How Much Does It Cost to Build an ADU?

How Much Does It Cost to Build an ADU?

How much does an ADU cost?

That is inevitably the first question you'll ask when considering a new ADU.

I do not blame you; that would be the first question I would ask as well. There is no reason to spend time and money designing and planning an ADU that is going to be too expensive to build, or too expensive to afford.

An ADU will cost anywhere between $80,000 and $350,000+ depending on the size and design of the ADU.

The final ADU cost is determined by factors such as the type of ADU being built (Attached vs Detached vs Garage Conversion), the accessibility of the building site, and the quality of material specified.

And with cost in mind I thought I'd take a few minutes and help you understand a typical ADU budget, and even provide a real world cost breakdown for a custom detached ADU I recently built in the City of Los Angeles.

Modern ADU in Los Angeles

Keep in mind that all construction projects are unique, and cost will vary depending on the size of ADU you want to build and the quality of construction you desire.

ADU Construction Cost Budget

The following cost breakdown is for a 650 sqft detached ADU.

This small backyard home is what I would describe as custom with many nice upgrades. The building was designed to be ultra-efficient with an air-tight building envelope and insulation well above code requirement.

Upgrades like rift white oak kitchen cabinets and vaulted ceilings in the main living area added to the build cost but gave the finished ADU a very luxurious feel.

The details that follow are for a new detached custom ADU in or around Los Angeles. It covers everything from initial design and planning, to city permits, to hard construction costs and issuance of the Certificate of Occupancy (CofO).

Line Item Cost Comments:
Design & Structural Engineering $12,000 The budget included design fees to Cali ADU for the ADU Design and Structural Engineering. Fees also covered energy modeling per State of California Title 24 requirements, and a storm water drainage plan by the Civil Engineer.
Building Permits $8,500

All fees required to plan and build the ADU through the City of Los Angeles. Fees included Los Angeles Department of Building and Safety ($), City of Los Angeles Fire Department to verify there was a fire hydrant close by ($), City of Los Angles Bureau of Engineering ($), and City of Los Angeles Storm water ($).

For more detailed information about the cost of an ADU permit in Los Angeles, click here.

Site Prep / Excavation $7,000 ADU was built in a backyard that was almost completely flat and required no demolition of any existing structures and very little site prep. This fee covered the trenching on the foundation footings and preparation of the building pad. Also included the hauling of the spoils (i.e. - dirt) that were removed when we trenched the footings.
Site Drainage System & Rain Harvesting $9,000 All new construction in Los Angeles requires that any rain that falls on the roof (or other impermeable structures) must be retained on-site and treated. This requires rain barrels to collect all roof run-off and a filtration system to treat the rainwater before it is used for landscaping on sent to the city storm drain.
Concrete Foundation $19,500 Our Structural Engineer designed a slab-on-grade foundation for the ADU due to the flatness of the backyard. Our footings were in expansive soil so they needed to be a little deeper than usual, but overall the foundation was relatively inexpensive and easy to build.
Rough Carpentry $26,000 Standard 2x6 walls and 2x12 roof joists were used and the amount of structural beams were kept to a minimum to keep the costs of the rough framing relatively low.
Stucco $14,500 A smooth "Santa Barbara" stucco siding finish was used on the exterior which gives the home a modern, luxurious feel.
Roofing $12,000 A high quality asphalt shingle "cool roof" was installed to match the roof of the existing home. The roof comes with a 30 year warranty and looks fantastic!.
Windows & Exterior Doors $9,500 We used Milgard Ultra Series fiberglass casement windows throughout the ADU. The fiberglass windows are a great choice for durability and longevity.
Plumbing $24,600 This covered all the rough and finish plumbing and plumbing fixtures for the ADU, but it also included connecting the ADU to the city sewer and taping into the city fresh water lines.
Electrical $21,500 The ADU is set-up with its own electrical meter and panel, so the ADU can be rented and the renter can pay for their energy usage separately from the main house. Due to the age of the existing electrical panel on the front house the city required that we upgrade the existing panel as part of the project which added money to our budget for electrical.
HVAC $7,200 A super-efficient mini split HVAC system was designed and installed for the ADU.
Insulation $8,500 The Title 24 requirement for energy efficiency are already pretty high in the State of California, but we decided to increase the efficiency of our ADU even more by adding 2" of continuous insulation to the exterior of the walls and roof. This additional insulation cost a little more but will improve the comfort in the ADU substantially.
Drywall & Interior Paint $11,500 A Level 5 drywall finish was applied to interior walls of the ADU. A Level 5 finish (for those of you unaware) is a full skim coat finish which gives the walls a completely smooth finish. It is the highest level of finish available and gives the ADU a luxurious wall finish.
Interior Doors $3,800 Solid wood interior doors were used throughout the ADU. In such a small home it is important to use solid wood to reduce sound transfer and noise throughout the home.
Millwork (Base & Case) $4,750 Nothing too special here. Just traditional solid wood base and case around the floors, doors, and windows. Expertly installed and finished of course!
Kitchen Cabinets $9,500 Solid rift white oak kitchen cabinets were used and look awesome! White oak is a very popular choice for high end kitchens and baths and for good reason. It provides a warm natural look and will last a lifetime.
Flooring $6,500 Luxury Vinyl Plank (LVP) flooring was used as it is a very beautiful and long lasting flooring option.
Tile & Stone $9,750 We opted for a beautiful marble for both the kitchen and bath vanity tops. And the shower and bathroom floor we're tiled with hand made cement tiles for an earthy finish.
Appliances $6,800 A Bosch apartment size appliance package was installed for this ADU. Great appliances that are well proportioned for the space.
Total $232,400  

So, there you have it. This is just one example of what an ADU costs in Los Angeles. I know a lot of you are getting your calculators out to see what the cost per square foot price is for this ADU. After all, that is how we are taught to determine whether we are getting a good deal when building our new home.

ADU Cost Per Square Foot

I will save you a few seconds of work; the price was approximately $358 per sqft, which is a little on the high side compared to many ADUs we build. But it is in-line with what you can expect to pay for a well-designed and built home.

I would caution you that calculating the cost-per-square-foot for an ADU can be misleading. You must remember that this is a (small) custom home that is designed and built unique for you and your backyard.

And the ADU comes equipped with a full-size kitchen and full-size bathroom within its modest footprint.

Kitchens and bathrooms are expensive to build on a cost-per-square-foot basis, and for this reason you never get a bid from a builder that states the cost-per-square-foot for kitchens and baths.

Since the ADU is small it simply does not benefit from the same economies of scale that larger homes do. There are no large living room or additional bedrooms that are relatively inexpensive to build as compared to a full-size kitchen.

A better way to look at the cost of a new detached ADU is to think in terms of the value it is creating. In many neighborhoods in Los Angeles a new 650 sqft ADU will add $300,000+ to the resale value of the home, which is a phenomenal investment.

But the real benefit is having your aging parent comfortable, or overnight guests relaxing in style and comfort in your backyard instead of at a hotel down the street. Just imagine how much more enjoyment you will get out of your backyard when there is a small and stylish home there.

If you are considering designing and building an ADU in Los Angeles for any reason, please give us a call or drop us a line to schedule a Free ADU Consultation. We are more than happy to share our knowledge of ADUs and can help you understand what is possible in your backyard.

Good luck and let me know if I can help guide you on your ADU journey.

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