Understanding Accessory Dwelling Units (ADUs)

An Accessory Dwelling Unit (ADU) is a secondary residential structure on a single-family lot. Configured as detached, attached, or internal units, ADUs comprise independent living quarters with kitchen and bath facilities.

Often termed "granny flats" or "in-law suites," they serve as versatile property enhancements. Beyond accommodating family or generating rental income, ADUs offer flexible spaces for guests, home offices, or personal pursuits. As such, they augment property value while contributing to broader housing solutions.

Everything About ADU's

You've got questions, and we have answers. From understanding the basics of ADUs, granny flats, and casitas to navigating the complex world of permits and costs, we'll guide you through the process. Let's demystify ADUs together. Discover essential terminology and California's ADU regulations to get started on your ADU journey.

Common ADU Terminology Explained

What distinguishes an ADU from a guest house? Is a granny flat synonymous with an ADU? You've likely encountered a plethora of terms for Accessory Dwelling Units (ADUs). From the classic "granny flat" to the more formal "secondary living unit," the nomenclature is vast. While "additional," "auxiliary," or "accessible dwelling unit" are common misconceptions, the accurate term is Accessory Dwelling Unit. Regardless of the label, ADUs offer versatile living spaces.
Junior Accessory Dwelling Units (JADUs) are smaller, internal units that can be added to an existing single-family home. Unlike traditional ADUs, JADUs must be contained within the main residence, such as a converted garage or spare bedroom. Limited to 500 square feet (with a possible 150-square-foot addition for access), JADUs include a full bathroom and kitchenette. Both ADUs and JADUs require the property owner to reside on the property.
While often conflated, ADUs and guest houses are distinct. Guest living quarters are specifically designated for temporary occupants, such as employees or visiting guests, and lack essential amenities like kitchens and laundry facilities. In contrast, ADUs are designed for long-term habitation and include full living accommodations. Importantly, San Diego County permits only one of these options per property.
California now recognizes tiny homes as a form of Accessory Dwelling Unit (ADU). These compact homes, ranging from 150 to 430 square feet and requiring DMV registration, can be placed in backyards as standalone units. Importantly, a tiny home ADU replaces, rather than supplements, a traditional ADU. To qualify as an ADU, tiny homes must be fully connected to utilities and situated on a concrete pad. Due to these requirements, the overall costs of a tiny home ADU often mirror those of a permanent ADU.