Permit Required? Required
Typical Fee Range $10,000–$22,000 Total permit costs include building, electrical, plumbing, and mechanical review.
Fee Method Project-based
Apply Online Apply at Inspectional Services Department →

What's Required in Boston

  • Homeowner must reside in the 1-, 2-, or 3-family home on-site.
  • Full architectural and structural plans stamped by a MA engineer.
  • ADU must contain independent cooking, sleeping, and bathroom facilities.
  • Must meet all MA State Building Code (780 CMR) standards.
  • Zoning Board of Appeal (ZBA) review may be required for detached units.
  • Utility separation or shared capacity must be professionally verified.

How to Get a ADU Permit in Boston

1

Step 1: Check Eligibility

Confirm property is a 1-3 family home and you are the resident owner.

2

Step 2: Design Phase

Hire an architect to create plans meeting ADU Guidebook specs.

3

Step 3: Portal Submission

Upload all structural and trade drawings to Boston ISD online.

4

Step 4: ZBA Review

Attend a hearing if a zoning variance is required for your lot.

5

Step 5: Multi-Stage Inspections

Full series from foundation and framing to final occupancy.

Frequently Asked Questions

Yes, internal conversions of basements or attics are allowed in Boston.
Yes, ADUs typically cannot exceed 35% of the main house or 450-600 sq ft.
The permitting and construction process averages 4-10 months.