About ADU Garage Experts
ADU Garage Experts is a structural engineering firm based in Southern California, specializing in the planning and drafting of accessory dwelling units (ADUs). Operating as a dedicated division of Peter Erdelyi & Associates, the company brings together structural engineers, drafters, expeditors, and project staff to help property owners plan and execute ADU projects.
The firm was established in response to the growing demand for ADUs across Southern California. Their team's experience extends beyond residential ADU work, covering projects ranging from home conversions to large-scale commercial buildings. ADU Garage Experts also works with a network of trusted contractors to help carry construction through to completion on schedule.
What Is an Accessory Dwelling Unit?
An Accessory Dwelling Unit (ADU) is a residential dwelling unit located on the same lot as an existing primary residence. The state of California defines it as an attached or detached unit that provides complete independent living facilities, including provisions for living, sleeping, eating, cooking, and sanitation.
There are three main types of ADUs:
- Converted ADU: The conversion of a previously non-livable space — most commonly a garage — into a livable unit. Estimated cost is approximately $100–$150 per square foot, with a typical timeline of 4–6 months.
- Attached ADU: A portion of the existing primary dwelling is converted into a separate living space with its own entry. Up to 50% of the primary dwelling can be converted. Estimated cost is around $200 per square foot, with a timeline of 9–12 months.
- Detached ADU: A separate, standalone structure built on the property — often referred to as a guest house, granny flat, or backyard cottage. Also estimated at approximately $200 per square foot, with a timeline of 9–12 months.
ADUs are also commonly known as granny flats, in-law suites, casitas, or mother-in-law suites, depending on the context and configuration.
Why Build an ADU and What Does It Cost?
There are several practical reasons property owners choose to build an ADU. These include generating rental income, creating additional living space for family members, or simply increasing the overall value of the property.
One of the more cost-effective options is a garage conversion. Because a garage already has an existing structure and foundation, the cost is considerably lower than new construction. In Los Angeles, the average cost for a garage conversion is approximately $70 per square foot, compared to around $200 per square foot for standard residential construction. As an example, converting a 400 square foot garage at $70 per square foot would cost around $28,000, while potentially adding up to $198,000 in property value.
Common uses for ADUs that ADU Garage Experts has helped clients build include:
- Rental space for additional income
- Short-term rental units (e.g., Airbnb)
- Home offices or business spaces
- Guest houses or detached ADUs
- Living quarters for family members or assisted living
- Game rooms, home gyms, or artist studios
From a broader perspective, ADUs also carry economic, environmental, and social benefits. They make use of existing infrastructure, have a smaller environmental footprint than new single-family construction, and provide additional housing options in residential neighborhoods without significantly altering neighborhood character.
To qualify for an ADU in California, a property generally must be located in a single-family residential zone, have an existing house on the lot, and meet applicable construction and site requirements. Parking requirements may also apply, though exceptions exist for properties near public transit or those with existing accessory structures.
Most homeowners finance their ADU conversion through a home equity loan. ADU Garage Experts is available to discuss financing options and help determine whether a given property qualifies for an ADU project.
