Medford, MA Accessory Structures: ADU Rules (2026)
ADU rules in Medford, MA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- ADUs per lot
- One maximum
- Size cap
- 900 sq ft or half the main house
- In-house ADU
- Allowed by right
- Detached ADU
- Needs Community Development Board permit
- Permit term
- 5 years, renewable by affidavit
- Exterior change limit
- Max 10% gross floor area increase
Summary
Medford lets homeowners add one accessory dwelling unit per lot under Section 94-8.2 of the Revised Ordinances: by right inside the existing house, or by special permit from the Community Development Board in a detached structure. The unit is capped at half the principal dwelling's floor area or 900 square feet, whichever is smaller.
94-8.2.2 Procedures. Accessory dwelling units may be allowed as of right in an existing principal dwelling or by special permit from the community development board (the SPGA) in an existing detached structure on the same lot, provided that each of the following additional conditions are met. ... 3.Not more than one accessory dwelling unit may be established on a lot.4.The accessory dwelling unit shall not be larger in floor area than one-half the floor area of the principal dwelling, or 900 square feet, whichever is smaller. Exceptions may be made by the SPGA in the event that the detached accessory structure has some preservation value, as with a carriage house or a barn.
Full Breakdown
Section 94-8.2 of Chapter 94 authorizes accessory dwelling units (ADUs) in the City of Medford to give owners of oversized single-family homes a way to share housing costs and provide options for elders and small families. Section 94-8.2.2 allows an ADU "as of right" when it is built inside the existing principal dwelling, but a detached ADU in a separate structure on the same lot needs a special permit from the Community Development Board, acting as the special permit granting authority. Section 94-8.2.3 sets the operating conditions: no more than one ADU per lot, a plot plan showing the unit, septic system and parking, and a size cap of one-half the principal dwelling's floor area or 900 square feet, whichever is smaller, though the Community Development Board can grant exceptions for a detached structure with preservation value such as a carriage house or barn.
The exterior of the building holding the ADU cannot be "significantly altered," defined as no more than a ten percent increase in gross floor area and no new entrance facing the street. Owners must provide at least one on-site parking space for the ADU when feasible, using permeable paving if newly built. A detached-structure special permit expires after five years but the building commissioner can renew it every five years without a new public hearing if the owner files a renewal affidavit.
Violations & Fines
Building or occupying a detached ADU without the required special permit, or exceeding the one-unit-per-lot and size limits of Section 94-8.2.3, is a zoning violation the building commissioner can enforce through a stop-work or cease-and-desist order. A special permit lapses if it is not renewed with the required affidavit every five years.
Frequently Asked Questions
Can I build a detached ADU in Medford without a permit?
How big can a Medford ADU be?
Does a Medford ADU special permit expire?
Sources & Official References
Other rules in Medford
How Medford compares: Easiest Cities to Build an ADU·Compare Medford to another location·View the Massachusetts accessory structures overview
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