ADU, conversion & addition questions, answered.

An accessory dwelling unit is a self-contained second home on a lot that already has a house — its own kitchen, bathroom, and private entry. It can be detached in the backyard, attached to the house, built above a garage, or converted from existing space such as a garage or an unused portion of the house.

California state law allows up to 1,200 sq ft for a detached ADU, or up to 50% of the main house's footprint, whichever is greater. Los Angeles has adopted the state maximum. Your own maximum depends on your lot and local ordinance, which we confirm during feasibility.

A junior ADU is created inside the existing house — commonly 300–500 sq ft — with a private entry and an efficiency kitchen. Because there is no new foundation, it is usually the least expensive way to add a separate living space, and the bathroom may be private or shared depending on the design.

State law no longer requires owner-occupancy for ADUs built through 2029, so both units can be rented. Local rules vary, so we confirm your specific city's ordinance before design.

For most detached ADUs in Los Angeles no additional off-street parking is required, particularly within a half mile of transit. Because this varies by jurisdiction and location, we confirm it for your specific lot.

Yes. A matched ADU reuses the same stucco, roof tile, and trim so it reads as a smaller version of the main house. A contemporary approach — flat or mono-slope roof, larger windows, modern finishes — is equally common. Both are design choices, not cost tiers by themselves.

Generally yes, because the slab, walls, and roof already exist. The cost is driven by insulation, egress, plumbing runs, and whether the electrical panel has capacity. A detached unit costs more but adds new square footage rather than repurposing existing space.

A garage becomes a dwelling through insulation and finished surfaces, a compliant window and door for light and egress, plumbing and drainage for a kitchen and bath, heating and cooling, and electrical work that the existing panel can support. Those items, not the square footage, are where the work lives.

Converting the garage means giving up that enclosed parking. Some homeowners pair a conversion with a new detached garage elsewhere on the lot; others accept driveway parking. It is worth deciding before design rather than during construction.

Yes. An interior conversion turns underused space — a large bonus room, a basement area, part of a floor plan — into a separate living unit with its own entry. It avoids new foundation work entirely, which is why it is often the fastest conversion path.

An ADU is a separate, independently rentable home and can be refinanced and rented as such. A room addition expands the house you already live in and does not create a second unit. The right answer depends on whether you want rental capability and separation, or more space inside your own home.

Often yes, but a second story depends on the existing foundation and framing, so structural engineering comes early rather than late. It is the most involved addition type because the work touches the whole house, and it is scoped during design before pricing is committed.

A kitchen expansion typically means moving or removing walls, relocating plumbing and electrical, upgrading ventilation, and integrating the new footprint with the rest of the floor plan. Structural work is common whenever a load-bearing wall is involved.

The addition needs to work with the existing structure and roof lines, and matching materials is the most common approach. A deliberate contrast can also work when it is designed rather than accidental.

Yes. We prepare the permit set — architectural drawings, structural engineering, Title 24 energy compliance, and MEP plans — submit for plan check, respond to corrections, and pull the permit in your name. You approve; you do not stand in line.

Under state law, cities must approve or comment on ADU applications within 60 days. Most departments comply. We use that clock to keep the process moving and to hold the reviewing agency accountable.

It depends on your address. Incorporated cities run their own building departments and fee schedules, while unincorporated parcels are reviewed by the county — LA County, OC Public Works, or Ventura County RMA. We confirm the reviewing agency and its current requirements during feasibility, because rules and fees vary by jurisdiction and site.

Feasibility and site walk first, then design, then construction documents and engineering, then plan check and permits, then construction, then final inspections and handoff. The process page walks through each stage in detail.

Most detached ADUs finish in roughly 7–10 months on site once permits are in hand, with design, engineering, and plan check happening before that. Conversions and smaller additions are typically shorter. Your actual schedule depends on design complexity and the reviewing agency's queue.

The ranges published on this site are preliminary planning ranges, not quotes. Every project's price depends on design, jurisdiction, site conditions, utilities, and finishes. HomeAdd provides a detailed construction proposal after feasibility and design rather than a fixed price sight-unseen.

Because a responsible number requires knowing what is being built and where. Slope, utility capacity, fire-zone status, protected trees, and which agency reviews the permit all move a budget, and none of them are visible from a phone call. Feasibility first, then design, then a detailed proposal.

Hard costs are construction — foundation, framing, mechanical, electrical, plumbing, finishes, and any site work such as retaining or drainage. Soft costs are design, structural engineering, energy compliance documentation, permit and plan-check fees, and any utility or district fees that apply. A complete budget includes both.

Line up the scope item by item: design, engineering, permits, utility work, site work, and finishes. Check whether site work is priced rather than assumed, and look closely at finish allowances, since low allowances get spent through quickly. An incomplete proposal is not a cheaper one.

Many homeowners use a HELOC, a cash-out refinance, or a construction loan, and some lenders offer ADU-specific products that consider future rental income. We can refer you to specialists; HomeAdd is not a lender.

Yes. The cost estimator produces a preliminary planning range from the configuration you describe, which is a useful starting point before a site walk.

HomeAdd is headquartered in Woodland Hills and builds across Los Angeles County, Orange County, and Ventura County — including the San Fernando Valley, the Westside, the South Bay, and the Conejo Valley.

One project manager stays with the project from design through handoff, with weekly walkthroughs and photo updates. Design, engineering, permitting, and construction sit under one contract, so there is a single point of contact rather than coordination between separate firms.

We look at your property and what you want to build, review setbacks, utilities, and zoning, and tell you honestly what is buildable. The project qualifier collects the details we need for that first answer, and HomeAdd typically responds within one business day.

Applicable warranty terms are documented in the signed contract, along with the project closeout package.