ADU and DADU Construction Services in the Greater Seattle Area
Haas Development & Construction provides accessory dwelling unit (ADU) building services throughout the Greater Seattle area. They work with homeowners to design and construct both attached ADUs (AADUs) and detached ADUs (DADUs), tailoring each project to the specific characteristics of the property and the goals of the homeowner.
The City of Seattle permits most homeowners to build up to two ADUs on the same residential lot. Depending on the size and layout of a property, homeowners can combine different ADU types:
- Both units can be attached or internal to the existing living space (AADUs)
- One attached ADU (AADU) combined with one detached ADU (DADU)
An accessory dwelling unit can serve multiple purposes — from housing extended family members to generating rental income. Beyond the financial benefits, an ADU can offer greater flexibility in how a household uses its property over time.
What Haas Development & Construction Offers
As an experienced ADU contractor in Seattle, Haas Development & Construction handles projects from the earliest planning stages through to move-in day. Their process is structured to guide homeowners through each phase:
- Getting Started — Assessing whether the property can accommodate an ADU or DADU
- Planning — Working through the details of the project scope and design
- Custom ADU Solutions — Selecting a design package and customizing it to suit individual needs
- The Build — Constructing the unit to the desired level of finish and completion
- Move-in Ready — Delivering a completed, livable space
For custom ADU and DADU builds, their team provides planning and permitting assistance, expert design and engineering, and fully custom construction. They also offer pre-approved prefab DADU plans for homeowners looking for a more streamlined path to building a detached accessory dwelling unit.
Certified DADU Specialists
Haas Development & Construction positions itself as a certified DADU specialist in the Seattle market. Once a DADU plan, property configuration, and permitting details are confirmed, their team of contractors and engineers manages the full scope of construction. This includes:
- Excavation and demolition
- Concrete and framing
- Electrical, plumbing, and mechanical engineering and implementation
- Final finishes
Whether a homeowner is considering a backyard cottage, a detached granny flat, or an attached in-law suite, Haas Development & Construction offers the experience and structure to manage the process from start to finish. Their team is available to advise on new projects as well as those already underway.
