How much does a detached ADU cost?

It's the most expensive ADU type because you're building a structure from the ground up with its own foundation and utilities, but it also returns the most in rent and resale value. We quote per project after the feasibility review.

How big can a detached ADU be?

In most cases up to 900 square feet, though your specific zone and lot can affect the limit. We confirm it before design.

How long does it take to build?

Plan for several months from design through permitting to final finish. Land-use and permitting timelines with the county are a meaningful part of that, which is why we start them early.

Detached ADUs & Backyard Cottages in Clackamas County

Gencon designs and builds detached ADUs and backyard cottages across Clackamas County, standalone units for rental income or family, with permitting and land-use handled end to end.

Free estimate: 503-825-0123

A detached ADU is a standalone home in your backyard, the most private and highest-value type of accessory dwelling. Gencon designs and builds detached ADUs and backyard cottages across Clackamas County, permits and utilities included.

Why build detached

Full privacy for tenants or family: separate structure, entrance, and outdoor space
Typically the highest rental value and resale appeal of any ADU type
Flexible use over time: rental, home office, guest house, or downsizing option
No shared walls or noise with the main house

What a detached build involves

A detached ADU is a small house: new foundation, framing, roof, insulation, and its own kitchen, bath, and living space, with water, sewer, power, and often gas run from the main house or the street. In most cases the unit can be up to 900 square feet, and it must match the primary home's materials, roof shape, and window styles to meet the county's design-compatibility standards.

Siting and setbacks

Where the unit can sit is driven by setbacks, typically 5–10 ft from side lot lines and 15–25 ft front and rear, though hillside and corner lots vary. We factor in slope, mature trees, utility routing, and access before finalizing the footprint, which is exactly what our feasibility review is for.

Frequently asked questions

How much does a detached ADU cost?: It's the most expensive ADU type because you're building a structure from the ground up with its own foundation and utilities, but it also returns the most in rent and resale value. We quote per project after the feasibility review.
How big can a detached ADU be?: In most cases up to 900 square feet, though your specific zone and lot can affect the limit. We confirm it before design.
How long does it take to build?: Plan for several months from design through permitting to final finish. Land-use and permitting timelines with the county are a meaningful part of that, which is why we start them early.

Detached ADUs is part of Gencon's adu construction work across Clackamas County. Explore related services:

Garage ADU Conversions

Get started on your detached adus project

Get a free, no-pressure estimate from a family-owned team you can trust.

Call 503-825-0123