Amex Construction: ADU Builders Serving the South Shore of Massachusetts
Amex Construction is a Hanover-based design-build firm that specializes in accessory dwelling units (ADUs) across the South Shore of Massachusetts. They manage projects from initial concept through to final completion, offering homeowners a single team, a single contract, and a clearly defined process.
With Massachusetts' updated statewide ADU law now allowing many homeowners to build an ADU by right — without requiring a special permit — Amex Construction helps property owners navigate the opportunity while addressing the practical challenges that come with it, particularly around septic systems and local code compliance.
Their services cover a range of ADU project types, including new detached ADU construction, barn conversions, and basement in-law suite builds. As an ADU contractor operating under a design-build model, they handle both the design and construction phases internally, which is intended to reduce miscommunication and keep budgets and timelines more predictable.
A Four-Step Process for ADU Projects
Amex Construction follows a structured four-step approach to ADU development:
- Feasibility & Utility Review
- Preconstruction, Design & Permitting
- Site Work & Construction
- Final Inspection & Move-In
This process is designed to surface potential issues — especially septic-related ones — early in the project rather than after design work has already begun. At the feasibility stage, they review existing Title 5 reports, as-built plans, and bedroom counts, and bring in a septic engineer when the situation calls for it. If a septic system upgrade is required, it is priced and phased alongside the ADU from the start.
Amex Construction coordinates with septic engineers, the local Board of Health, and the building department so that septic design, ADU plans, and permits move forward together. This is intended to prevent homeowners from being caught between separate contractors and agencies managing different parts of the same project.
Why Septic Systems Are a Key Factor for ADU Projects in This Region
Across much of Southeastern Massachusetts, the septic system is often the primary constraint on whether an ADU project can move forward. Homes not connected to town sewer must demonstrate that their existing system can legally handle the additional flow that comes with adding a dwelling unit. If it cannot, an upgrade or full replacement is typically required before any permits are issued.
There are several specific considerations that Amex Construction addresses as part of their ADU work:
- Bedroom count and system capacity: Title 5 septic design is based on bedroom count rather than square footage. Adding bedrooms through an ADU can exceed a system's design flow, triggering an upgrade regardless of whether it was anticipated.
- Nitrogen-sensitive areas: Parts of the South Shore and Cape Cod fall within nitrogen-sensitive watersheds. Septic systems in these areas may require advanced nitrogen-reducing technology and are subject to stricter review standards, which adds engineering complexity and cost if not planned for from the beginning.
- Local Boards of Health: Each municipality has its own procedures, forms, and expectations when reviewing ADU-related septic work. Boards across Massachusetts are issuing ADU septic guidance tied to Title 5 and the new statewide ADU law, making local familiarity an important part of keeping a project on track.
Amex Construction handles excavation, system replacement or upgrade, and ADU construction as a single coordinated project. This approach is meant to avoid situations where a completed ADU cannot be legally occupied because septic approvals are still pending.
As an ADU builder with experience in site work and underground utility coordination, Amex Construction positions itself as a contractor suited to properties where the groundwork is as important as the structure built on top of it.