Who Builds Home Additions in Derry, NH That Actually Fit Your House?
Sean Ryan & Son builds home additions in Derry, NH and across Rockingham County — room additions, in-law suites, and second stories, all framed and finished in-house rather than farmed out to subs. Most projects run 3 to 6 months depending on scope, and yes, you can usually keep living in the house while it happens.
By Sean Ryan, Owner, Sean Ryan & Son Carpentry & General Contracting · Last updated September 2026
What Does a Home Addition in Derry, NH Actually Involve?
Depends on what you're solving for. Some Derry homeowners need one more bedroom. Some need a whole separate living space for a parent moving in. A room addition off the back of the house is a different job than a full second story, and both are different from an in-law suite with its own entrance, kitchenette, and bathroom.
We handle the whole thing ourselves — design input, framing, electrical and plumbing coordination, insulation, drywall, and finish work — instead of handing pieces off to a rotating cast of subcontractors. That matters more on additions than almost any other project, because an addition has to tie into an existing roofline, existing siding, and an existing foundation that was built decades before yours was a consideration.
Why Do Families Add an In-Law Suite Instead of Moving?
Because moving is expensive and an in-law suite solves the actual problem. We've built a handful of these in Rockingham County over the years for the same reason every time: a parent or adult child needs their own space, but everyone still wants to be under one roof, close enough to help but not on top of each other.
Here's the part most people don't think about until we bring it up. In New Hampshire, adding a bedroom to a house often triggers a review of the septic system, since NH's subsurface disposal rules size a system to the house's bedroom count. If your addition adds a bedroom and your septic was designed for a three-bedroom house, that gets checked before anything gets framed. It's a five-minute conversation early on, not a surprise halfway through the job — but only if the contractor knows to have it.
How Much Does a Home Addition Cost in the Derry Area?
Most Derry-area additions we build land somewhere between $180 and $350 per square foot, with the range driven by what's inside the space. A simple room addition with no plumbing sits at the low end. An in-law suite with a full kitchenette and bathroom, or a second story that requires structural work on the floor below it, sits toward the top. A 500-square-foot addition, as a rough midpoint, usually runs somewhere in the $110,000–$150,000 range once you include permits, finishes, and site work — though the only honest number is one built off a walkthrough of your specific house.
Who Handles Permits and Inspections for a Derry Home Addition?
We do, start to finish. Home additions in Derry require a building permit through the Town's Code Enforcement / Building department, and depending on the scope, that can mean separate electrical and plumbing permits plus a zoning setback review if the addition changes your building footprint. We pull the permits, schedule the inspections, and deal with the town directly, so you're not the one on hold trying to figure out which form applies to your project.
Where Do We Build Home Additions Around Derry and Rockingham County?
Derry's our home base for this kind of work, along with Londonderry, Auburn, Chester, and Windham. We also build additions further out across Rockingham County — Atkinson, Raymond, Epping, and Exeter — and into the Seacoast towns like Hampton and Portsmouth when the project's the right fit. If you're not sure whether your town's in range, just ask; it's usually a shorter drive than people expect.
Who Builds Home Additions Near Derry, NH?
Short answer: a general contractor who's licensed, insured, and willing to put the scope in writing before a single stud gets cut. Sean Ryan & Son is registered with the State of New Hampshire and fully insured, and every addition starts with a written contract covering scope, timeline, and payment schedule — no verbal handshake agreements. We also offer financing options for homeowners who'd rather spread the cost out than pay for the whole addition up front, and every project starts with a free, no-pressure consultation at your house.
Ready to Talk Through Your Addition?
Contact Sean Ryan & Son for a free home addition consultation, or take a look at our home additions services page for more on how we scope a project. If a kitchen or bathroom remodel is part of the plan too, we've also got dedicated guides on kitchen remodeling in Derry and bathroom remodeling in Derry.
Frequently Asked Questions
1. How much does a home addition cost in the Derry area?
Most projects fall between $180 and $350 per square foot depending on whether the space includes plumbing, like a kitchenette or bathroom. A full walkthrough is the only way to get a number specific to your house.
2. Do you offer free home addition consultations?
Yes. We come to your house, look at what you're working with, and talk through options before any pricing gets discussed.
3. Do you handle permits and inspections for an addition?
Yes, we pull every permit the project needs through the town and manage the inspection schedule ourselves, including zoning review if the addition changes your footprint.
4. Are you insured and bonded, and do you provide a written contract?
Yes to both. We're registered with the State of New Hampshire, fully insured, and every job starts with a written contract laying out scope, timeline, and payment terms.
5. Do you offer financing for a home addition?
Yes, we offer financing options for homeowners who'd rather spread payments out than pay the full cost upfront. Ask about it during your free consultation.
Visit or Call Us
Sean Ryan & Son Carpentry & General Contracting 1 Pheasant Lane Atkinson, NH 03811 Phone: 603-362-8230 Text: 603-300-6214 Serving Derry and surrounding areas including Londonderry, Auburn, Chester, Windham, Atkinson, and the greater Rockingham County area.
