Last updated: September 24, 2026
What affects the price
Building an ADU involves several moving parts that shape your total investment. The final figure depends heavily on whether you choose a prefab unit or a custom build from the ground up. Site conditions are another major factor; if your property requires extensive grading, utility trenching, or foundation work, costs will climb. You also have to consider your choice of finishes, like high-end appliances or custom cabinetry. Navigating local permit fees and impact assessments also adds to the total.
About this service
A contractor oversees the physical build, managing the subcontractors, materials, and daily construction progress. They are responsible for making sure the structure is built according to the approved plans and local safety standards. You need a contractor when you have your designs finalized and are ready for the actual building phase to begin. They act as the primary point of contact for all site activity.
Frequently asked in Portsmouth
What is the cost of an accessory dwelling unit in Portsmouth?
What ADU services are available in Portsmouth?
Does AccessoryDwellingUnit Services operate in New Hampshire?
What is an ADU quote in Portsmouth?
What is involved in accessory dwelling unit construction in Portsmouth?
What types of prefabricated accessory dwelling units are available in Portsmouth?
What is an ADU unit in Portsmouth?
Also serving nearby: Norfolk · Chesapeake · Hampton · Newport News · Virginia Beach
More on this: HUD ADU resources — ADU policy and financing research.
Service area details
Serving all of Portsmouth — population 96,793; about 2,906 residents per square mile across 33.3 sq mi. ZIP codes covered include 23701, 23702, 23703, 23704, 23705, 23707, 23708, 23709.
Neighborhoods served in Portsmouth: Olde Towne, Cradock, Waterview, Olive Branch, Truxtun — and every surrounding area.
Areas we serve
Browse by state, then city.
