaller than the primary residence and include all the basic amenities of a functioning home — a kitchen, bathroom, sleeping area, and storage space. While ADUs are sometimes referred to as in-law suites, granny flats, or casitas, the key distinction is that they function as a fully independent living space, separate from the main residence.
Fassino Development works with homeowners looking to build ADUs on their existing properties, guiding them through the process from planning to completion as an experienced ADU contractor.
Why Consider Building an ADU?
There are several practical reasons homeowners choose to add an accessory dwelling unit to their property:
- Additional income: An ADU can serve as a rental unit, providing a supplemental income stream without the need to purchase a separate investment property.
- Simpler than traditional real estate investment: Buying additional land or investing in a multifamily property comes with significant complexity and cost. Building an ADU on existing land avoids many of those complications.
- No land purchase required: Since the unit is built on property the homeowner already owns, there is no need to navigate the often lengthy and expensive process of finding and purchasing a new parcel of land.
- Privacy and proximity for family: For homeowners who want to house an aging parent or family member nearby, a detached ADU offers the independence of a separate living space while keeping family members close.
As an ADU builder, Fassino Development helps homeowners evaluate which of these goals best fits their situation and what type of build makes the most sense for their property.
What Can Be Built and What Are the Requirements?
The allowable size of an ADU varies by location, but as a general guideline in California, a homeowner may build up to 50% of the primary home's square footage or up to 1,200 square feet — whichever is smaller. It is worth noting that this rule can differ from one city or county to another, which is why working with a knowledgeable ADU contractor from the outset is important.
Beyond square footage, there are additional requirements that typically apply:
- Setback and height requirements based on local zoning regulations
- Parking requirements, which often mandate at least one off-street parking space
Each municipality has its own specific code requirements, and navigating these details without proper guidance can lead to delays or costly revisions. Fassino Development brings familiarity with local regulations to each project, whether it involves a backyard cottage, a garage conversion, or a granny flat builder project tailored to a homeowner's specific needs.