I'm a single mom living with other single moms. One simple design transformed our floor plan and gave us privacy and storage.

• I bought an apartment building with another single mom to help us build equity and share costs.
• The longtime rental needed renovation, and one simple design change made a world of difference.

When I decided to purchase a house with another single mom, we had a set of criteria that limited our options in the hot Washington, DC, housing market.

We wanted a multifamily property that would allow two units of similar size. We were prepared to retrofit, do some updates, and make some compromises.

When we found our perfect four-unit apartment building, my unit needed a kitchen update, but I was prepared to live with the awkward layout to save money. My coinvestor, who has two kids — 10 and 13 — and needed three proper bedrooms, was not.

The 1927 floor plan technically had three bedrooms, but it was hard to make sense of how privacy and storage were going to meet her needs. So we called in an expert to help us take our dream to the next level.

I hired an architect friend with a passion for cohousing to work up plans

If someone told me I would someday spend $40,000 on a hallway, I would laugh, but that's what we did.

"Holly's design had everything I enjoy," said Ileana Schinder, an architect, a mom, and the author of "Housing for Humans: A Book to Imagine, Create, and Design a New Housing Model in America." I hired Schinder as the architect to help us reimagine the floor plan.

Each apartment needed more privacy for each bedroom, a more effective kitchen, and an economic use of space. Schinder used the existing closet to create a new circulation path between the front and rear. An existing closet was transformed into a hallway to redistribute circulation and support these uses: bathroom, privacy, and entry storage.

Schinder has experience working with small spaces, her specialty is additional dwelling units, or ADUs, where basements and garages are transformed into small homes in urban settings. She's committed to projects like Siren House, what we call our cohousing place, and advocates a new housing model in the US that addresses compact and modern housing issues from an urban and social perspective.

Saving up to grow means we have a lot to consider

Our property has four units. The attic studio is rented, and the basement two-bedroom is now owned by another single mom of two who "bought in," as we offered her a rent-to-own option.

As the children grow up, more space downstairs and for group activities may be required. We're looking at long-term expansion.

"Alterations to the existing building should consider the group needs," Schinder said. "Options range from private spaces added to each unit in the shape of a rear addition to more public shareable spaces, like an outdoor-indoor cabana that can host birthday parties, work, and large gatherings throughout the year in DC, from hot August BBQs to a winter gathering around a firepit."

Projects in cohousing buildings must balance the individual needs of each family as it grows, and the group benefits from shared activities to avoid underused — and expensive — spaces. One option we've considered is our own ADU.

"An additional dwelling unit in the rear can also bring in extra income to support the finances of the group, this structure should maintain privacy and security for all residents," Schinder said.

If we could design from scratch, we would absolutely call in our expert

While our imaginations jump to art studios and rooftop gardens, a good architect will remind us of how to design and make a smart, sustainable investment in the structure's value and use.

"It's important to balance private and public uses when designing any home," Schinder said. "We want to bring in the benefits of shared activities while maintaining long-term market values of the property. An empty lot can be the canvas to have multiple structures of different sizes or grouped together in one building."

Our family, our timeline, and our budget are all conditions for our project, and those same considerations go into a from-scratch build. Plus, you need to factor in the location available for the project.

Right now, we have more dreams than dollars, but we're going to be consulting with Schinder every step of the way.

Holly Harper is the founder of Anagram Consulting, Blue Bike Communications, and Siren Foundry. She and the founders of Siren House are also the cofounders of Main Street Pearl.