A newer house doesn’t mean a dry basement
Merrimack has some of the newest housing stock we work in, and we still pump water out of these basements every spring.
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Folks here tell us the same thing all the time. The house is from the eighties, so how can it have a water problem? Fair question. The answer is that the age of the house has almost nothing to do with it. What matters is the ground it sits in, and around here that ground holds water.
Two rivers, one town
Merrimack has the Merrimack River on one side and the Souhegan running right through it to meet it. The USGS gauges the Souhegan in town (USGS station 01094000, Souhegan River at Merrimack, NH), so the spring rise is on record rather than a matter of opinion.
A river valley means a high water table, and a high table means the ground under your slab is already wet before a drop of rain falls. The soil around your foundation makes it worse. When the house went up, a crew dug the hole, set the walls and pushed the same dirt back in. That backfill stays looser than the ground that was never dug. Loose soil drains slow and parks water against the wall.
Then March arrives. About 53 inches of snow comes down over a Merrimack winter (NCEI 1991-2020 normals, via Current Results, nearest station Nashua) and melts into ground still frozen a foot down. It can’t soak in. It runs sideways, finds the loose ring around your foundation, and comes up at the floor wall joint. Frost heave spent the winter working that joint open for it.
What it costs to waterproof a basement in Merrimack
$3,000 to $30,000 for a full system. The number moves on how much perimeter drain the basement needs, the state of the floor, and whether you add a battery backup.
Free inspection, free estimate, written quote in 24 hours. Hearth handles financing if you want it, subject to approval, and we don’t make a cent on that.
How the Forever Dry System keeps it dry
Full perimeter drain along the inside edge of the floor at the floor wall joint. One 1/2 hp sump pump per 120 feet of that drain. Vapor barrier on the walls. A dehumidifier so the air is dry, not just the slab.
We guarantee it. 100% dry for life or we come back free of charge, and it transfers to the next owner under our conditions. The sump system carries 3 years, batteries excluded.
Get the battery backup. The storm that floods you is the storm that kills the power, and a charged backup will move about a residential pool’s worth of water before it needs charging. Battery only. We don’t sell water-powered units.
We don’t dig up the outside. Exterior excavation fails in two or three years once the backfill settles again, and you pay for it with your yard. Interior drainage lasts because you can reach it and service it.
If your basement is dry, we will tell you it’s dry. One crack in an otherwise sound wall does not need a system. Fill the crack and don’t look back.
Merrimack: local context
Nearly nine in ten households here own their home, which is the highest we see anywhere in our service area. That changes what people want from us. Owners aren’t looking for a patch to get through the sale. They’re staying, and they want the thing fixed once.
The housing itself is mostly seventies and eighties build, so we’re working with poured concrete and block. That’s the easy part. Those walls take interior drainage cleanly and there’s no fieldstone and mortar to fight. What we do run into is that subdivision-era grading moved a lot of dirt, and the fill around those foundations is exactly the loose ring that holds water. Newer house, older problem. (Housing age and ownership figures are in the sources below.)
Everything on this page falls under basement waterproofing. Beyond that, basement finishing, crawl space encapsulation, foundation crack repair and radon mitigation are all work we do in Merrimack. Soft or bouncing floors overhead are a separate question, and sill beam replacement and lally columns cover the money side of it.
What we actually find in an eighties basement
The failure looks different in a newer house, so it’s worth knowing what to watch for. In a fieldstone basement the water seeps through the wall itself and you can see it darkening the stone. That’s not what happens here.
In a poured or block wall the water comes in at the seams. The floor wall joint first, because that’s a cold joint between two pours and it was never watertight to begin with. Then any tie holes or the gap where a lally column post meets the slab. You’ll see a damp line an inch or two up the wall, or a stain that runs along the base of the wall and stops.
The other one we see a lot in Merrimack is the pump that was fine for twenty years and isn’t now. Somebody dropped a pump in a hole when the house was built, no drain feeding it, and it handled the light years. Then a wet spring shows up and the water comes in somewhere the pit can’t reach. The pump isn’t broken. It just never had a drainage system behind it.
Frequently asked questions
My Merrimack house is from the 1980s. Why does it have a water problem at all?
Because the water table doesn’t care how old the house is. You sit between two rivers on ground that stays wet, and the fill around your foundation is loose enough to let water sit against the wall. A 1985 foundation in that ground gets just as wet as a 1925 one. The difference is your walls are poured or block, which are easier for us to work with.
How much does basement waterproofing cost in Merrimack?
$3,000 to $30,000 for the full system, driven mainly by how many feet of perimeter drain you need. Free inspection, free estimate, quote in writing inside 24 hours.
Will a sump pump on its own fix it?
Usually not. A pump only moves water that reaches the pit. With no drain feeding it, the water finds another way in and the pump sits there dry while your floor is wet. The drain does the work. The pump is the last step.
Do you excavate around the outside of the house?
No. We work from the inside. Digs fail in a couple of years when the soil settles back, and you’ve lost the landscaping for nothing.
We put in a sump when we built. Isn’t that enough?
Depends what’s feeding it. A lot of Merrimack houses got a pit and a pump at construction and nothing else. No perimeter drain, no barrier. That setup handles a damp corner and nothing more. If water is coming in twenty feet from the pit, the pump will never see it. We’d rather add the drain to the pump you already own than sell you a whole system you don’t need.
Does the Souhegan actually affect houses away from the river?
Yes, more than people expect. The river sets the water table for the valley around it, not just the lots on the bank. You can be a mile off the water and still have a table that comes up in April. What decides your basement is your elevation and your soil, not your distance from the bank.
What a recent customer said
Great team at 603. From the office people to the estimator (Corey) to the installation crew lead by Angel, they have done two jobs for me in my basement. The first was an install of a new sump basin and pump last fall. I liked it so much that I had them come back this July and install a replacement basin and pump for the other side of my basement. Nice job.
Gregg Maynard, 5 stars, Google review
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Sources
Souhegan River streamflow: USGS 01094000, Souhegan River at Merrimack, NH. Snowfall: NCEI 1991-2020 normals, via Current Results (nearest station Nashua, 52.9 in/yr). Housing age and tenure: US Census ACS 2023 5-year, tables B25035 (median year structure built, 1984) and B25003 (89% owner occupied). System components, warranty length and price range are 603 figures, owner confirmed.
