ADU Builder in Portsmouth, NH
Custom Accessory Dwelling Units Built for Portsmouth Homeowners - From Design to Final Inspection
ADU Construction Services in Portsmouth, NH
Portsmouth's housing market is one of the most competitive on the Seacoast. Between rising property values, limited inventory, and a growing need for multi-generational living arrangements, homeowners are looking for smarter ways to use the land they already own. An accessory dwelling unit puts that space to work - whether it's rental income, a private suite for aging parents, or a dedicated home office that isn't crammed into a spare bedroom.
Under New Hampshire's updated ADU statute (HB 577, effective July 2025), Portsmouth must now allow both attached and detached ADUs by right in every residential zone. That means no conditional use permits, no special exceptions - just a standard building permit and the right team to get it built. Bradford Construction Management is a licensed ADU contractor serving Portsmouth, NH and the greater Seacoast region, delivering every project with commercial-grade project management and daily jobsite documentation.
We serve homeowners throughout Portsmouth, Newington, Rye, New Castle, Greenland, and the Kittery/York, ME border market.
Types of ADUs We Build in Portsmouth
Every property is different. We'll walk your lot, review your goals, and recommend the ADU type that makes the most sense for your budget, timeline, and how you plan to use the space. Here's what we build.
Detached Accessory Dwelling Units
A standalone structure on your property - completely separate from the main house. Detached ADUs offer the most privacy for both the homeowner and the occupant. Popular in Portsmouth for rental income and multi-generational living. Under HB 577, detached units are now allowed by right statewide.
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Attached ADUs and In-Law Suites
An addition that connects directly to your existing home. Attached ADUs are ideal when lot constraints or budget favor building onto what's already there. We design private entrances, separate living areas, and full kitchens and bathrooms so the space functions as a true independent unit - not just a remodeled room.
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Garage Conversions and Above-Garage ADUs
Convert an existing garage or build living space above it. This is often the most cost-effective path to an ADU because the foundation and structure already exist. Under NH law, existing structures - including garages that don't meet current setback requirements - can be converted to ADUs without zoning relief.
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Basement and Lower-Level ADUs
Transform underused basement space into a fully finished accessory dwelling unit. Basement ADUs maximize your existing footprint without changing the exterior of your home. We handle egress requirements, waterproofing, mechanical systems, and all the detail work that separates a legal, livable unit from a basic finish-out.
Discuss Your ProjectWhy Portsmouth Homeowners Choose Bradford Construction Management
Most contractors build your project and move on. We built an entire service model around not doing that.
Daily Photo Documentation
Every active jobsite is photographed every day. You see exactly what happened, what's next, and where your money went - without having to ask.
Commercial-Grade Project Management
Our leadership team managed large-scale commercial projects before applying that same discipline to residential work. Clear scopes, reliable schedules, and organized communication from start to finish.
Transparent Pricing
You get a detailed scope and clear pricing before work begins. We walk through every line item so there are no surprises. Change orders are documented and approved before anything changes. Explore financing options to see how we help homeowners plan their investment.
Lifetime Support Through Bradford Home Services
After the final walkthrough, we don't disappear. Our sister company, Bradford Home Services, provides ongoing maintenance, small repairs, and warranty follow-through for the life of your project. Zero abandoned clients.
NH ADU Permit Navigation
We handle Portsmouth zoning requirements, building permits, and inspections. From lot feasibility to certificate of occupancy, one team manages the paperwork so you don't have to.
Design-Build Under One Roof
No juggling separate architects, engineers, and contractors. One accountable team takes your project from initial concept through design, permitting, construction, and final inspection.
How Our Portsmouth ADU Process Works
From the first site visit to handing you the keys, here's what working with Bradford looks like.
Free Site Consultation
We visit your Portsmouth property to evaluate ADU feasibility - lot size, setbacks, utilities, and your goals. You'll leave with a clear picture of what's possible and a realistic budget range.
Design and Permitting
Our team prepares plans tailored to your property and handles the full Portsmouth building permit process. We manage the paperwork, coordinate with the city, and keep the timeline on track.
Construction
Licensed crews build your ADU on schedule with daily photo updates. You'll have access to our project management platform so you always know what's happening on site - no chasing down your contractor for answers.
Final Inspection and Handover
We walk through the completed unit together before final sign-off. After that, Bradford Home Services is here for ongoing maintenance, repairs, and warranty support.
ADU Pricing for Portsmouth, NH
Every ADU project is unique - pricing depends on size, configuration, site conditions, and finish selections. Our free ADU Lookbook includes detailed floor plans, exterior styles, and transparent pricing for every model we offer.
Portsmouth, NH ADU Zoning and Permit Requirements
New Hampshire's ADU laws changed significantly in 2025 with the passage of HB 577. Here's what Portsmouth homeowners need to know before starting an ADU project.
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ADUs Allowed by Right Under HB 577 (effective July 1, 2025), Portsmouth must allow one attached or detached accessory dwelling unit by right in every zone that permits single-family homes. No conditional use permits or special exceptions are required - just a standard building permit.
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Size Requirements Municipalities cannot restrict ADU size to less than 750 square feet. Maximum allowable size is 950 square feet unless Portsmouth authorizes a larger unit. This applies to total living space including kitchen, bath, and sleeping areas.
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Setbacks and Dimensional Standards ADUs follow the same setback, lot size, and dimensional requirements as the primary dwelling. Portsmouth cannot impose additional restrictions on a property simply because it includes an ADU.
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Existing Structure Conversions Existing structures, including detached garages that don't meet current setback or lot coverage requirements, can be converted to ADUs without zoning relief. This opens up options for many older Portsmouth properties.
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Owner Occupancy Portsmouth may require that the property owner live in either the primary dwelling or the ADU, but cannot dictate which unit the owner must occupy.
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Building Permits and Inspections Building permits are required for all ADU construction in Portsmouth. Bradford Construction Management manages the full permitting process on behalf of our clients - from application through final inspection and certificate of occupancy.
Portsmouth may have additional local requirements beyond state minimums. We verify current zoning details with the City of Portsmouth before every project. Have questions about what's allowed on your lot? Reach out for a free consultation.
What Our Clients Say
Bradford Construction was phenomenal on our multi-stage, 10-month complete rebuild. Rick and the whole crew surpassed any expectations we had going into the project.
Excellent customer service and quality work throughout project. Highly recommend!
Rick and his team did a great job on our home. Communication was solid throughout, we always knew what was happening and when. Quality of work is excellent. Would definitely recommend.
Frequently Asked Questions - ADUs in Portsmouth, NH
Serving Portsmouth and the Seacoast NH Region
Bradford Construction Management builds accessory dwelling units throughout Portsmouth and nearby Seacoast communities. We also serve homeowners across the greater Portsmouth area and beyond.
We also build ADUs in Andover, MA, Newburyport, MA, Ipswich, MA, and across the Merrimack Valley and North Shore.
Start Your Portsmouth ADU Project Today
Ready to add an accessory dwelling unit to your Portsmouth property? Whether you're exploring the idea or ready to break ground, we'll walk you through every step - from feasibility and design through permitting, construction, and ongoing support. One team, one point of contact, zero abandoned clients.