The definition of tiny but mighty, Accessory Dwelling Units (ADUs) have paved a path for themselves in the world of home renovations, design and architecture. Lili Weigert is one such ADU enthusiast and now author of Making Space: ADUs for Modern Living, which debuted on October 28, 2025.
ADUs are exactly what they sound like — a secondary housing unit that provides extra space for the homeowner. While the homeowner can determine how the unit is used, by definition an ADU must include a kitchen, bathroom and separate entrance. In Making Space, Weigert explores both the practicality and beauty of some exemplary ADU designs, with a bounty of images to complement her writing.
We sat down with Weigert to learn more about her personal ties to the world of ADUs and what sparked the idea to write Making Space. Keep reading to see what she had to say, and get a deeper glimpse into what her book features here.
What inspired your interest in ADUs?
I used to live in something similar to an ADU, but it was called an earthquake cottage. Hundreds of these were built as temporary housing after the 1906 San Francisco earthquake, intended to shelter people while their homes were rebuilt. They were all supposed to be demolished but a few survived, especially in certain neighborhoods like Bernal Heights and Noe Valley, where I lived.
My house was only 630 square feet. It had two bedrooms when I moved in, but I knocked down some walls to create a more open living and kitchen area. Tucked behind a three-story Edwardian, the cottage was invisible from the street and accessed via a side path, with its own private brick patio. That cottage was the beginning of my interest in small-space living. I learned firsthand that 630 square feet was plenty of space for one person and that, in many ways, living smaller was easier.
When did ADUs start becoming more common?
The first time I heard the term was in 2021, when a friend bought a house near me in Marin County. His property had a large, flat backyard, and he mentioned new legislation that might allow him to build a second unit there. Given California’s housing crisis, it made sense that the county would encourage homeowners with extra space to help expand the housing supply.
After that, I started hearing about ADUs everywhere. Building sites listed “ADU construction” among their services, architecture firms began calling themselves “ADU specialists,” and builders started incorporating ADUs into new home designs — sometimes instead of a garage.
Why now? Why should people consider ADUs for their own homes?
ADUs aren’t just easing housing shortages, they also offer environmental benefits, strengthen community connections and add significant property value.
In recent years, events like the pandemic and extreme weather driven by the climate crisis have forced us to adapt quickly, rethinking how and where we live. While “home” used to mean stability and continuity, what many of us need most today is flexibility — space that can evolve with changing circumstances. An ADU provides exactly that, whether it’s for multigenerational living, a home office, rental income or simply room to adapt as life changes.
Does building a small structure mean homeowners have to sacrifice design?
I think in some ways it’s the opposite. Designing within a smaller footprint just means you have to be especially conscious of the best use of the space for your particular needs. It’s an opportunity to bring your personal design style to life in a more manageable and modern way.
What inspired you to write Making Space?
I’m excited about the proliferation of ADUs and urban infill architecture as solutions to the global housing crisis. I’m also excited for people to see how fabulous and design forward ADUs can be.
Back in 2023, I went on an organized ADU tour in Los Angeles. While inside the most beautiful ADU I’d ever seen, gorgeously and painstakingly designed from the ground up by local architecture firm Bunch Design, I kept overhearing people saying, “This is an ADU?” or “I didn’t know an ADU could be this nice.” I suppose because of their smaller size and relationship to the main house, people assume ADUs won’t have architectural beauty or sophisticated design.
What are some different uses for ADUs?
The beauty of the ADU is its flexibility. I’ve seen an ADU used as an art studio, a classroom and a space to practice the Feldenkrais method.
Can you provide an example from the book for how an ADU solved a homeowner’s needs?
The Jewel Box, in Seattle, was designed for a homeowner after he retired. He wanted the flexibility to travel so he rented out the main house and built the 500 square feet ADU to use as his home base.
How can homeowners keep costs down when building an ADU?
In my book, Meredith Munger, my ADU-financing expert, talks about how to “value engineer” an ADU project. “There are many ways to bring costs down without impacting the beauty and luxury of the ADU,” she says. (She has some great recommendations, but you’ll have to read the book!)
