What an ADU Costs in Los Angeles

The honest answer depends on which of two very different projects you mean. Across 16,424 finaled ADU permits in the City of Los Angeles, the median construction valuation declared on the permit is $45,000 for a garage or interior conversion and $110,000 for a new detached unit. Those are the city’s own records, not an estimate.

Read the rest of this page before you use those numbers. Declared valuation is a real figure from a real permit, and it is not what a builder will quote you. The gap is explainable, and the section below explains it.

One number for two different products

The figure usually quoted for Los Angeles is a single citywide median across every ADU permit, which is $65,000 here. It is accurate and it answers almost nobody’s question, because it blends a garage conversion with a new detached house in the backyard. Split them and the difference is roughly 2.4x: a conversion declares $45,000 at the median, a new build $110,000. Conversions are the more common of the two in Los Angeles, which pulls the blended median down toward the cheaper project.

The quartiles matter as much as the medians. Half of new detached builds declared between $79,000 and $135,000, so a single median hides a spread wide enough to contain two quite different builds.

What declared valuation leaves out

Declared valuation is the value of the construction work as entered on the permit application. The building department uses it to compute plan check and permit fees. That is its whole job, and it is why it is a reliable way to compare thousands of real projects against each other and an unreliable way to budget one.

It does not include:

• Design fees, including the architect and the engineer
• Permit and plan check fees themselves, which are computed from this number
• Utility connections and any service upgrade
• Site work: grading, drainage, trenching, landscaping
• Finishes and fixtures beyond what the permit describes
• The contractor’s overhead and profit

Against those medians, put two real budgets A-du has published, which are Dwell’s figures as the posts say: $89,430 for a detached unit in Highland Park whose owner acted as his own architect and contractor, and $220,722 for a studio built over a rebuilt garage. Both are delivered costs of finished units. The first sits close to the declared median for a new build; the second is roughly double it. That range is the honest answer to “what will mine cost”, and where a project lands inside it is decided by who does the work, what the site needs, and the finish level.

The permit layer is the one part of this you can compute exactly rather than estimate. A-du’s ADU permit fee calculator itemizes building permit, plan check, sub-permit, state surcharge, school and impact fees for the City of Los Angeles, unincorporated LA County and ten more LA County cities, with the code citations and the waivers that apply under 750 square feet.

Per square foot

Across 14,240 finaled permits carrying both a valuation and a plausible ADU square footage, the median declared valuation is $105 per square foot, with the middle half between $78 and $136. The same exclusions apply: this is the declared construction value divided by the permitted area, not a builder’s price per square foot.

For scale, the median finaled ADU in Los Angeles is 620 square feet, so the median unit and the median rate describe roughly the same project.

By neighborhood

The ZIP codes that have finaled the most ADUs, with the median declared valuation in each. These are the places where the most owners have actually completed one, which makes them the places with the most comparable work nearby.

Read these as a mix, not a price map. A ZIP that builds mostly conversions will show a lower median than one building mostly new detached units, and that difference is about what is being built there rather than what it costs to build there.

Common questions

How much does it cost to build an ADU in Los Angeles?

Across 16,424 finaled ADU permits in the City of Los Angeles, the median declared construction valuation is $45,000 for a garage or interior conversion and $110,000 for a new detached unit. Declared valuation is the value of the work entered on the permit and used to compute building department fees; it excludes design fees, permit fees, utility connections, site work and finishes, so treat it as a floor rather than a quote. A-du's published project budgets, which are Dwell's figures, run from $89,430 for a detached unit whose owner acted as his own architect and contractor to $220,722 for a studio built over a rebuilt garage.

Is a garage conversion cheaper than a new detached ADU?

On the permit record, substantially. The median declared valuation is $45,000 for a conversion against $110,000 for new construction, and conversions are the more common of the two in Los Angeles. The foundation, walls and roof already exist in a conversion, which is where the difference comes from. It is not automatic: an older garage may need a new slab, new footings, drainage or a full re-roof, and utilities usually have to be run in from scratch.

What is the cost per square foot of an ADU in Los Angeles?

The median declared valuation works out to $105 per square foot across 14,240 finaled permits that carry both a valuation and a plausible ADU square footage, with the middle half falling between $78 and $136. This is a declared figure, not a builder's price per square foot, and the same exclusions apply: no design fees, permit fees, utility connections, site work or finishes.

Why is the permit valuation lower than what builders quote?

Because they measure different things. Declared valuation is the value of the construction work as entered on the permit application, and the building department uses it to compute plan check and permit fees. A builder's price is the delivered cost of the finished unit and includes design, permitting, utility connections, site work, finishes, overhead and profit. Declared valuation is useful for comparing one unit type against another across thousands of real permits, which is exactly what this page does with it, and it is not a substitute for a bid.

What do ADU permit fees cost in Los Angeles, on top of construction?

Permit and plan check fees are a separate layer from the construction valuation, and they are computable rather than estimated. A-du publishes a free calculator that itemizes building permit, plan check, sub-permit, state surcharge, school and impact fees for the City of Los Angeles, unincorporated LA County and ten more LA County cities, with the code citations and any waivers, including the impact fee waiver under 750 square feet.

Where does this cost data come from?

From the City of Los Angeles building permit export published by LADBS as Open Data. The figures aggregate every permit classified as an Accessory Dwelling Unit whose Certificate of Occupancy has been issued, 16,424 of them, and are regenerated from source. Nothing on this page is modeled, estimated or imputed, and the methodology section states what is excluded and why.

Method, and what is excluded

Every figure above is computed from the City of Los Angeles building permit export published by LADBS as Open Data. The query selects permits whose use is Accessory Dwelling Unit and whose status is Certificate of Occupancy issued, so every permit counted describes a unit that was actually finished and inspected. Permits are deduplicated on permit number.

The per-type, per-ZIP and per-square-foot figures exclude permits whose recorded square footage is above 1,200 square feet, which is the state cap for a detached ADU in Los Angeles. A row above it is reporting a whole-building or whole-project area, and those rows carry whole-project valuations that would inflate any like-for-like comparison. 1,249 permits were excluded on that basis. The citywide median of $65,000 across 16,415 permits does not carry that guard, deliberately: it is the one broad figure, and it is the same number published on the Index.

Work type is classified from the permit’s own description text by the same routine the rest of A-du uses, so a conversion is a permit that describes converting existing space. Nothing here is modeled, estimated or imputed, and no figure is derived from a field the permit does not carry.

For the full aggregate behind these numbers, including how many units were finaled each year, the conversion and new-construction split, unit sizes and the complete ZIP table, see the LA ADU Index.

Generated September 22, 2026 from Los Angeles Department of Building and Safety — Building Permits (Open Data). Regenerated monthly from source.