Concord basement waterproofing — local context
Concord sits right on the Merrimack River, which cuts northwest-to-southeast through the center of the city — and the USGS gage there (Merrimack River at Concord, site 01088400) drains a 2,300-square-mile basin, fed in town by the Contoocook at Penacook, the Soucook on the east, and the Turkey River. When spring snowmelt swells those rivers, water tables rise across the valley. The soil makes it worse: USDA-NRCS maps the river-side East Side as Windsor loamy sand, "excessively drained" with very high conductivity, so a high water table reaches your footing with nothing slowing it — and the western uplands as dense Paxton till, where water "may perch on the densic contact" late fall through early spring (USDA Official Series Descriptions). Concord is also one of only seven NH towns enforcing a freeboard rule, requiring a basement's lowest floor be raised above the base flood elevation (NH Municipal Association). We fix this with our interior Forever Dry System — full-perimeter drain, a sump per 120 ft, wall vapor barrier, and a dehumidifier — not exterior excavation, which is a short-lived fix. Basement waterproofing runs $3,000–$30,000.
What a recent customer said
This past winter, I purchased a small cottage in the Lakes Region of New Hampshire and, when the spring thaw hit, the basement flooded. I knew the water table was high in the neighborhood in which the cottage was located but I thought the sump pump in place would keep water intrusion to a minimum. When that did not prove to be the case, I got several estimates for basement waterproofing and settled on 603 Basement Solutions. The company did amazing work, installing their signature sump pump (a quiet workhorse), a dehumidifier with battery backup, and a trenching system around the basement perimeter, for a reasonable price that beat the other estimates, along with a waterproof guarantee. That basement is dry as a bone and has been ever since they completed their work! 603 Basement Solutions was efficient and professional every step of the way. Well worth the money!
Frequently asked questions
Why do Concord basements flood during the spring thaw?
Concord sits in the Merrimack River valley, fed by the Contoocook, Soucook, and Turkey rivers (USGS gage 01088400 drains a 2,300-square-mile basin). When snowmelt and rain swell those rivers, the water table rises across the valley. On the East Side's excessively drained Windsor loamy sand, that high water table reaches your footing fast; on the Paxton till of the western uplands, water can perch underground from late fall through early spring (USDA-NRCS). Either way, disturbed backfill holds water against your wall, so interior drainage to a sump — not just a re-grade — is what keeps a Concord basement dry.
Does Concord have special basement flood rules?
Yes. Concord is one of only seven New Hampshire communities that enforce a freeboard requirement, meaning a structure's lowest floor — including a basement — must be elevated a set number of feet above the base flood elevation (NH Municipal Association). New FEMA Flood Insurance Rate Maps for the Merrimack watershed of Merrimack County, including the Concord region, became effective January 23, 2026 (Concord Monitor / FEMA), so it's worth checking whether your property's flood designation has changed.
Do you dig up the outside of the foundation to waterproof a Concord basement?
No. We install our interior Forever Dry System — a full-perimeter drain, a sump pump (one per 120 feet of perimeter), a wall vapor barrier, and a dehumidifier — which captures and carries water to the sump from inside. We don't do exterior excavation waterproofing; in our experience it's a short-lived fix, while the interior system is the durable one that handles Concord's seasonal high water table.



