Additions
In-Law Suite & ADU Guide for Massachusetts Homeowners
By Rogerio Alves, Founder & Master Framer
July 1, 2026 · 7 min read
An in-law suite or accessory dwelling unit (ADU) in Massachusetts typically costs $80,000 to $250,000+ depending on whether you convert existing space (basement/garage) or build an addition, and whether it includes a full kitchen and bath. Recent MA law changes have made ADUs easier to permit in many towns. RS Development Group designs and builds them to code — call (774) 512-3176.
What makes a space a legal in-law suite?
- A code-compliant means of egress (proper doors/windows).
- Its own bathroom, and usually a kitchen or kitchenette.
- Proper separation, utilities, heating, and often a separate entrance.
- Compliance with local zoning and the Massachusetts building code.
Convert existing space or build an addition?
Converting a basement, garage, or bonus room is usually the most affordable path when the space and ceiling height allow. When it doesn’t, a dedicated addition or detached ADU gives more privacy and flexibility. We’ll walk your home and lay out the most cost-effective, code-legal option for your family.
Ready to start your project?
Get a free, no-obligation estimate from a licensed Massachusetts contractor.
Call (774) 512-3176About the author — Rogerio Alves
Rogerio Alves is the founder and lead contractor of RS Development Group, a licensed (MA HIC #216507) construction company he started in 2008. A master framer by trade, he and his team serve 100+ Massachusetts communities with structural framing, additions, roofing, siding, and full general contracting.
