Alto Builders

About Alto Builders and ADU Construction in Los Angeles & Ventura County

Alto Builders specializes in the design and construction of Accessory Dwelling Units (ADUs) in Los Angeles and Ventura County. They work with homeowners who are considering adding a secondary dwelling unit to their property, guiding them through the process from initial planning to completed construction.

An ADU — also referred to as a granny flat, casita, in-law suite, backyard cottage, or guest house — is a secondary housing unit located on a residentially zoned property. These units typically include a full kitchen, a bathroom, and a private entrance. They can be used for multigenerational living, rental income, guest accommodations, or as a home office or studio space.

Alto Builders works with several types of ADU configurations:

1. Detached ADU — A stand-alone structure built separately from the main home, offering fully independent living space.
2. Attached ADU — An addition or expansion connected to the existing home structure.
3. Garage conversion — An existing garage or non-habitable space converted into a functional living unit.
4. Junior ADU (JADU) — A smaller unit, typically within the existing home, allowed on single-family properties alongside a standard ADU.

Understanding ADU Regulations in California

California has passed several laws over the past few decades to make ADU development more accessible. These laws set a baseline that local municipalities must follow, though some cities — including Los Angeles — have adopted additional ADU-friendly policies.

Key points under current California ADU law include:

1. There is no minimum lot size requirement for ADUs.
2. Local governments must allow at least an 850 sq. ft. one-bedroom or 1,000 sq. ft. two-bedroom ADU with only 4-foot side and rear setbacks.
3. An 800 sq. ft. ADU must be permitted by right, even if it exceeds floor area ratio limits or encroaches on front setbacks.
4. Many impact and development fees have been waived or reduced.
5. Owner occupancy requirements have been permanently removed, allowing ADUs on rental properties.
6. HOAs and CC&Rs cannot impose unreasonable restrictions on ADU development.
7. Most parking requirements have been eliminated for ADUs within half a mile of public transit or car share services.
8. Building departments are required to respond to ADU applications within 60 days.

In California, single-family properties may add both an ADU and a Junior ADU. Multifamily properties can add ADUs up to the number of existing units, with a maximum of eight starting in 2025 under SB 1211. In the City of Los Angeles, additional units may be possible through the ADU Bonus Program.

Despite statewide regulations, each municipality retains its own specific requirements. Alto Builders helps clients navigate these local rules to avoid delays and additional costs during the permitting process.

ADU Costs and Project Timelines

The cost of building an ADU in the Los Angeles and Ventura County areas typically ranges from $300 to $600 per square foot, depending on the type, size, finishes, and site conditions. For a turn-key detached ADU between 500 and 1,200 sq. ft., budgeting between $350 and $500+ per square foot is a reasonable starting point.

Alto Builders provides the following base pricing as a general reference:

1. Garage conversion ADU: $120,000 base (includes first 400 sq. ft.) + $300/sq. ft. additional
2. New build ADU: $140,000 base (includes first 400 sq. ft.) + $350/sq. ft. additional
3. Above garage ADU: $150,000 base (includes first 400 sq. ft.) + $375/sq. ft. additional

Additional costs may include blueprints and plans, finish materials, appliances, and hardscaping. Factors such as foundation requirements, utility connections, and design complexity can also affect the final budget.

In terms of timeline, the full process of designing, permitting, and building a new ADU typically takes between 5 and 12 months. The design phase generally takes 1–2 months, permitting and plan check takes 2–8 months, and the construction phase takes approximately 3–5 months depending on the size and jurisdiction.

Alto Builders works as an ADU contractor serving homeowners across Los Angeles and Ventura County, offering guidance on design, permitting, and construction with a focus on transparent pricing throughout the process.