Garage Conversions: Lexington vs Waltham
How do garage conversions rules compare between Lexington, MA and Waltham, MA?
Lexington and Waltham have similar restriction levels.
Lexington, MA
Middlesex County
Garage conversions in Middlesex County are subject to local zoning bylaws and the MA State Building Code 780 CMR. Conversion to ADUs is now by-right under the 2024 Affordable Homes Act.
View full Lexington rules →Waltham, MA
Middlesex County
Converting a garage to living space in Waltham requires a building permit, zoning compliance, and may now qualify as an ADU under the 2024 Massachusetts Affordable Homes Act.
View full Waltham rules →Key Facts Comparison
| Fact | Lexington | Waltham |
|---|---|---|
| Building Permit | Required (780 CMR) | - |
| Ceiling Min | 7 feet | - |
| ADU Conversion | By-right under s.3A | - |
| Parking Replacement | Often required | - |
| Historic Review | Certificate of Appropriateness | - |
| Permit required | - | Yes, building permit |
| ADU pathway | - | By-right if under 900 sq ft as ADU |
| Code | - | 780 CMR MA Building Code |
| Ceiling minimum | - | 7 feet |
| Final step | - | Certificate of Occupancy required |
Highlighted rows indicate differences between cities.
Lexington FAQ
Can I convert my garage to a bedroom or ADU?
Yes with a building permit. ADU conversions are now by-right statewide under the 2024 Affordable Homes Act.
Do I need to replace parking?
Most towns require replacement parking, but ADU conversions have capped parking requirements under state law.
Waltham FAQ
Can I convert my Waltham garage to a bedroom suite?
Yes, with a building permit and compliance with MA Building Code for habitable space including egress, heating, and detectors.
Does a garage conversion count as an ADU?
Yes, if it becomes an independent dwelling. Under 2025 state law, garage-to-ADU conversions up to 900 sq ft are by-right.
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