Londonderry basements, and why the newest houses still get wet
The housing here is the newest in our service area, the ownership rate is among the highest, and we still pump water out of these basements every spring.
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Median build year is around 1985 and roughly seven in ten homes are detached single family. That should be the easy end of our work, and in some ways it is. Poured concrete and block walls, no fieldstone, no lime mortar. But a 1985 foundation sits in the same disturbed soil as a 1905 one, and the water does not check the date on the permit.
Orchard land, and what happens when you build on it
A lot of Londonderry went up on former farm and orchard ground, subdivided and graded in the seventies and eighties. That history shows up in basements.
When a site is cut and graded wholesale, the topsoil comes off, the lots get shaped to drain toward the road, and each foundation hole gets backfilled with whatever came out of it. That backfill stays looser than the undisturbed ground beside it for the life of the house. It drains slowly and it holds water right against the wall.
Which is why entire streets here behave the same way. If three of your neighbors are running sump pumps, that is not coincidence, it is the grading plan.
Beaver Brook drains the town south toward Pelham, where the USGS picks it up (USGS station 010965852, Beaver Brook at North Pelham, NH). Notice the gauge is downstream of you. Londonderry is high ground, so your water is your own snowmelt and rain sitting in your own soil, not a river coming up over its banks.
About 53 inches of snow falls over a winter here (NCEI 1991-2020 normals, via Current Results, nearest station Massabesic Lake). It melts in March into ground still frozen underneath, travels sideways, and arrives at the floor wall joint, the cold seam between your wall pour and your slab that frost heave has been prying at all winter.
What it costs to waterproof a basement in Londonderry
$3,000 to $30,000 for a full system. Drain length is the main driver, then floor condition and whether you add a battery backup.
Free inspection, free estimate, written quote inside 24 hours. Hearth handles financing if you want it, subject to approval, and we make nothing on it.
How the Forever Dry System keeps it dry
Full perimeter drain at the floor wall joint. One 1/2 hp sump pump per 120 feet of drain. Vapor barrier on the walls. Dehumidifier so the air is dry, not just the slab.
100% dry for life or we come back free of charge, transferable to the next owner under our conditions. Sump system carries 3 years, batteries excluded.
Get the battery backup. The storm that saturates the ground takes the power with it, and a charged backup moves about a residential pool’s worth of water before it needs a charge. Battery only, no water powered units.
We do not dig up the outside. Those jobs settle and fail inside two or three years and cost you the landscaping.
And if your basement is dry with one crack in it, we will fill the crack and leave you alone. That is not a system job and we will not dress it up as one.
The builder sump, and why it stopped keeping up
This is the basement waterproofing page. If your problem is upstairs of the water, we also do foundation crack repair, crawl space encapsulation, basement finishing and radon mitigation around Londonderry. For what structural work actually costs, see lally columns and sill beam replacement.
The house came with a pit and a pump. No perimeter drain, nothing feeding it, just a hole in the corner of the slab. For twenty or thirty years that was fine, because the water happened to arrive near the pit. Then a wet spring comes and water shows up fifteen feet away, and the pump sits there dry while the floor is soaked.
That pump is not broken. It never had a drainage system behind it. Adding the drain to the pump you already own is usually the cheaper answer, and it is the one we will quote first if it fits your basement.
What a finished basement hides
Plenty of Londonderry houses have a finished lower level, put in either by the builder or by an owner somewhere along the way.
The trouble with a finished basement is that it removes your early warning. Studs and drywall go up against a foundation wall, and from then on you cannot see the wall. Water that would have shown as a damp line on bare concrete now soaks into the bottom plate and the insulation instead, and the first you know about it is a smell on the stairs.
That smell is moisture in the wood and the insulation, and mold grows in that moisture. It is not a mystery and it is not fixed by a bigger dehumidifier or an air freshener. We open a small section, look at what is behind it, and tell you honestly whether it is a drainage job, a demolition job, or both. You should hear that at the estimate rather than halfway through the week.
If you are planning to finish a basement here, dry it first. Frame over a wall that takes water and you have sealed the problem in behind the drywall where you cannot reach it.
The cheap things to try before you call us
We would rather tell you this up front than take money for a system you did not need.
Walk outside during a hard rain and watch your downspouts. If they are dumping beside the foundation, extend them and see what changes over a season. Look at whether the ground still slopes away from the house for the first six feet, or whether forty years of settling has tipped it back toward the wall, which is extremely common on lots of this age.
Surface water is cheap to fix. Groundwater is not. Sorting out the free stuff first tells you which one you actually have, and if it turns out to be groundwater, we will still be here.
Frequently asked questions
My house is from the eighties. Why does it have a water problem?
Because the age of the house is not the variable. The soil around the foundation and the height of the water table are. A 1985 poured wall in loose backfill on high ground gets just as wet as an old one. What your build year does buy you is an easier fix, because poured and block walls take interior drainage cleanly.
Everyone on my street has a sump pump. Is that normal here?
Yes, and it tells you something. Subdivisions were graded as a single site, so every foundation on the street sits in comparable backfill with comparable drainage. Streets tend to behave as a unit.
How much does basement waterproofing cost in Londonderry?
$3,000 to $30,000 for a full system, mostly a function of drain length. Free inspection, free estimate, written quote in 24 hours.
Do you dig around the outside?
No. Interior only.
What a recent customer said
I had a great experience working with 603 Basement Solutions. The estimate was a smooth process and fair price, the work was scheduled quickly and the workers were efficient and focused.
Margo Valdes, 5 stars, Google review
Ready to get started?
Free inspection, free estimate, and a written quote in your hands within 24 hours.
Sources
Beaver Brook streamflow: USGS 010965852, Beaver Brook at North Pelham, NH. Snowfall: NCEI 1991-2020 normals, via Current Results (nearest station Massabesic Lake, 52.8 in/yr). Housing age and tenure: US Census ACS 2023 5-year, tables B25035 (median year structure built, 1985), B25003 (85% owner occupied) and B25024 (69% single unit). Prices, warranty and system specification are 603’s own, confirmed by the owners.
