Owner-Builder ADU by Kat and Dad

Quick Facts

Setting: suburban

Neighborhood: Buena Vista, Walnut Creek, CA

Type: detached

Use: rental

Square Footage: 1,200

Year Built: 2020

Owners: Kat and family

Designer: self

Builder: self

Total Cost: $200,000

When we saw this fixer-upper on a half-acre plot of land, I knew right there and then: we were going to buy it. That was back in 2018, and my father started plotting the renovation strategy while exploring the property. One of its best features was the enormous unoccupied front yard, which seemed like a good spot for a second house. We were about to discover the secret world of ADUs and embark on an exciting journey of building one.

Planning

First pleasant surprise were the changes to California housing legislation in 2017, making it easier to build ADUs. Second, I learned that our new property belonged to an unincorporated subdivision of Contra Costa County, allowing the maximum ADU size in the state: 1,200 sq ft (unlike the City of Walnut Creek with 800 sq ft). Then came another piece of good news: there was enough space in the front yard to observe the zoning ordinance and setbacks. It was my mother’s idea to build specifically in the front yard to utilize the unused hilly area and provide easy access to ADU by the tenants, while keeping the privacy of our backyard. The hill complicated the design and build process, but I believe it will ultimately pay off.

After getting the ADU packet from the building department, I started gathering the required documents. We considered all kinds of designs: from prefab and panelized kits to steel and wood framing. Eventually, we landed on the traditional stick frame for its price and ease of build: the infamous hill did not allow for any standard designs so we had to build custom. Having found remotely similar plans online, we took them to a design firm to turn our ADU concept into architectural and structural plans. They listened attentively and delivered exactly what we had in mind: split-level, 3 bedroom, 2 bath unit with a large family room and an open-space kitchen. The mock designs helped us visualize exactly what we’re building, minus the exterior finishes that needed to match the existing house in white and blue:

Here are the floor plans in PDF and AutoCad formats for anyone interested.

Permitting

With all the documents in hand, I filed a permit application in November 2018. Because of my travels afterwards, it took longer than usual to get approved, but after 7 months of back and forths I got a shiny new permit in June 2019. It wasn’t cheap – $16.5k – but I knew we’d reap significant savings when building ourselves. Applying as owner-builders taught us everything we needed to know from properly reading the plans to successfully passing inspections. Besides, the building department was beyond helpful and understanding: they told me exactly what the structural engineer was missing, how we should approach the building process, and where to find help. I had the building code hotline on speed dial and got to know many of the employees by name. Any myths that the building office is there to make my life difficult were shattered: quite the opposite, it was there to help.

Some of not so exciting surprises came from the public utility agencies: my water and sewer connections ended up costing a fortune. $36k was the price tag for a separate water meter required for ADU and $5k was the sewer lateral connection. Overall, permits added up to $60k or 30% of my total budget.

Building

With the permit in hand, all the building fun began. My father never built from the ground up in California, but he’s had a lot of experience in Ukraine. The two parts of the job he was absolutely uncomfortable with were foundation and electrical, so I started looking for subcontractors. Everything else was taken care of by him and yours truly: we broke the ground, did our own excavation and compaction, and waited for the foundation to be approved before we could start framing. That part didn’t begin until March 2020, due to some foundation design changes and abnormally rainy winter. When COVID-19 pandemic hit, we were grateful for construction stores to remain open and completed the bulk of the work during the 3 months of shelter in place. Framing was my favorite part: it was fascinating to see the structure take shape, piece by piece. We did most of the things very old school: my father didn’t let me buy a nail guy and ended up doing it all by hammer. We also opted for roof rafters instead of trusses, which helped to keep the budget down. A key factor during this phase was working with an experienced framing consultant that I found through Craigslist: without doing any physical work, hwe would come out on site to confirm we were doing things right.

My part in the process was mostly in ordering materials, coordinating inspections, and figuring out the budget. For the materials, we simplified things by ordering from 2 stores only: local lumber yard for framing and hardware, and Home Depot for everything else, from insulation and doors to lamps and kitchen appliances. I also took care of subcontracting foundation and electrical work, which seemed like a Herculean effort: finding professionals who were available and charged reasonable prices took quite a while. I am still puzzled by the fact that my foundation quotes ranged from $18k to $140k, and electrical – $3.5k to $24k. With 95% of the project complete, we’ve spent close to $200k so far:

The detailed budget breakdown is available in this spreadsheet.

After learning the ropes in the process, I could not keep all the information in my head and needed to share. This inspired me to start a series of blog posts about my ADU journey, which was later accompanied by analytics on the state of ADU in California. The purpose of the entire blog is to inspire fellow homeowners to build more ADUs, no matter if it’s 100% DIY or completely turnkey. Whatever your purpose is – to earn rental income, have grown up children live nearby, or retire in place – ADUs can be a perfect solution for that. Besides, they are meant to address the housing affordability all over the country, and I’m looking forward to the day we can put the term “housing crisis” to rest.

Please reach out with any questions, comments, ideas – happy to share all I know about ADUs to date. I also promise to post a video walkthrough of the unit once it’s finaled and ready for prime time!

~ Kat