How to build an ADU from the ground up… even if you have zero construction experience.

Accessory Dwelling Unit (ADU) Developments Can Be Very Profitable!

Taking a piece of real estate and improving it by adding an ADU is a relatively easy form of Real Estate Development that even a novice real estate investor or homeowner can accomplish with the right guidance.

Over the course of the next 12-16 weeks I will take you along as I build a brand new 1,200 sqft ADU on a property in Hyde Park, Los Angeles. I will be sharing a step-by-step "how to" which covers the entire ADU construction process from the initial design to final inspection.

Farmhouse ADU Being Developed in Los Angeles, California

This ADU is being constructed on a property I own, and I am acting as my own General Contractor. Although I am a licensed General Contractor, the information I provide in this guide will benefit anyone who is ready to start building their own ADU, even if you have little or no experience in construction. If you have a willingness to learn and are not afraid of a little hard work, then you can build your own ADU which you can use for investment or personal enjoyment. Or both.

If you have any questions or would like to discuss your own ADU construction project, please do not hesitate to call or email me with questions or comments. I look forward to sharing this process with my community and I encourage all homeowners and investor who can add an ADU to their property in Los Angeles to do so. Our great community needs more housing and we can help by providing additional housing options for our fellow Angelenos.

Step #1 - Choosing the type of ADU that is best for you. Attached vs Detached vs Garage Conversion.

For me, I wanted to maximize my return on investment, so I chose to design and build the largest ADU that was allowed. Every square foot you build equals a higher rent you can command and a higher eventual sales price when it is time to sell. I wanted a 3bd/2ba ADU that I could rent for top dollar. I chose to build a detached unit because I had room in my backyard, and I thought that a detached ADU would be more desirable for a family looking for a home. And as any real estate investors knows, families tend to stay longer which equals less tenant turnover which equals less headaches.

Once I settled on the type and size of ADU I wanted to build the next step was to get a design in place and construction drawings produced.

I knew exactly what I wanted and since the ADU was only two stores I didn't need a licensed Architect to come up with a new ADU design, I simply hired an experience draftsman to prepare the plans, and Structural Engineer to provide structural calculations. It is particularly important that you hire a draftsmans or architect that is experienced in designing ADUs, and experienced working with the city you live in. DO NOT try to save a few dollars by hiring someone that does not have experience with ADUs, or an Architect or designer that does not work full-time in your city. An inexperienced designer, Architect, or Engineer can add months to your project timeline if they are not familiar with the ADU ordinance and how each city treats the permitting process.

Once the designer is done with your plans the next step is to submit the plans to the city and wait for their comments or approval. In my case it took the City of Los Angeles about 30 days to review my plans, and after I made a few minor corrections to the plans based on the cities feedback, I had permits in hand and was ready to start construction.

Step #2 - Building Your New Accessory Dwelling Unit

  1. Site Clearing & Building Pad Preparation

    The main house on my property was built it 1914 and was an old craftsman style bungalow. At the time it was built it apparently had a two-car detached garage space, but at some point over the last 100 years the garage had been destroyed. I am not sure what happened to the original garage, but it wasn't standing when I bought the property in the Summer of 2019. The only evidence that a garage once existed was contained in old building permits from 1914 that showed the size and location of the original construction. It was the existence of these old building permits that lead to the first delay in the construction of my new ADU. Since the building departments records showed the existence of a garage on the property, I was required to pull a demo permit to remove the garage. A garage that no longer existed on the property. And to top it all off, the City of Los Angeles required that I send all my neighbors within 500 feet a notice notifying them that I was going to demolish the garage and give them 30 days to voice any concerns regarding the demo to the city. Haha. Classic! So, I paid for my demo permit, sent the neighbors a "notice of pending demolition" and waited for 30 days to start my project. A complete waste of time and money since I had to pay 30 days worth of mortgage expenses and taxes waiting for a demo permit for a garage that had long ago been demo'd. Oh well.

    I finally had the permits complete and was ready to start building my foundation. My backyard is almost completely flat, so my engineer designed a slab-on-grade foundation for my ADU. This is the least expensive foundation to build and is perfect for an ADU foundation on a flat property. But slab-on-grade foundations require a flat surface to build on and so I went to work clearing out all the trees and vegetation that was in the footprint of my new ADU. You will see from the picture below that there was one old tree that was the biggest obstacle. A few quick calls to tree trimmers on Craigslist and I found a company that would remove and haul away the tree for $1,100. That was a bargain and I quickly scheduled the tree removal.

    Removing a large tree in the footprint of the ADU foundation.

  2. Foundation Footings

    The engineer designed a 6" thick slab with 18" wide and 18" deep footings. Since the dirt was relatively soft and the foundation area relatively small, I proceeded to hand dig the footings as the cost of renting equipment would have doubled the overall cost of digging the footings. I used two hard working construction laborers to help, and with my guidance I was able to dig the entire foundation and prepare the footings in a little under 16 hours of work. Now that we have the footings dug it is time for the next step… underground utilities.

  3. Underground Utilities

    At this point in the build it is necessary to run any underground utilities that will run underneath the foundation slab. For this build I have chosen to run the property entirely on electric power. I chose to use electric only to save a little money on the build. Running only electric to the ADU meant I did not need to run gas lines which saved about $3,500. This decision means that the only underground utilities I have running under the foundation slab and through the footings was my plumbing waste lines.

    The picture below shows the underground plumbing lines installed under the slab. At this point we called the city inspector to come out and approve the foundation pad and footings, and to perform a water test and approve the underground plumbing. With the inspectors blessing we back filled the sewer trenches and started progress on preparing the slab for our concrete.

    Foundation Footings and Forms For Our New ADU in Los Angeles

  4. Adding Structural Rebar

    After the underground plumbing was complete and the plumbing lines backfilled with soil and compacted, it is now time to place the rebar to our footings as designed by our Structural Engineer. The rebar is structural steel that is placed inside the concrete footings and provides the concrete with added strength. In addition to rebar in the footings, the engineer also called for the slab to be reinforced with wire mesh, as well as a vapor barrier over the soil which would prevent moisture from the ground soaking into the slab from the bottom.

    The picture below shows what the foundation looks like just before we placed the concrete.

    Slab on grade preparations for an ADU in Los Angeles
  5. Placing the Concrete

    After we placed the rebar into our footings, the with vapor barrier and wire mesh across the slab area it was time to pour our concrete. We called the city inspector out to the job site to approve the rebar, vapor barrier, and wire mesh. The inspector gave us his blessing and told us to call him back out after we were done with the rough framing portion of the project.

    A quick note on inspections... never cover up any work until that work is seen and approved by a city inspector. So, in this case when we pour our concrete we are going to cover up the rebar, vapor barrier, and wire mesh work we performed, so it was necessary to call out the inspector before that work was covered. Once the concrete is placed into the ground the work gets covered up and there is no way for the inspector to verify we performed the work to code or the approved structural design. Always, always, always call the inspector before you cover up you work. You will see as we progress on the project that the inspector is always called out right before we cover work.

    Back to pouring the concrete. The engineer called for a standard 2,500 PSI concrete and our calculations showed that we needed about 27 yards of concrete to complete the slab. We hired a skilled set of concrete finishers to place and finish the concrete. A crew of four men were able to get the concrete poured and finished in about 4 hours.

    The picture below shows a progress picture of the concrete being placed into the footings and slab.

    Slab on grade in progress for an ADU in Los Angeles

Next Week's Blog...

Next week we will have pictures of the completed foundation and will begin the rough framing portion of our ADU project. We'll see you in a week or so with an update.

If you're thinking of building an ADU anywhere in the Los Angeles contact us. We're helping homeowners just like you all over Los Angeles build ADUs and Granny Flats.