How New Hampshire Plans to Make Building ADUs Easier for Everyone

Homeowners in Amherst, New Hampshire, have new reasons to think bigger about their properties. Thanks to changes in state law, adding an accessory dwelling unit (ADU) has become easier and more rewarding than ever. With the updated ADU regulations taking effect statewide, the process of designing, permitting, and building these small but valuable living spaces is simpler and faster.

What’s Changed for ADUs in New Hampshire

Under the state’s new ADU law, which took effect on July 1, 2025, homeowners gain more flexibility and fewer barriers when adding an accessory dwelling unit to their property. The law now guarantees the right to build one ADU—either attached or detached—on any lot that already allows single-family homes. That means Amherst residents no longer need to go through conditional use permits, special exceptions, or lengthy zoning reviews to gain approval.

In practical terms, this change streamlines the process and removes uncertainty. If you own a single-family home in Amherst, you can now move forward confidently with plans to add an in-law suite, backyard cottage, or tiny home, knowing that state law supports your right to build.

The law also eliminates additional zoning hurdles. Municipalities can no longer enforce stricter lot size, frontage, or design requirements for ADUs than what’s already required for the main home. Detached units are now fully permitted, allowing homeowners to take advantage of underused land or existing outbuildings for new living spaces.

Why Amherst Homeowners Are Taking Notice

Amherst has always been known for its scenic neighborhoods, historical homes, and small-town charm.  However, like much of southern New Hampshire, the area faces growing demand for flexible and affordable housing options. The updated ADU regulations address that demand directly by making it easier for residents to create additional housing without changing the character of their neighborhoods. For many Amherst homeowners, this means new opportunities such as:

Multi-generational living – Create a private space for aging parents or adult children while keeping everyone close to home.

Rental income potential – With no familial-occupant requirement, property owners can lease their ADUs to tenants, providing steady income and helping offset rising costs of living.

Maximized space – Converting garages, barns, or unused areas into fully functional living units helps homeowners maximize property utility.

What the New ADU Regulations Allow

The 2025 ADU law includes multiple key updates that make these projects far more accessible across New Hampshire, including:

Detached ADUs by right – Homeowners can now build a detached structure—such as a standalone cottage or converted garage—without additional zoning variances. ‍

Larger unit sizes – ADUs may be up to 950 square feet in size, and local regulations cannot restrict them below 750 square feet. That’s enough space for a comfortable one- or two-bedroom layout.

No occupancy restrictions – The previous rule requiring family occupancy has been removed. Homeowners can rent their units to anyone.

Simplified utilities – ADUs can use existing septic and water systems if they meet the same standards as the main home, and a separate electrical service can be installed if desired.

Conversions allowed – Existing garages, barns, or other outbuildings can be converted into ADUs even if they don’t meet current setback or lot coverage requirements.

Designing & Building Your ADU in Amherst

Meetinghouse Builders offers full design-build services for homeowners ready to take advantage of these new opportunities. From concept to completion, our team helps you navigate every step of the process. We create detailed 3D renderings, construction plans, and custom design solutions that fit your property and lifestyle.

Whether you’re envisioning a detached tiny home behind your main house or a finished in-law suite within your existing footprint, we manage all aspects of design, permitting, and construction. Our experience working with local zoning boards and understanding state ADU regulations ensures a smooth process from start to finish.

Start Your ADU Project With Meetinghouse Builders

Transform your property potential with a beautifully designed accessory dwelling unit. Meetinghouse Builders creates seamless, fully customized ADU solutions for Amherst, NH, homeowners who want practical space, modern design, and lasting quality. Contact us today to schedule a free consultation and explore your home’s possibilities under New Hampshire’s new law.