What is an ADU? An accessory dwelling unit is a separate dwelling on a property with a primary home or residential building. You may hear one called a backyard cottage, in-law unit or secondary unit. Those informal names do not, by themselves, establish that a space is a legally approved dwelling.
This is educational information, not design, construction, legal, lending or tax advice. California HCD and the responsible city or county provide authoritative guidance on applicable requirements.
What are attached, detached and conversion ADUs?
An attached ADU is connected to the primary building. A detached ADU is in a separate structure. A conversion ADU uses existing space, such as a garage, subject to the applicable approvals. These terms describe physical arrangements, not the cost, eligibility or permitted use of a particular project.
Is an ADU the same as a guest room or home office?
A dwelling has living facilities that distinguish it from a room used for guests or work. A floor plan or a listing description alone does not confirm its legal status. The approval and occupancy records for the property matter.
What are planning approval, building permits and final inspection?
These terms refer to different aspects of local review and construction approval. A permit is not simply a statement that a project might be possible, and an issued permit is not the same as confirmation that completed work received final approval. The responsible agency determines the requirements for the property.
What do hard costs, soft costs and a construction contingency mean?
Hard costs generally refer to physical construction, labor and materials. Soft costs generally concern items such as design, engineering, permits and financing. A construction contingency is an allowance for uncertain project costs; it is different from a purchase-contract contingency. Estimates can classify expenses differently and are not guarantees of a final price.
Is projected rental income the same as profit?
Projected rent is an estimate of income, not a guarantee of occupancy or payment. Operating expenses, financing, maintenance and other obligations are separate from gross rent. Whether an ADU can be rented, and under what terms, depends on applicable rules and the property's circumstances.
Who answers property-specific ADU questions?
Westin can discuss the real estate context. The local planning and building departments, qualified designers and contractors, lender, insurer and tax or legal professionals address questions within their roles. An ADU definition does not establish that a particular project is permitted, insurable, financeable or financially suitable.