Home › New Hampshire › Portsmouth
Foundation Repair and Basement Waterproofing in Portsmouth, NH
Portsmouth's draft 2024 hazard plan names the Historic District among the places most at risk from coastal flooding, sea-level rise and groundwater intrusion, in a city where about 38% of homes were built before 1940. Call (978) 800-2819 or use the form. A person reads every request and replies with what happens next.
- Free for homeowners
- City and state rules on this page
- The South End to Pease
Ask About Basement Service in Your Area
Tell us about the basement and what the water is doing. A person reads it and replies with what happens next.
Please add your name, a 10-digit phone number and a valid email.
Your request didn't go through on our end. Please call (978) 800-2819 so it isn't lost.
Too many requests have come from this connection in a short time. Please call (978) 800-2819 and we'll take it from there.
We couldn't finish the spam check. Wait a moment and send it again, or call (978) 800-2819.
Basements in Portsmouth
What's the basement problem?
Waterproofing & Drainage
Wet walls, seepage at the floor joint and spring water in the basement, handled with interior drains, exterior work or both.
Sump Pumps
New pits, replacement pumps and battery backups, with the discharge going somewhere your town allows.
Foundation Cracks & Repair
Leaking cracks, bowing or settling walls and failing mortar in old fieldstone, with an engineer brought in when the job is structural.
Crawl Spaces & Finishing
Damp crawl spaces sealed up, and dry basements turned into finished space with the right permits.
Not sure what it needs?
(978) 800-2819Tell us whether the water comes with rain, snowmelt or high tide, and we'll help you sort out what kind of job it is.
Permits
Permits and rules for basement work in Portsmouth
Permits come from the Inspection Department at City Hall, 1 Junkins Avenue (603-610-7243), and are filed on the city's Viewpoint permitting portal (Inspection Department). Its FAQ is clearer than most: "New construction and general renovation work requires the issuance of a building permit," including "Creating new rooms or spaces within a structure" and "Structural changes or repairs." Painting, flooring, insulating and similar ordinary repairs are exempt until their total cost exceeds $3,000, and ordinary repairs never include altering a structural beam or required egress (Inspection FAQ). A finished basement is new space, so it needs a permit.
- Inspection Department
- City Hall, 1 Junkins Ave, 603-610-7243
- Apply online
- Viewpoint
- Alterations
- $8 per $1,000 of renovation cost (fee page updated October 18, 2023)
- Without a permit
- 200% of the fee or $300, whichever is greater
- Storm drain
- Clean foundation and footing drain water allowed
Posted fees. The city's building permit fee page, updated October 18, 2023, prices alterations and renovations at $8 per $1,000 of renovation cost, with no basement or foundation line. A re-inspection is $100, and work done without a permit costs 200% of the fee or $300, whichever is greater. Interior renovations to a single-family home skip zoning review.
Codes and contractors. Permits are issued under the NH State Building Code (the IRC as adopted by NH) (RSA 155-A:2), and through December 31, 2026 they may be filed under either the 2021 or the 2024 codes (state code concurrence). "In New Hampshire, contractors do not need to be licensed," says the Attorney General's office, which advises references, proof of insurance and a written contract with the scope, materials, total price and payment schedule, and warns against deposits over half the price (NH AG). Over $5,000, the contract must include the RSA 359-G notice on resolving defects (RSA 359-G). Plumbing and electrical work need licensed trades unless an owner does it in their own single-family home (Mec 300; RSA 319-C). Digging outside needs a free Dig Safe ticket at least 72 hours ahead, and within 250 feet of public waters, an NHDES shoreland permit may apply (protected shoreland).
Last verified November 2026. Fees, restrictions and deadlines on this page are due for re-checking by January 2027. New England Basement Pros is a referral service. We don't pull permits or do basement work; the contractor files the permit.
Water
Where the water comes from in Portsmouth
Tides, storms and groundwater. The city's Natural Hazard Mitigation Plan Update 2024 is still a draft, with its adoption date blank (draft 2024 hazard plan). It names the Historic District among the areas at greatest risk from "coastal flooding, sea level rise, and groundwater intrusion," and says hurricanes and related storms bring "flooding of ponds, rivers, streams, roads and basements." On December 23, 2022, a surge of nearly three feet pushed the tide to 12.5 feet at Seavey Island; on January 13, 2024, a 9.6-foot high tide with a two-foot surge, rain and snowmelt caused widespread flooding, and Strawbery Banke saw unprecedented flood damage to historic buildings. The draft plans for 1 to 1.7 feet of sea-level rise by 2050.
The Historic District
Named in the draft plan for coastal flooding, sea-level rise and groundwater intrusion.
North and South Mill Ponds
Both listed in the draft plan as recurring or high-potential flood areas, along with the South End.
Peirce Island, Little Harbour and Sagamore Creek
Also on the draft plan's list of recurring or high-potential flood areas.
As of June 2024, the draft counts five repetitive-loss buildings with $88,096.05 paid, and 40 flood insurance losses paid since 1978. The city's Floodplain District covers FEMA flood areas plus its own "extended flood hazard areas"; the city suggests MapGeo as a first check and FEMA's Flood Map Service Center as the official source (floodplain regulations). Check both before you finish a basement here.
Where the pump water goes. Portsmouth's code says it outright: §16.204(C) allows uncontaminated flows from foundation drains, footing drains and crawl-space pumps into the storm drain system, while illicit connections are barred with fines of up to $1,000 a day (Chapter 16). Sump water still can't go into the sanitary sewer under state rules (Env-Wq 704), and the oldest parts of the sewer system are still combined, with three combined overflows left (sewer collection system). We didn't find a storm-drain connection permit process, so ask Public Works how a line to the street should be made.
Near the water. Around wetlands over 10,000 square feet, including most tidal areas, the city keeps a 100-foot buffer where new construction, ground disturbance and fill or soil removal need a City Conditional Use Permit, with no cutting in the first 25 feet (wetland buffer). Exterior excavation near the water starts with the Planning Department.
Portsmouth's homes
Nearly four in ten homes built before 1940
A 2014 housing study for the city's 2015 Master Plan found about 38% of Portsmouth's homes built in 1939 or earlier and about 62% before 1970, with a median year built of 1954 against 1979 for Rockingham County (Housing Existing Conditions, ACS 2008–2012).
In the Historic District, certain exterior changes need a Certificate of Approval from the Historic District Commission, and HDC applications can add at least a month to a project (Historic District Commission; Inspection FAQ). A new bulkhead, window well or exterior drain there should go to the Planning Department early, before the contractor books the dig.
Radon
Radon in Rockingham County basements
We didn't find a city radon figure. Rockingham County is among New Hampshire's three highest counties, with half of the homes tested there from 2007 to 2021 at 7.9 pCi/L or more; statewide, about 37% of tested homes were at or above 4 pCi/L (NH DHHS data brief, August 2023). The state's Radon Program gives residents free test kits and says to test the lowest livable area, usually the basement (NH Radon Program). New Hampshire doesn't license mitigation contractors, so ask for national certification.
FAQ
Portsmouth basement questions
Can foundation drain water go into Portsmouth's storm drains?
Clean water can. Chapter 16 of the city code allows uncontaminated flows from foundation drains, footing drains and crawl-space pumps into the storm drain system, while illicit connections can bring fines of up to $1,000 a day. Sump water may never go into the sanitary sewer under state rules. Ask the city how a physical connection to a storm drain has to be made.
Does finishing a basement need a permit in Portsmouth?
Yes. The Inspection Department's FAQ says new construction and general renovation need a building permit, including creating new rooms or spaces and structural changes or repairs. Even ordinary repairs need one once their total cost passes $3,000.
What happens if basement work starts without a permit?
The city's fee page, last updated October 18, 2023, charges 200% of the permit fee or $300, whichever is greater. Renovations are otherwise $8 per $1,000 of renovation cost.
Which Portsmouth areas flood most?
The city's draft 2024 hazard mitigation plan names North Mill Pond, South Mill Pond, the South End, Peirce Island, Little Harbour and Sagamore Creek, and records widespread tidal flooding on December 23, 2022 and January 13, 2024.
What does it cost me to use New England Basement Pros?
Nothing. Asking is free for homeowners; the contractor prices the job, and the price and contract are between you and them.
Nearby