ADU vs DADU: What’s the Difference
— and Which One is Right for You?
In Seattle, more and more homeowners are putting their unused space to good use by building an ADU or DADU.
This isn’t just a trend — it’s a smart way to increase your property value, generate rental income, or create private space for family.

But what exactly are ADUs and DADUs — and how do they differ?

What is an ADU?


An ADU (Accessory Dwelling Unit) is a secondary living space attached to your main home.
It can serve as:
  • A private apartment for family
  • A rental unit
  • A home office or creative studio
Types of ADUs:
  • Attached ADU— an addition connected to the main home (e.g. over a garage or side extension)
  • Basement ADU— a converted basement
  • Garage Conversion— a remodeled attached garage


What is a DADU?


A DADU (Detached Accessory Dwelling Unit) is a completely separate structure built on the same lot as your main home.

It’s often called a“backyard cottage,” “lane house,” or “tiny home.”

A DADU is a fully independent residence — with its own entrance, kitchen, bathroom, and utilities.


At Modern Buildings, DADUs are our specialty.

Why Are So Many Homeowners Choosing DADUs?
In Seattle and surrounding areas where land is expensive, building a DADU means creating a second home without buying a new lot.
You can:
  • Rent it out
  • Use it as a guesthouse
  • A separate space for aging parents
  • Sell the DADU and keep your current home
Need Help Getting Started?
At Modern Buildings, we specialize in full-service of ADU and DADU construction in Seattle and the greater King County area.
We handle everything: feasibility assessement, architectural plans, permits, construction, utility hookups, everything through final inspection.
Contact us for a free consultation — we’ll evaluate your lot, walk you through what’s possible, and answer all of your questions.
Get a free consultation