What drives the cost of building an ADU in Los Angeles County

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Two ADUs of the same size can cost very different amounts. This page lists what moves the number, so you can read a bid and ask good questions. It gives no price, because a fair price comes from a written scope for your lot.

Does the type of ADU matter?

Yes. A garage conversion, an attached unit, a detached new building and a second-story unit are different jobs. A conversion reuses a foundation and walls, so less is new. The existing structure still has to be brought up to what the plans require.

A detached unit needs its own foundation, structure, roof and utility runs. In any type, kitchens and bathrooms do more to the cost than floor area does.

How does my lot change the cost?

Slope, soil, access and what is already on the site all affect the work. A hillside lot may need a deeper foundation, grading or retaining walls as part of the building project. Trees, an old slab or buried lines can add work before the first wall goes up.

Why do utilities matter?

Electrical service, water, gas and the sewer connection are often where the surprises are. Ask how far the new unit is from each connection. Ask whether the existing service has room for the added load.

The location and capacity of the sewer line can affect both the work and the timeline. Find out early what the local agency requires. A new electrical panel or a longer pipe run can change the number.

Who pays for plans and engineering?

Plans, structural calculations, energy compliance documents and sometimes a soils report are separate from construction. They come from designers, engineers and other outside professionals. They are usually contracted and paid for separately from the building contract.

A complete set of plans also gives you bids you can compare. Every bidder prices the same drawings.

What fees should I expect?

Plan check, permits and inspections carry fees. Utility connections and some other agency charges can apply. State law limits some fees on smaller ADUs, and the rules have changed in recent years. Ask the building department for the fee list that applies to your unit. Ask each builder whether fees are in the bid or left for you to pay directly.

Do fire rules add cost?

Fire access to the unit, and in some cases fire sprinklers, depend on the lot and on the department that reviews it. Ask early what applies to your property. It is far cheaper to learn at the plan stage than after the walls are closed.

How much do finishes matter?

This is the part you control most directly. Flooring, cabinets, counters, tile, fixtures, windows and doors range widely. An allowance is a set dollar amount for a finish item. A bid with allowances is telling you how much of the price is a placeholder.

Choose and price your finishes before you sign. Then the allowances stop causing change orders.

Why do changes cost more later?

Trade availability and material prices move, and a long schedule costs more than a short one. A change made after work starts nearly always costs more than the same choice made on paper. Sign a change order before the work is done. Then both sides are clear on what changed and what it costs.

How do I compare bids?

Put the bids side by side. Check what each one includes:

• Are they pricing the same plans?
• Which fees, utility connections and site work are in the bid, and which are left to you?
• What are the allowances? Are they realistic for what you want?
• What is left out, in writing?
• What is the payment schedule? Does each payment follow completed work?
• Is the contractor's license active on the CSLB site?

The lowest number is not always the lowest cost. A bid that leaves out the sewer work or the fees will look cheaper until those items arrive.

Where does EMC fit?

EMC Development Solutions Corp prices every job from a written scope, and the scope comes before the number. We do not prepare plans. They come from the owner's designer, architect or engineer. When we build a project, the building inspections, through final, are part of the construction contract.

EMC Development Solutions Corp is a private building contractor. This page is general information. It is not a publication of the City of Los Angeles, Los Angeles County or the State of California, and it is not legal advice.

Learn about our ADU builder work in Los Angeles County, or contact us about your ADU.