ADU Rules in Cambridge, MA
Cambridge follows the Massachusetts state baseline with local regulations.
HIGH Confidence Data
MA
State Baseline: Affordable Homes Act
Up to 900 sq ft or 50% of principal dwelling (whichever is smaller). By-right approval statewide.
Zoning Districts
A-1 — Residence A-1
Single-family residential, low density
Default Zone
| Type | Approval | Max Size | Height | Parking | Owner Occ. |
|---|---|---|---|---|---|
| Detached ADU | By Right | 900 sq ft | 15 ft | None | No |
| Attached ADU | By Right | 900 sq ft | 25 ft | None | No |
| Interior Conversion | By Right | 900 sq ft | — | None | No |
A-2 — Residence A-2
Single-family residential, moderate density
| Type | Approval | Max Size | Height | Parking | Owner Occ. |
|---|---|---|---|---|---|
| Detached ADU | By Right | 900 sq ft | 15 ft | None | No |
| Attached ADU | By Right | 900 sq ft | 25 ft | None | No |
| Interior Conversion | By Right | 900 sq ft | — | None | No |
B — Residence B
Two-family residential district
| Type | Approval | Max Size | Height | Parking | Owner Occ. |
|---|---|---|---|---|---|
| Detached ADU | By Right | 900 sq ft | 15 ft | None | No |
| Interior Conversion | By Right | 900 sq ft | — | None | No |
C — Residence C
Multi-family residential district
| Type | Approval | Max Size | Height | Parking | Owner Occ. |
|---|---|---|---|---|---|
| Interior Conversion | By Right | 900 sq ft | — | None | No |
Transit Stations
Properties near transit stations may qualify for parking exemptions.
Alewife
SUBWAY
Central
SUBWAY
Harvard
SUBWAY
Kendall/MIT
SUBWAY
Porter
SUBWAY
Porter Square (CR)
COMMUTER RAIL