Whether you’re looking to expand the amount of livable space on your property or you would like to add a source for potential rental income, building a prefab ADU in Portland can be a wise decision. While there may not be the same number of ADU builders in Portland as there are in cities like San Francisco or Los Angeles, buyers still benefit from a few local companies and builders based in the Pacific Northwest that can still help with your project,

To help individuals as they consider their builder options for an ADU in Portland, we have created a list of some of the leading builders and their most popular floor plans. The Portland ADU builders that we have included have been chosen due to their unique product offerings and operating history as prefab home and ADU builders. Similarly, the ADUs featured on our list have been chosen for their size, unique aesthetics, and availability in portland.

Best Prefab ADUs in Portland

Oregon-Based ADU Builders

Haven by ideabox - Salem, OR

The Haven is ideabox’s smallest models and is well-suited for use as an ADU in Portland. At 781 square feet in size, it features one bedroom, one bathroom, and an open living area. It has large, sliding glass doors, and a sloping shed-style roof. Our turn-key estimate for a Haven ADU is $390,000.

As a company, Ideabox offers a series of both standard and custom homes, which buyers can either choose from their line of less-expensive manufactured homes, or slightly more expensive modular homes. It is also worth noting that ideabox does not complete on-site construction. Therefore, buyers must work with a local contractor for site preparation and finishing the modules. Ideabox estimates that local work makes up around 40% of the total project budget. Our turn-Key cost estimate for an ADU or prefab home from ideabox ranges from $400 - $500 per square foot. For more info, see our list of ideabox ADUs with cost info.

While they are not currently accepting new projects, Dweller is a Portland ADU builder that may be a helpful resource for your project.

Out-of-State ADU Builders that Sell Prefab ADUs in Portland

TimberCab 621 by FabCab - Seattle, WA

The TimberCab 621 is the smallest of FabCab’s timber-inspired home series. It has an open living area, one bedroom, and one bathroom. FabCab notes, however, that this floor plan should be used for inspiration in designing a semi-custom ADU. It has a shed-style roof, large windows, and interior wooden accents. We estimate a completed 621 to cost around $220,000.

FabCab designs and manufactures two series of ADUs and smaller homes that feature either modern or timber-based aesthetics. Their panelized homes range in size from smaller, 550 square foot ADUs to 1,400+ square feet homes. Our turn-Key cost estimate for an ADU or prefab home from FabCab ranges from $448 - $611 per square foot. For more info, see our list of FabCab ADUs with cost info

Passive Prefab ADU by Artisans Group - Olympia, WA

The Passive Prefab ADU is one of several custom ADU designs by Artisans Group architecture. It features both modern and traditional architectural influences and makes heavy use of both glass and wood accents. The Passive Prefab ADU is part of their custom design portfolio and can be purchased as either an 800 or 1,000 square foot ADU. Our estimate for a completed Passive Prefab ADU is around $400,000 with a $15,000 design fee.

Artisans Group is an architecture firm that designs environmentally friendly homes built to passive house design standards. They primarily focus on prefab construction and specialize in modern architecture and unique elements. While they are able to work with clients across the U.S. their primary focus is on projects in the Pacific Northwest. Our turn-Key cost estimate for an ADU or prefab home from Artisans Group ranges from $400 - $600 per square foot. For more info, see our list of Artisans Group ADUs and homes with cost info

Summit Semi-Custom ADU by Studio Shed - Louisville, CO

The Summit Series by Studio Shed is a line of semi-custom ADUs and home studios. Buyers can choose from a range of ADU dimensions and sizes which range from 256 - 1,000 square feet. Additionally, buyers can modify elements such as kitchen & bathroom placement, windows & doors, and all finishes. To get the most accurate price for your ADU, buyers can customize their own model using Studio Shed’s interactive tool.

Studio Shed specializes in the design and manufacturing of studio, ADU, and smaller home kits.. While they can not build fully custom designs, they offer a high degree of flexibility such as floor plan arrangement, window and door placement, and home finishes. Their homes are shipped as building component packages that must be assembled on site. Our turn-Key cost estimate for an ADU or prefab home from Studio Shed ranges from $360 - $570 per square foot. For more info, see our list of Studio Shed ADUs with cost info 

ADU Builders in Portland

While it can be helpful to choose between Portland ADU builders based on their prefab design offerings, it may also be useful to compare builders side-by-side. That way, you can evaluate companies by comparing attributes such as location, cost, services offered, and whether or not they offer custom design services. That way, you can truly determine which ADU builder in Portland is best suited for your situation.

As we’ve noted above, prefab ADU construction allows buyers to work with companies that are not necessarily located in the same city as the project. That is because a manufacturer can work on the home off-site, and a separate builder can complete the local parts of the project. In the event that you would like to work with a builder that is located outside of Portland, it is important to remember that there will likely be added shipping costs. Depending on the construction type (modular vs. panelized vs. kit), shipping can sometimes be as high as $15 per square foot.

In addition to ADUs in Portland, other resources that you may be interested in include:

• Guide to Building a Prefab Home in Portland

• Tiny Homes for Sale in Oregon

• Interview with Kol Peterson on the ADU Building Process