Accessory Dwelling Units (ADUs) in Southern New Hampshire
Custom ADU Builders in Southern NH & Northern Massachusetts
As housing costs continue to rise and families look for smarter ways to use their property, Accessory Dwelling Units — commonly called ADUs — are becoming one of the most popular home additions in New Hampshire.
Whether you’re planning a detached backyard cottage, an in-law apartment, garage conversion, or private living space for aging parents or adult children, Alphacon Building Group can help design and build an ADU that fits your property, your family, and your long-term goals.
We proudly build custom ADUs throughout Southern New Hampshire and Northern Massachusetts.
What Is an ADU?
An ADU (Accessory Dwelling Unit) is a secondary residential living space located on the same property as a primary home.
ADUs can be:
Detached backyard cottages
In-law apartments
Garage apartments
Above-garage suites
Basement apartments
Attached additions with private living spaces
Most ADUs include:
A bedroom or studio layout
Kitchen or kitchenette
Full bathroom
Private entrance
Separate living area
ADUs are ideal for:
Aging parents
Multigenerational living
Adult children returning home
Long-term rental income
Guest accommodations
Home office or flex space
New Hampshire’s New ADU Law Opens New Opportunities
New Hampshire recently passed major legislation expanding homeowners’ rights to build ADUs statewide. Beginning July 1, 2025, municipalities are now required to allow at least one ADU — including detached ADUs — anywhere single-family homes are permitted.
The updated law:
- Allows detached ADUs by right in many situations
- Prevents many municipalities from imposing excessive restrictions
- Allows ADUs to be converted from existing structures like garages
- Expands flexibility for homeowners and multigenerational housing
- Increases the maximum allowable ADU size in many cases
While local zoning, septic, setback, and permitting requirements still apply, the new law has made ADUs significantly more attainable for New Hampshire homeowners.
Why Homeowners Are Building ADUs
Multigenerational Living
Many families want aging parents close by while still maintaining privacy and independence. ADUs create a comfortable solution without the need for assisted living or purchasing a second home.
Rental Income Potential
A properly designed ADU can create long-term rental income and help offset mortgage costs.
Increased Property Value
Well-designed ADUs often add significant functionality and resale appeal to a property.
Flexible Living Space
Today’s ADUs can serve multiple purposes over time — guest house now, home office later, rental unit in the future.
Our ADU Design & Build Process
At Alphacon Building Group, we help homeowners navigate the entire ADU process from concept through construction.
Our services include:
- Site evaluations
- Preliminary layout planning
- Permit coordination
- Septic and utility coordination
- Structural planning
- Full construction management
- Interior finish selections
- Custom design solutions
Every property is different, and ADU construction often requires careful planning around zoning, setbacks, utility access, grading, and existing structures. Our team works closely with homeowners to create solutions that are both functional and compliant.
Types of ADUs We Build
Detached ADUs
Standalone backyard cottages or small homes separate from the primary residence.
Attached ADUs
Additions connected to the existing home with private entrances and living areas.
Garage Conversions
Transforming existing garages or barns into fully functional living spaces.
Basement Apartments
Converting unfinished basements into legal living spaces with kitchens and bathrooms.
Above-Garage Suites
Private apartments built above attached or detached garages.
Serving Southern NH & Northern MA
We proudly provide ADU construction services throughout:
- Nashua
- Hudson
- Windham
- Londonderry
- Bedford
- Hollis
- Amherst
- Salem
- Derry
- Merrimack
- And surrounding Southern NH communities
BBB A+ Rating
Fully Licensed and Insured
20 Years of Hands-On Experience
Start Planning Your ADU
Whether you’re exploring an in-law apartment for family, a detached backyard cottage, or an income-producing rental unit, Alphacon Building Group can help you understand your options and create a plan that works for your property and budget.
Contact us today to schedule a consultation for your New Hampshire ADU project.