Renowned Custom ADU Builders in Portland, OR

The cost of a freestanding ADU in Oregon can vary widely based on size, design, site conditions, and finishes. Our builders work with you early in the planning process to align your goals with a realistic budget. 

Whether your project is part of a larger outdoor living transformation or a stand-alone undertaking, our new build contractors ensure everything is thoughtfully integrated into your property. This helps avoid unexpected costs by keeping everything transparent and coordinated from the start. 

You will never be left guessing where your money is going. You get a complete, high-quality build with no surprises and a final result that reflects your vision, just like we’ve done for many home remodeling clients in Beaverton and other nearby areas.

Oregon sets statewide standards that accessory dwelling unit builders in Portland need to follow, while the city adds its own local rules. In Portland, you’ll need a building permit, and the project also has to meet requirements related to size, placement, height, and the conditions on your property.

We review those details during feasibility so you know what your property can support before the design gets too far along. That gives you a realistic starting point without having to sort through state and local requirements on your own.

In Portland, the placement of a detached accessory dwelling unit relative to your primary residence and property lines is governed by specific zoning regulations. Typical requirements include:

• Side and rear setbacks: Generally at least 5 feet from the property lines
• Front placement: At least 40 feet from the front lot line or behind the rear wall of the primary home

This is nothing to worry about since your ADU contractors will handle all aspects of zoning analysis and site planning for you, just like for any home remodeling project.

Our process typically includes 6-8 weeks for feasibility, 8-12 weeks for pre-construction, and 4-9+ months for ADU construction in Portland. That puts many projects at roughly 7-14+ months from the first feasibility work through completion.

The exact timeline depends on the scope, site conditions, permitting, utility work, and other project-specific factors. Still, working with our experienced custom ADU builders can help ensure a smoother, more efficient process, while managing expectations for any potential delays.

Your ADU contractor will likely explain that in most Oregon cities, a detached accessory dwelling unit can be up to 800 square feet, though some areas allow more depending on your lot size and local code. The city recently lifted certain restrictions, which can open up larger build options if your site qualifies. 

Your custom ADU builders in Portland will take these variables into account when designing your space and will walk you through what’s allowed on your property. Our goal is to get you the most usable space possible while staying compliant. You’ll get a custom addition that maximizes both square footage and long-term value.

Not always. Some utilities can be shared with the main house, while others may need separate connections depending on the design and existing systems. This can be especially important with a detached ADU, where water, sewer, and electrical service may need to extend farther across the property.

We plan for those details early so the utility setup is clear before construction begins.

In some cases, yes. Portland allows two accessory dwellings on certain qualifying properties, although the exact setup depends on the site and zoning. You may be able to pair an internal or attached ADU with a separate unit, or build two detached dwellings where the property allows it.

The right arrangement depends on what your lot can support and how you want to use the space.

Yes. A separate dwelling can make an ideal guest house, giving visiting family or friends their own kitchen, bathroom, living area, and entrance without putting everyone under the same roof.

It can also serve a different purpose later, such as housing a relative or becoming a long-term rental, so it helps to think beyond just the way you plan to use it today.

Definitely! In fact, partnering with reputable custom ADU construction services is an excellent way to generate rental income. Many homeowners build ADUs specifically for renting out to tenants, providing a private living space with its own entrance and amenities. This additional space can be rented on a long-term basis or even as a short-term rental, depending on local laws. 

High-quality ADU construction can create a steady stream of rental income that can help offset housing costs and add long-term value to your property.

COOPER Design Build is Portland’s trusted ADU construction company, providing quality, custom home renovations, which include beautifully constructed freestanding ADUs. With decades of experience and a fully integrated team of designers and builders, we handle everything from design and permitting to construction and finishing details. 

We take on a wide range of projects, including thoughtfully planned condominium renovations, and serve clients throughout the region, from Portland to high-end home remodeling in Lake Oswego, and much more. Whether you’re tucked near Forest Park or overlooking the Willamette River, we bring thoughtful design and lasting value to every square foot. 

Schedule your consultation today with our award-winning experts in ADU construction and take the first step toward building something exceptional!