Accessory Dwelling Units (ADUs) in Massachusetts
Backyard cottages, garage conversions, basement apartments and attached additions, taken from feasibility through permitting to certificate of occupancy by one design-build team.
- Fixed-Price Contracts
- Traditional & Modular
- Family-Owned Since 2006
At R.H. Blanchard Contract & Design, we help Massachusetts homeowners unlock the full potential of their property through thoughtfully designed and expertly built Accessory Dwelling Units. Whether you’re creating space for family, generating rental income, or increasing long-term property value. We provide a complete, start-to-finish solution from feasibility and design through permitting and construction.
One Team, Start to Finish
Design, permitting, trades and construction all sit under a single design-build contract, so nothing falls between contractors.
Designers and Builders Together
Our designers and builders bring decades of experience to every remodel, and they work the project as one team.
Licensed & Insured in Massachusetts
A Massachusetts-licensed general contractor, fully insured, family-owned and working in local homes since 2006.
Transparent Communication
One point of contact, regular updates, and a written scope and timeline before any work begins.
What Is an Accessory Dwelling Unit?
An ADU is a secondary residential unit located on the same property as a primary home. In Massachusetts, evolving zoning laws and housing initiatives have made ADUs one of the most powerful tools available to homeowners. We help you determine what’s possible on your property and what makes the most financial sense.
ADUs Can Take Several Forms
- Detached backyard cottages
- Garage conversions
- Basement apartments
- Attached additions
A Streamlined Path From Concept to Certificate of Occupancy
Four stages, the same on every ADU, so you always know what happens next.
Feasibility & Budget
We evaluate your property, zoning, utilities, and layout and set a realistic budget range.
Design & Fixed Pricing
We develop layouts, coordinate engineering and code compliance, then issue a fixed-price contract.
Permitting & Approvals
We handle local zoning approvals, building permits, and all coordination with municipalities.
Construction
Dedicated project management, clear communication, high-end craftsmanship, and a clean site.
Get An ADU Feasibility Estimate
Tell us about your property and what you’d like to build. We’ll evaluate what’s possible and show you a realistic budget range. We make every effort to reply to all inquiries within one business day. If you need immediate assistance, call the number below.
Our Address
1323 South St, Andover, MA 01810
Our Telephone
(978) 479-4607
Two Ways to Build Your ADU
Both routes deliver high-quality, code-compliant ADUs. The right choice depends on your priorities.
Traditional ADU Construction
For homeowners who want full customization, we offer ground-up and renovation-based ADU construction.
Ideal For
Unique property layouts, historic homes, tight zoning, high-end finishes, or structural modifications.
Advantages
Fully customizable design, seamless integration with existing home, flexibility in size, layout, and materials.
Modular & Prefabricated ADUs
We partner with leading manufacturers like KBS Builders to deliver high-quality modular ADUs. As your local GC, we manage site work, foundation, utility connections, modular set, finish integration, and final inspections through occupancy.
Ideal For
Faster project timelines, controlled construction costs, efficient repeatable designs.
Advantages
Reduced construction duration, factory-built quality control, less on-site disruption.
Why Work With R.H. Blanchard?
Massachusetts ADU Expertise
We understand local zoning, permitting, and building codes including 780 CMR and municipal-specific requirements that make ADU projects uniquely complex.
Design-Build Model
One contract, one unified team. No friction between designer and contractor. We manage the entire process, reducing risk and keeping your project on schedule and on budget.
Fixed-Price Contracts
We provide fixed-price construction budgets after the design phase so you know exactly what you're building and what it costs before a shovel hits the ground.
Modular & Traditional Options
We build both traditional stick-built ADUs and partner with leading manufacturers like KBS Builders for modular/prefab, giving you flexibility on timeline and cost.
Real-World Experience
Top 1% of Massachusetts contractors (BuildZoom Score 175). 5-star reputation. Owner directly involved in every project. We bring accountability that larger firms can't match.
ADU Cost in Massachusetts
Understanding cost is critical when planning an ADU. Below are realistic pricing ranges based on current Massachusetts market conditions. Actual costs vary based on home and site conditions.
~550 sq ft
Compact backyard cottages.
$325k to $375k
~750 sq ft
One-bedroom standalone unit.
$450k to $550k
~900 sq ft
Two-bedroom or extended floor plan.
$550k and up
Interior Conversion or Addition
Basement, garage, or attached addition.
$150k to $350k
Pricing is influenced by scope, site conditions, utility requirements, and finish level. We provide fixed-price budgets after your feasibility and design phase.
What to Know Before You Build
ADU projects involve more than construction. They require strategic planning. We help clients navigate:
Zoning & Setbacks
Lot-specific zoning restrictions and setback requirements.
Owner Occupancy
Owner-occupancy requirements where applicable.
Parking Regulations
Local parking minimums for ADU additions.
Utility Capacity
Sewer, water, and electrical service availability.
Fire Protection
Sprinkler and alarm requirements per code.
Energy Compliance
Insulation standards and energy code requirements.
Our goal is to identify risks early and control costs before construction begins.
ADU Builders Serving the North Shore & Greater Boston
Andover
Garage conversions, basement apartments, and attached additions. We navigate Andover’s zoning bylaws, utility upgrade requirements, and architectural integration.
North Andover
Detached and attached ADUs on larger residential lots.
Newburyport
Detached ADUs, outbuilding conversions, and high-end coastal or historic integrations. We focus on architectural character and septic/sewer constraints.
West Newbury & Newbury
Larger lots with strong potential for detached backyard cottages. We evaluate septic capacity and design for long-term property value.
Amesbury
Rental-income ADUs and multigenerational housing. ROI-focused planning and cost vs. value alignment.
Boston
Basement ADUs, rear additions, and compact urban layouts. We specialize in navigating strict Boston zoning, fire protection requirements, and utility limitations.
Also serving Bedford, Beverly, Burlington, Chelmsford, Dracut, Lowell, Malden, North Reading, Reading, Tewksbury, Wakefield and surrounding communities.
What Our Clients Say
Our clients are the catalyst for our growth and success.
ADU Questions, Answered
An Accessory Dwelling Unit (ADU) is a secondary residential unit located on the same property as a primary home. ADUs can take the form of detached backyard cottages, garage conversions, basement apartments, or attached additions. In Massachusetts, evolving zoning laws have made ADUs one of the most powerful tools available to homeowners.
ADU costs in Massachusetts vary based on type and size. Detached ADUs (new construction) typically range from $325,000–$375,000 for ~550 sq ft, $450,000–$550,000 for ~750 sq ft, and $550,000–$750,000+ for ~900 sq ft. Attached or interior conversion ADUs generally range from $150,000–$350,000. Final costs depend on site conditions, utility requirements, and finish level.
Yes. ADUs in Massachusetts require local zoning approvals and building permits. Requirements vary by municipality and depend on the ADU type, lot size, setbacks, and utility capacity. R.H. Blanchard manages the full permitting process, including local zoning approvals, building permits, and coordination with municipalities and inspectors.
The most common ADU types in Massachusetts include detached backyard cottages, garage conversions, basement apartments, and attached additions. The best type for your property depends on your lot size, zoning, existing structure, and goals. We evaluate your property and help you determine what is feasible and financially sensible.
ADU timelines depend on type and complexity. Traditional site-built ADUs typically take 9–18 months from feasibility through certificate of occupancy, including design, permitting, and construction. Modular ADUs can have shorter construction timelines due to factory fabrication, though permitting timelines remain similar. We provide realistic schedules during the feasibility phase.
A traditional ADU is built on-site, offering full customization, seamless integration with your existing home, and flexibility in size, layout, and materials. A modular ADU is factory-built and set on your site, offering faster construction timelines, controlled costs, and consistent quality control. R.H. Blanchard builds both types and helps you choose the best option for your property and budget.
Yes. Generating rental income is one of the most common reasons homeowners build ADUs. Massachusetts ADU regulations vary by municipality, and state legislation has been expanding ADU rights statewide. We help clients evaluate rental income potential and ensure full compliance with applicable regulations.
Yes. R.H. Blanchard manages the full permitting and approval process for ADU projects across Massachusetts, including local zoning approvals, building permits, coordination with municipalities and inspectors, and 780 CMR building code and energy code compliance. We handle the complexity so homeowners can focus on their goals.
Ready to Build Your ADU?
Schedule a no-obligation consultation. We’ll evaluate your property, walk you through what’s possible, and show you a realistic budget range.
Our Address
1323 South St, Andover, MA 01810
Our Telephone
(978) 479-4607