Foundation Repair and Basement Waterproofing in Derry, NH

Water

Where the water comes from in Derry

The sump pump rule. Chapter 122 of the town code says, "The connection of sump pumps to the sanitary sewer system is strictly prohibited," and also bars roof downspouts, foundation drains, areaway drains and other surface or groundwater sources from the sewer (§122-29). Public Works' "Guide to Sump Pump Connections" explains that "Town sewers are not designed to carry the additional flow from sump pumps," and that the overload causes "sewer backups in the streets and other homeowner's basements." Sump water "must discharge to the ground surface outside of the building, to a stormwater drain, or to a natural outlet," and the guide says "DO NOT pump storm water onto sidewalks or streets." The town does flow monitoring, may video-inspect mains, and may make random inspections to find illicit sump pump connections; Public Works is at 603-432-6144 (sump pump guide). A sump that empties into a basement drain or laundry line has to be rerouted to one of those allowed outlets.

Your sewer line. The owner pays for repairs and maintenance of the building sewer from the house to the public sewer, including the tee in the town main, and only Derry-licensed utility contractors may connect to it (Chapter 122). About 30% of residents are on municipal sewer, with rural areas on septic (Summary of Existing Conditions). The stormwater chapter adopted in 2008 sets civil penalties of up to $1,000 a day for illicit discharges (Chapter 131).

Flood zones. The town's flood zones page says Derry's GIS shows the 100- and 500-year flood zone layers, the building department holds the FEMA flood maps for Rockingham County effective May 17, 2005, the office can't issue flood-zone letters, and an elevation certificate needs a licensed land surveyor (Flood Zones). For your own address, search FEMA's Flood Map Service Center.

The hazard plan. Derry's Hazard Mitigation Plan, adopted by the Town Council on February 3, 2026 and approved by FEMA on April 1, 2026, notes that development is concentrated around Beaver Lake and Beaver Brook and Hornes Pond and Brook, that about 100 detention ponds designed for 50-year storms could cause localized flooding, and that, as of 2020 state data, the town had six residential repetitive-loss flood properties (Hazard Mitigation Plan). The town's master plan inventory says most of Derry's soils are till over bedrock, suited to basements and septic systems, with limited shallow bedrock (Summary of Existing Conditions).

Wetlands. Prime wetlands carry a 150-foot buffer, with special exceptions only in the outer 75 feet and no dredging or filling in the wetland itself (prime wetlands; buffer). In poorly drained soil areas, structures and fill are not allowed*(empty: delete this clause; the sentence then reads "In poorly drained soil areas, structures and fill are not allowed (…)")* (poorly drained soils). Check those lines before an outside drain or regrading job.

Radon

Radon in Derry basements

The state's August 2023 radon data brief puts Rockingham County among the three highest in New Hampshire, with half of tested homes at 7.9 pCi/L or higher; statewide, about 37% of 32,747 homes tested from 2007 to 2021 were at or above 4 pCi/L (NH radon data brief). The state Radon Program says there is no safe level of radon and offers free test kits at (603) 271-1708 (NH Radon Program). Test before finishing a basement; if a mitigation system is needed, the state says to retest after it's installed and every two years after that (testing your home).