ADU Construction Services in New Hampshire and Massachusetts
G.M. Roth Design Remodeling is a design-build firm based in Nashua, NH, offering accessory dwelling unit (ADU) construction services across southern New Hampshire and northeastern Massachusetts. With over 40 years of local experience, they operate as a full-service ADU contractor — managing zoning review, design, permitting, and construction under one roof.
Recent legislative changes in both states have made it easier for homeowners to add an ADU to their property. The Massachusetts Affordable Homes Act (2024) and New Hampshire's updated RSA 674:71–73 along with HB 577 (effective 2025) have expanded homeowner rights significantly. Under these laws, ADUs are now permitted by right in single-family zoning zones, with reduced restrictions on parking requirements and greater flexibility in size and layout. G.M. Roth Design Remodeling helps homeowners navigate these updated regulations to determine what is feasible on their specific property.
Types of ADUs They Build
G.M. Roth Design Remodeling works on several types of accessory dwelling units, depending on the homeowner's goals and property conditions:
- Attached ADU / In-Law Suite — Connected to the main home with shared utilities, suitable for aging-in-place or multigenerational living arrangements.
- Detached Backyard Cottage — A separate structure on the property, offering privacy for guests, family members, or flexible use as a home office or caregiver quarters.
- Garage Conversion ADU — Converting an existing garage into a complete living unit, either within or above the structure.
- Basement / Lower-Level Apartment — A cost-effective approach that makes use of existing space within the home.
Each ADU type serves different needs. Some homeowners pursue an in-law suite builder to house aging parents in a safe, accessible space. Others are interested in a detached ADU builder for adult children or long-term rental potential, depending on local town regulations. The firm holds Aging-in-Place (CAPS) certification, which informs their approach to accessible design.
Their Design-Build Process
Rather than requiring homeowners to coordinate separately with architects, engineers, and contractors, G.M. Roth Design Remodeling handles the entire process internally. Their ADU project workflow includes the following steps:
- Discovery & Site Review — Assessing the property and understanding the homeowner's goals within local ADU regulations.
- Zoning & Feasibility — Evaluating setbacks, septic systems, utilities, lot coverage, and applicable town bylaws.
- Concept Design & Budget Range — Developing layouts and 3D renderings alongside a realistic cost estimate.
- Architectural Plans & Engineering — Producing full drawings covering structure, mechanicals, and code compliance.
- Permitting & Approvals — Managing all permit submissions and communication with local authorities.
- Construction & Project Management — Overseeing the build with a dedicated project manager on site.
- Final Walkthrough & Warranty — Delivering the completed ADU move-in ready with ongoing support.
This integrated approach is intended to reduce the administrative burden on homeowners and keep the project on a clear timeline. Transparent pricing and detailed plans are part of their standard process.
G.M. Roth Design Remodeling serves a wide geographic area, including communities throughout the Nashua region of New Hampshire — such as Hudson, Merrimack, Bedford, Manchester, and Windham — as well as numerous towns in Massachusetts including Chelmsford, Lowell, Westford, Groton, Pepperell, and Marlborough, among others.
The company was founded in 1986 and is led by Gerry Roth, who holds CGR, CAPS, and CSL designations. The firm received the 2025 Guildmaster with Distinction award from Guild Quality, recognizing their customer service practices.