Basement Waterproofing Cost in New Hampshire (2026)
The most useful thing to know before you call anyone: no New Hampshire basement waterproofer publishes a fixed price for the work, and almost none will quote one over the phone. The job is priced after a free in-home inspection, because the number depends on how much water you have, where it is coming in, and how far around the basement the fix has to run. Anyone who gives you a flat figure sight unseen is guessing.
This page is an independent, sourced cost guide. We do not sell waterproofing and we do not take placement fees. Every figure below is labeled national or NH, dated, and tied to a source you can open and read. Where the only number available is a homeowner's report, we say so and link the thread, because a single Reddit post is not a company price list.
The numbers that actually exist
There are two kinds of figures worth looking at: national third-party ranges for "basement waterproofing" as a category, and individual quotes New Hampshire homeowners have reported publicly. They are not the same thing, and they do not always agree.
| Source | Scope | Figure | National or NH |
|---|---|---|---|
| This Old House (2026) | Basement waterproofing, general | ~$3,000 to $7,000 | National |
| Modernize (2026) | Basement waterproofing, general (at or above industry average) | ~$8,000 to $16,000 | National |
| r/newhampshire homeowner report (2026) | Interior drain + sump, quoted by 603 Basement Solutions | ~$16,000 | NH |
| r/newhampshire homeowner report (2026) | Same scope, quoted by Erickson Foundation Solutions | ~$40,000 | NH |
| r/newhampshire homeowner report (2026) | Drain, sump, and a new slab, quoted by Basement Improvements LLC | ~$12,000 | NH |
| r/newhampshire homeowner report (2026) | Larger scope (see below), quoted by TC Hafford Basement Systems | ~$43,000 | NH |
The two national ranges come from reviews of Groundworks, the national consolidator whose nearest branch is in Hooksett, NH. This Old House puts general basement waterproofing at roughly $3,000 to $7,000. Modernize puts it at roughly $8,000 to $16,000 and describes Groundworks specifically as pricing at or above the industry average. Read those as the national category band, not as a New Hampshire quote.
The four NH figures come from one r/newhampshire thread in 2026, where homeowners shared what local companies bid on their jobs. Two of them are close to apples-to-apples. A homeowner reported about $16,000 from 603 Basement Solutions and about $40,000 from Erickson Foundation Solutions for the same scope: an interior perimeter drain and a sump. That is a wide spread for the same described work, which is exactly why you collect more than one quote.
A third homeowner reported about $12,000 from Basement Improvements LLC for a drain, a sump, and a new concrete slab. The fourth reported about $43,000 from TC Hafford Basement Systems, and that one is not comparable to the others. The TC Hafford bid covered a much bigger job: an interior drain plus a new four-inch slab, a wall membrane, two sump pumps, and a SaniDry dehumidifier. A bigger scope costs more. The $43,000 is not a "same job, higher price" data point, and you should not read it as one.
What moves the price
The reason these numbers swing from twelve thousand to forty-something is that "basement waterproofing" is not one product. The bid is built from parts, and the parts that matter most are:
- Perimeter length. Interior drainage is usually priced by the linear foot of basement wall it runs along. A small section under one wet wall is a fraction of a full perimeter.
- Water source. Surface water at one bulkhead is a different (and cheaper) problem than a high water table pushing through the whole slab. Crack injection at one wall, the lower-cost end, is not the same job as a full interior drain.
- Interior drain plus sump versus exterior excavation. Most NH waterproofers solve chronic water with an interior perimeter drain feeding a sump pump, which is the spread you see in the reports above. Digging out the foundation from the outside to seal and drain it is a larger, costlier job and is quoted separately.
- The slab. Some bids include breaking out and re-pouring concrete (the Basement Improvements and TC Hafford reports both did). A new slab is its own line and pushes the total up fast.
- The dehumidifier. A dedicated unit like the SaniDry in the TC Hafford bid is an add-on, not a given. Whether one is in the quote changes the bottom line.
- The warranty. A transferable lifetime guarantee is worth more than a one-year fix, and companies price for it. Confirm what the warranty is before you compare totals.
Compare quotes on scope, not on the bottom line
The single mistake that costs NH homeowners money here is reading the bottom-line number and picking the lowest. The $16,000 and the $40,000 reports were for the same described scope; the $12,000 and the $43,000 were for completely different jobs. A total only means something once you know exactly what it buys.
Before you compare two quotes, line them up part by part and ask of each one:
Once the two quotes describe the same work, the price difference is real and you can act on it. Until then, you are comparing a sedan to a pickup.
A note on who is quoting
The companies in the homeowner reports are different kinds of business, which is part of why their numbers differ. 603 Basement Solutions is a locally owned East Kingston firm that installs its own named system and handles radon in-house. Erickson and TC Hafford install the national Basement Systems product line as dealers. Groundworks, the basis for both national price ranges, is a national consolidator headquartered in Virginia Beach, VA, with a patented product line and a nationally backed warranty. Its corporate BBB profile shows 741 complaints closed in three years, about 69 percent of them service or repair (accessed June 2026). None of that makes one better than another for your basement; it does mean their pricing models and their warranty service work differently, so weigh the quote against the company, not in isolation.
If you want our scored, sourced read on which of these companies fits which job, we rank them by metro. For the Exeter area, see our verified ranking of basement waterproofing on the NH Seacoast. For the two pairings that come up most in cost questions, see 603 vs Groundworks and 603 vs Erickson. How we verify and score every figure is laid out in our methodology.
Sources
- This Old House, Groundworks review (national, 2026): basement waterproofing roughly $3,000 to $7,000. thisoldhouse.com
- Modernize, best foundation companies / Groundworks (national, 2026): roughly $8,000 to $16,000, at or above the industry average. modernize.com
- r/newhampshire homeowner reports (public, 2026): ~$16,000 from 603 Basement Solutions and ~$40,000 from Erickson for an interior drain and sump; ~$12,000 from Basement Improvements LLC for a drain, sump, and new slab; ~$43,000 from TC Hafford for a larger scope (interior drain, new four-inch slab, wall membrane, two sumps, and a SaniDry dehumidifier). reddit.com/r/newhampshire
- Groundworks corporate BBB profile (national, accessed June 2026): 741 complaints closed in three years, about 69 percent service or repair. bbb.org
- Company figures (ratings, systems, warranties) verified June 2026 from Google Business Profiles, BBB, and company websites; see each company profile.
Compare the companies head to head: 603 vs Groundworks.