10 Common DADU Concerns of Homeowners

When considering building a DADU, Homeowners have multiple concerns, from Zoning to Size limitations, Utilities, and building green.

1. What homeowners need to know about Zoning and Eligibility

Among the 10 Common DADU concerns homeowners have about building a DADU is knowing if your property is eligible.

Most single-family and low-rise residential zones allow DADUs.
Lot size no longer has a minimum requirement, but setbacks and lot coverage rules still apply.
Your property must have an existing single-family or multi-family home.

2. Questions about Size & Height Limitations are Frequent Asked

Maximum floor area: 1,000 sq. ft. (including lofts).
Maximum height: 14–24 ft., depending on lot width.
Setbacks: Generally five ft. from side/rear lot lines and 10 ft. from alleys.

3. Parking Requirements for DADUs

No off-street parking is required for a DADU, but it may be helpful for renters.
Those must still be met if your property already has parking requirements for the main house.

4. Owner Occupancy Rules are more lenient than they used to be

Seattle removed the requirement for homeowners to live on-site so that you can rent both the main house and the DADU.

5. Permit & Approval Process is the initial step

You’ll need a building permit from the Seattle Department of Construction & Inspections (SDCI).
The process includes site plan review, environmental codes, and possible neighborhood consultation.

6. Utility Connections & Infrastructure are widespread concerns

You may need separate water, sewer, and electrical hookups, which can increase costs.
Stormwater drainage requirements must be met.
If renting, consider separate meters for utilities.

7. Construction Costs

Construction costs are amongst the most addressed in the 10Common Concerns Homeowners Have About Building a DADU.

Costs typically range from $250,000 to $400,000, depending on design, materials, and labor.
Prefab and modular options can sometimes reduce costs.
How to save on costs on your DADU

8. Rental & Income Potential

DADUs can be rented as long-term housing (no Airbnb restrictions unless the property is your primary residence).
Adding a DADU can increase property value and provide extra rental income.

9. Green Building & Incentives

Seattle encourages green building with potential rebates for sustainable design.
Consider solar panels, rainwater collection, or energy-efficient insulation.

10. HOA & Neighborhood Considerations