Los Angeles ADU Planning and Construction Guides

This page organizes the choices behind an ADU building quote. It does not offer design or building work. It helps Los Angeles homeowners find missing items before they share project details or sign a contract.

If you are asking “Can I build it?”

Start with the ADU property check. That guide covers the items below.

• City of Los Angeles, another city or unincorporated Los Angeles County;
• assessor and parcel details;
• zoning, existing units and planned ADU type;
• setbacks, building separation and usable site area;
• slope, drainage, fire, coastal, historic and other overlays;
• access for construction and long-term occupancy;
• electrical, water and sewer questions; and
• the records to obtain before design fees grow.

A company can help investigate these points, but its sales estimate is not a government approval.

If you want a new backyard unit

Read the detached ADU construction guide. A new unit needs a full building plan. This includes the survey, site plan, foundation and frame. It also includes weather protection, energy rules, building systems, finishes, inspections and outside work.

A detached ADU can work well when the site has enough room, good access and a sound utility plan. It may be a poor first choice when site work drives the cost. Examples include grading, retaining walls, fire access, protected trees or long utility runs.

If you have an existing garage

Read the garage conversion ADU guide before assuming the garage is a low-cost shell. The inspection and plan should address the items below.

• permit history and measured footprint;
• slab condition and finished-floor strategy;
• wall and roof framing;
• moisture, termite or decay evidence;
• ceiling height and openings;
• fire and sound separation;
• plumbing route and sewer fall;
• electrical service and new loads; and
• whether replacement would produce a clearer result.

Conversion saves only the work that can genuinely remain.

If the unit will connect to the house

The attached ADU and JADU guide separates three paths that owners often confuse.

1. a new attached addition with independent living facilities;
2. an ADU converted within current habitable or accessory space; and
3. a JADU contained within a qualifying single-family structure.

Do not compare price alone. Privacy, daylight, fire safety, sound and shared walls all matter. So does the effect on the main home.

If you are choosing drawings or a permit strategy

Use the ADU design and permits guide for the filing steps. It shows why the address and permit office must match the plans. The survey, building design, structure, Title 24 forms and utility details must also agree.

Then compare standard plans, prefab and custom design. “Pre-approved” often applies to the plan, not the site. A custom plan may cost more to design. It can make sense when a standard plan does not fit the property.

If utilities or access are unclear

Read the ADU utilities and site-work guide. It covers the power panel, water, sewer and drainage. It also covers demolition, grading, trenches, equipment access and repairs.

Utility and external work should appear as named quote rows. A phrase such as “connections included” is too broad for a six-figure project.

If you need a realistic budget

The 2026 Los Angeles ADU cost guide uses public prices only as a planning aid. They are not fixed market prices. The guide shows the budget items needed to compare two totals.

Do not compare a shell price with a price that includes design, permits, utility upgrades, appliances and repairs after the work. Ask each company to mark items as included, allowance, owner-supplied, provisional or excluded.

If you need to schedule the project

The ADU construction timeline shows what must happen before each stage can start. It separates site checks, design, plan review and utility work. It also covers orders, site work, the build, inspections and final approval.

The schedule should state who owns every submission and what event starts the next stage.

If you are comparing builders

Use the builder comparison guide after the design is clear enough to price. It includes the checks below.

• CSLB license and entity checks;
• directly relevant completed-project evidence;
• work and allowance normalization;
• permit and utility duty;
• subcontractor and supervision questions;
• payment milestones and change-order control;
• written warranty and final approval documents; and
• current workload and start-date evidence.

CSLB advises owners to compare written quotes using the same drawings, product details and scope. This site requests one project introduction and does not promise a fixed number of responses.

Location and city or county guides

Use the Los Angeles-area service guides when the site is outside the City of Los Angeles. Use them if the permit office is unclear too. Long Beach, Pasadena, West Hollywood and unincorporated County areas have their own permit systems.

A location guide does not mean a company is ready to take the job. It helps settle the local permit path before an inquiry is sent.

What to send with a project inquiry

Provide the city and ZIP code. Share the street address only if you are comfortable doing so. Add details about the main home, garage, ADU type, size, access, budget and timing. Include any survey, assessor record, old plans or utility notes you have.

Do not send financial account details, identity documents or unnecessary tenant details through an initial website form.