Want to Design Your Own ADU? This Prefab Company Gives You the Tools

Type Five lets clients choose everything from floor plans to finishes via its website configurator, and then manages the rest.

Text by
Published by

Welcome to Prefab Profiles, an ongoing series of interviews with people transforming how we build houses. From prefab tiny houses and modular cabin kits to entire homes ready to ship, their projects represent some of the best ideas in the industry. Do you know a prefab brand that should be on our radar? Get in touch!

Aleksis Bertoni and Tim Thimmaiah started building homes because they felt the two most common ways were falling short of modern expectations. Designing and constructing one residence at a time—essentially "reinventing the wheel" with each project—seemed archaic. Prefab construction was fast, but limited the ways a client could customize a home. But the duo saw a way to improve on the latter by developing new software.

They established Type Five in Northern California to build ADUs by using a system of design and construction they call "site-build modular." According to design director Ian Miley, on the front end, it lets clients fine tune their small spaces via the company’s website, where they can select everything from layouts, to finishes, to colorways. Then, a proprietary software inputs these choices to produce construction documents. Here, Type Five shares how its design process helped a family develop a backyard ADU.

A family in Northern California custom-designed this ADU with prefab builder Type Five.

Photo by Adam Rouse

Tell us about the most exciting project you’ve realized to date.

We built an ADU for clients who are the second generation to occupy the primary residence, which was passed down from their parents. The original home was a small farmhouse, but the family added an addition to it about a decade ago. When both parents began primarily working from home during the pandemic, and their two children got older, the family was suddenly facing a severe shortage of space. They considered selling the property and moving into a larger house, but decided to build a multipurpose ADU instead.

The new ADU functions as a work-from-home office, a guest home for in-laws, and as a kid’s room. Type Five’s system allowed for an expedited design and build process so the family could use it as soon as possible.

Nestled into a hillside at the base of Tilden Regional Park in Orinda, California, the L-shaped ADU balances a small footprint with functional interiors. The design maximizes views into the coastal oaks on the property and the more distant redwood-covered hills in both directions.

The clients opted for a standing seam metal roof, weatherboard cladding, and an L-shaped plan.

Photo by Adam Rouse

Stay up to Date on the Latest in Prefab Homes

From cozy cottages to large family houses, see how prefab continues to redefine the future of construction, building, and design.


What does your base model cost and what does that pricing include? 

Our studio units are around 300 square feet and cost $200,000. This includes design, engineering, permitting, all site work, all construction, and appliances. Our standard finish package includes Bosch appliances, white oak hardwood flooring, Grohe plumbing fixtures, a Toto wall-hung toilet, and Corian solid surface countertops and shower walls. Type Five designs and builds ADUs all the way up to 1,200 square feet, which are priced at around $500,000 for a move-in ready home.

The living area connects with a bedroom that’s positioned at one end of the floor plan.

Photo by Adam Rouse

Where are the prefabs currently available?

Most of our homes are being built in the San Francisco Bay Area, and are between 300 and 1,000 square feet. We also have larger projects in development throughout California and the Pacific Northwest. We have plans to expand our operations to other U.S. states that are currently advancing new legislation aimed at increasing housing affordability through densification measures.

A full bedroom sits on one end of this ADU, with a second bedroom on the opposite end, for privacy.

Photo by Adam Rouse

Is your design currently pre-permitted in any U.S. municipalities?

Type Five is exploring pre-permitting in various municipalities. Our clients’ design selections are run through software packages we have built to instantaneously produce a set of extremely consistent, high-quality construction documents. Local building departments that have reviewed dozens of our permit sets are beginning to fast-track them due to the consistency and quality assurance we’ve been able to provide.

Clients can customize their ADU’s window arrangement.

Photo by Adam Rouse

How long can a client expect the process to take after they put down a deposit?

The design of the product is immediate, as clients can directly customize their home independently on our online configurator without placing a deposit. Once the design has been finalized and a deposit has been placed, permit-ready construction documents are generated instantaneously. Permitting takes between four to eight weeks, and construction commences immediately after, taking between four to six months.

A kitchenette comes complete with a cooktop and oven. White oak wood flooring, which comes standard with units, is used throughout.

Photo by Adam Rouse

What aspects of an install do you manage?

Type Five is a licensed California architect and contractor. We manage the entire process, from design and permitting to site work and construction, and we offer transparent pricing and schedules to give clients all the information they need to feel confident and comfortable.

A walk-in shower makes it possible for this ADU to eventually serve as a home to age in place.

Photo by Adam Rouse

What aspects of the design can a client customize?

Type Five offers a system that allows clients to customize many aspects of their home, including the footprint, layout, door and window patterns, and finishes.

On our website, a customer starts by choosing the size of their ADU, from a studio up to a two-bedroom unit. Then they can select from several shapes: linear, L-shaped, double-wide, or even a two-story plan, based on their specific needs and site features. From here, the customer can select the location of bedrooms, bathrooms, the kitchen, and storage spaces through a user interface. Once the layout has been finalized, customers can then choose from interior finishes, appliance packages, door and window hardware, and other details.

The second bedroom, currently arranged as an office, sits on the other end of the ADU, with a large picture window at the center.

Photo by Adam Rouse

A Murphy bed turns it into a bedroom as needed.

Photo by Adam Rouse

More Prefab Profiles:

Tini Living Makes Tweakable Steel-Framed ADUs That Start at $38K

A Tiny Home, an Office, and a Sauna: MyCabin Sells Its Prefabs as a Pack or à la Carte



Prefab Homes