A home addition needs a building permit before work starts, and the permit process has a clear order: zoning check, drawings, application, plan review, inspections and a final sign-off. This guide walks through six steps for homeowners in Massachusetts and southern New Hampshire. Rules differ by town, so confirm every point with your local building department.
Norman Builders is a design-build home builder and remodeler in Newton, NH. Permits and inspections are part of how we run our home additions: as the builder, we handle the permitting and inspections for the job.
Which Addition Projects Need a Permit?
Any project that extends the footprint, adds a story or changes the roofline of a one or two family home needs a building permit. That covers room additions, bump-outs, second-story additions, dormers, attached garages and garage conversions. Structural changes inside the house, such as removing a bearing wall to join old and new space, are part of the same permit.
- Building permit: foundation, framing, roof, insulation, windows, stairs and egress.
- Electrical, plumbing and gas permits: new circuits, a new bathroom, a kitchen extension or gas appliances.
- Mechanical permit: new heating or cooling, ductwork or a mini-split for the added space.
Small cosmetic work such as painting or replacing flooring usually does not need a permit, but your town sets the exact list. If you are unsure, ask.
How to Get a Permit for an Addition in 6 Steps
Step 1: Check Zoning and Setbacks
Before you draw anything, find out what your lot allows. Your town's zoning bylaw or ordinance sets setbacks (how close you can build to each property line), maximum lot coverage and height limits. A design that crowds a setback may need a variance from the zoning board. In Massachusetts that process comes from M.G.L. c. 40A; in New Hampshire it comes from RSA 674:33. Wetlands, historic districts and septic systems can add their own review, so ask the town which boards will see your plan.
Step 2: Get Drawings From a Designer or Builder
Most towns want a floor plan with dimensions, a site plan showing the addition on your lot, elevations and a wall section. A designer, architect or design-build team can prepare them. Anything that carries load, such as a long span or a second story, may need engineering.
Step 3: Prepare the Application
Gather the signed application, the drawings, proof of ownership and the contractor's information. Check what your building department requires, because forms differ from town to town.
Step 4: Submit the Application
Many towns accept applications online, and others want paper at the counter. Ask whether zoning or other boards must approve first. In Massachusetts, a licensed construction supervisor or, for an owner-occupied one or two family home, the homeowner can pull the building permit. Homeowners who pull their own permit lose the protections of the state Home Improvement Contractor law (M.G.L. c. 142A) for that work. Contractors doing this work on an existing owner-occupied home generally must be registered Home Improvement Contractors, so ask to see the registration.
Step 5: Pay the Fee and Wait for Plan Review
The building department reviews the plans against the state code. Massachusetts uses the 10th edition of 780 CMR, based on the 2021 IRC and IECC with state amendments. New Hampshire adopted the 2024 IRC effective July 1, 2026, with a concurrency period through December 31, 2026 when either the 2021 or 2024 code may be used, and keeps the 2018 IECC, according to the New Hampshire Building Officials Association. The reviewer may send questions or ask for changes before approving.
Step 6: Schedule Inspections and Close Out
Inspections happen at set points: foundation, framing, rough electrical and plumbing, insulation, and a final. Do not close walls before the inspector signs off on what is behind them. Plumbing and gas work in Massachusetts must be done by licensed plumbers and gas fitters with permits from the local inspector. In New Hampshire, RSA 319-C:15 lets a homeowner do electrical work in a single-family home they own and live in, and the work still has to meet code. Keep every signed card and the final certificate with your house records, since buyers and lenders may ask for them.
Local Rules in Massachusetts and New Hampshire
- Enforcement is local: the state code applies statewide, but each town issues permits and runs inspections, and practices differ.
- Historic districts: in Massachusetts, a town with a historic district under M.G.L. c. 40C may review exterior changes before the building permit.
- Accessory dwelling units: since July 1, 2025, RSA 674:72 requires New Hampshire towns with zoning to allow one accessory dwelling unit by right with a single-family home. An in-law addition still needs building permits.
To see where we build, visit where we work, or read our town pages such as Andover, MA and Newton, NH.
What an Addition Costs Beyond the Permit
The permit is one line in a bigger budget. For the full picture, see how much a home addition costs, or try the home addition cost calculator. When you are ready to talk through your lot and plans, request an estimate or call (978) 833-7337.
Frequently Asked Questions about Home Addition Permits
Do I need a permit for a home addition?
Yes, in almost every case. A new room, a bump-out, a second story or an attached garage changes the footprint, height or structure of the house, and that is building-permit work in Massachusetts and New Hampshire. Electrical, plumbing and heating work in the addition usually needs its own permits. Your town building department makes the final call, so ask before you plan.
What happens if you build an addition without a permit?
A town that learns of unpermitted work can stop the job and charge for an after-the-fact permit. Inspectors cannot approve what they cannot see, so you may have to open finished walls. Buyers and their lenders can ask whether the addition was permitted, and an insurer may treat a claim tied to that work differently. Ask your insurer how it handles unpermitted work.
How much does a residential addition permit cost?
Fees follow each town's schedule, and many towns tie them to the cost of the work. According to This Old House (2026, quoting Angi), a building permit for a remodel or addition commonly runs $500 to $2,500. Your town's fee schedule gives the real number.
How long does the permit review process take?
It depends on the town and how complete your plans are. Some towns turn a simple application around quickly, and others take weeks, especially when a zoning board or conservation commission has to weigh in first. Ask the building department for its current review time when you call, and build that wait into your schedule.
