ADU Locator

1 Best ADU Builders in Sequim, Washington

Verified ADU contractors and builders in Sequim, WA

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Cornerstone Builders

Cornerstone has been a Sequim ADU (accessory dwelling unit) builder serving Washington State’s beautiful North Olympic Peninsula over 40 years. As a design-build firm we manage every step of the ADU design and build so you can enjoy the process start to finish.

(360) 504-4381
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Frequently Asked Questions — ADU Builders in Sequim

How much does it cost to hire an ADU builder in Sequim?

ADU construction costs in Sequim, Washington vary widely depending on size, type, and site conditions. Detached ADUs typically range from $150,000–$400,000+, while garage conversions and attached ADUs can be more affordable. Contact multiple builders in Sequim to get accurate quotes for your specific project.

How long does it take to build an ADU in Sequim?

In Sequim, the ADU construction timeline typically ranges from 6 to 18 months from permit application to move-in. Permitting alone can take 2–6 months depending on Washington local regulations. Prefab and modular ADUs often have faster timelines than site-built units.

Do I need a permit to build an ADU in Sequim?

Yes, a building permit is required for ADU construction in Sequim, Washington. Your ADU builder will typically handle the permit application as part of their service. Washington has adopted streamlined ADU permitting laws in recent years, which may reduce wait times.

What types of ADUs can be built in Sequim?

Common ADU types in Sequim include detached ADUs (backyard cottages), attached ADUs, garage conversions, basement conversions, and prefab/modular ADUs. The best type for your property depends on lot size, zoning, and budget. A local Sequim ADU builder can advise on what's allowed on your specific parcel.