Portsmouth’s housing has had a long time to settle. The median home here was built in 1958, and plenty are far older than that in the historic parts of the city. A foundation that has stood for decades has usually moved a little, and a crack is often just the evidence of that. The question that actually matters is not whether there is a crack, it is whether it is still moving.
What it costs to repair a foundation crack in Portsmouth
Non-structural crack injection runs on the lower end and carries a 10-year warranty against leakage through the treated area. Structural crack injection with epoxy, used where the crack is doing real work holding the wall together, carries a 10-year warranty on the structural bond. We will tell you which one your crack needs after we look at it, not before.
Cosmetic crack or structural crack
A thin, straight vertical crack that has not changed in months is usually cosmetic, concrete shrinks slightly as it cures and a hairline crack is a normal result. A crack that is wide enough to fit a coin, runs stair-step through block joints, or is paired with a bowing or leaning wall is a different problem and needs a different fix.
We check for the second kind before we ever recommend the first. An injection seals a crack; it does not straighten a wall that is already moving.
How we actually fix it
For a non-structural crack, we inject polyurethane or epoxy resin the full depth of the crack, sealing it against water and stopping it from spreading. For a crack that is part of a structural problem, we address what is causing the movement first, that might mean power posts, a wall brace, or in some cases helical piers, and treat the crack itself as part of that larger fix rather than in isolation.
Frequently asked questions
Is a crack in my foundation always a big problem?
No. Most foundation cracks are cosmetic and stable. What matters is whether it is actively leaking, growing, or paired with other signs like a door that suddenly will not close right or a wall that looks like it is leaning.
How do I know if a crack is getting worse?
Mark both ends with a pencil and the date, and check back in a few months. If it has grown past the marks, it is active and worth a call. If nothing has changed, it is more likely stable.
Can you fix a crack from outside instead of inside?
We work from inside the basement for injection repairs. There is no need for exterior excavation on a straightforward crack repair.
Will the repair be visible?
The injection line itself is visible unless the wall gets a finish afterward, but the crack stops leaking and stops growing either way.
What a recent customer said
603 Basement Solutions put in a perimeter drain system, repaired 2 foundation cracks, and installed a vapor barrier in my basement. What you see in the photos are quick snapshots of a job well done. What you don’t see is a team of professionals that took the time from the first moment they stepped into my house to fully understand my needs and expectations. Everyone from the sales engineer to the office staff to the installation team were kind, professional, and honest. Would highly recommend.
Jon Martell, 5 stars, Google review
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Sources: Census ACS 2023 5-yr (B25035) for median year built. Warranty terms per the founder-confirmed warranty matrix. Review quoted from a public 603 Basement Solutions Google review.
Common questions about foundation cracks
- Why is my house sinking into the ground? Is there any way to repair it without tearing down the house?
- Would you rather have a house with a full basement or on a slab?
- A potential 6-floor residential property has too many thin lally columns in the basement. Are they safe, and can they be fixed?
- Are Ramset nails more likely to create a crack in a residential
- Are surface honeycombs on a concrete column dangerous?
- Are vertical or zig-zag cracks in a masonry / brick exterior wall something to worry about?
- By how much did your house value go down after fixing a foundation issue?
- Can a cracked home foundation be fixed?
- Can a house collapse from foundation issues?
- Can an old house foundation be repaired one room at a time?
- Can I have my concrete foundation repaired while I live in my home?
- Can stone masonry be used as a foundation?
Portsmouth foundation crack repair — local context
Foundation crack repair runs $1,000–$3,000 at 603 Basement Solutions, and Portsmouth's ground and housing stock are why so many older homes need it. Portsmouth sits in Rockingham County on the Presumpscot Formation — a late-Pleistocene glaciomarine deposit of blue-gray marine silt and clay (not sand) that Wikipedia notes was laid down below sea level, then lifted more than 300 feet by isostatic rebound. That soft, fine-grained clay shifts under footings with moisture and frost, opening cracks. Per NeighborhoodScout's ACS data, roughly a third of Portsmouth homes (32.5%) predate 1940 — among the oldest stock in the country — and the South End around Strawbery Banke holds dozens of 17th-to-19th-century Colonial, Georgian and Federal houses, many on the rubble/fieldstone foundations 603 specializes in. We inject non-structural cracks under a 10-year transferable warranty; structural cracks get carbon-fiber straps at $850 each. No crack-cost guide exists — see our foundation crack repair hub.
What a recent customer said
603 Basement Solutions put in a perimeter drain system, repaired 2 foundation cracks, and installed a vapor barrier in my basement. What you see in the photos are quick snapshots of a job well done. What you don't see is a team of professionals that took the time from the first moment they stepped into my house to fully understand my needs and expectations. Everyone from the sales engineer to the office staff to the installation team were kind, professional, and honest. Would highly recommend. Thanks 603 Basement Solutions!
— Jon Martell (5★)
Frequently asked questions
Why do so many Portsmouth foundations crack?
Portsmouth sits on the Presumpscot Formation, a glaciomarine deposit of blue-gray marine silt and clay (Wikipedia, "Presumpscot Formation"). That soft, fine-grained clay — not sand — swells and shrinks with moisture and frost, which moves footings and opens foundation cracks. It's a different mechanism than sandy soil, so the fix is about controlling water and stabilizing the wall, not just patching.
My Portsmouth home is pre-1940 — does that change the repair?
Often, yes. Roughly a third of Portsmouth homes (32.5%) were built in 1939 or earlier (NeighborhoodScout, ACS-derived), among the oldest stock in the country. Older Seacoast houses — common in the South End and around Strawbery Banke — frequently sit on rubble or fieldstone foundations rather than poured concrete, which 603 Basement Solutions specializes in. We assess the foundation type before recommending injection or structural reinforcement.
How much does foundation crack repair cost in Portsmouth?
At 603 Basement Solutions, foundation crack repair runs $1,000–$3,000. Non-structural cracks are sealed by injection and carry a 10-year transferable warranty; structural cracks are reinforced with carbon-fiber straps at $850 each. We don't publish a separate crack-cost guide — the scope is set after an on-site assessment of the crack and foundation.
