Get your basement dry for good
Nashua sits in the Merrimack valley, and the low ground near the river holds water long after the rain stops.
Call 603-610-1770Get a free inspection
What it costs to waterproof a basement in Nashua
A full basement waterproofing system from 603 runs $3,000 to $30,000. Straight numbers, no surprises.
What moves the price is how much perimeter drain your basement needs, the shape the floor is in, and whether you add a battery backup. A short run along one wet wall sits at the low end. A full perimeter with a sump and a dehumidifier in a bigger Nashua home runs higher.
The inspection is free and so is the estimate, and you get a written quote within 24 hours. Financing is available through Hearth, subject to approval, and 603 does not make a dime on it.
Why Nashua basements get wet
The Merrimack runs the whole east side of the city, and the Nashua River comes in to meet it in the city. The USGS watches the Merrimack in town at the Nashua gauge (USGS station 01096508, Merrimack River at Nashua, NH), so the spring rise is measured, not guessed. Homes on the low ground near the rivers and the brooks that feed them sit closest to that water table.
Then there is the part nobody tells you. When your house was built, a crew dug a hole, set the foundation, and pushed the same dirt back in around it. That backfill never packs down like the ground that was never touched. It stays loose. Loose soil drains slow and holds water right against your wall, which is why the water shows up at the foundation and not out in the yard.
Winter makes it worse. Nashua averages about 53 inches of snow a year (NCEI 1991-2020 normals, via Current Results). All of it melts into that backfill in March and April, the ground is still frozen underneath, and the water has nowhere to go but sideways into your basement. Frost heave pushes on the walls all winter and opens up the floor wall joint while it’s at it.
That’s why a Nashua basement can flood every spring and stay bone dry in August. It isn’t the rain. It’s the water table.
How the Forever Dry System keeps it dry
The Forever Dry System is four parts working together. A full perimeter drain along the inside edge of the floor, right at the floor wall joint where most leaks show up. One 1/2 hp sump pump for every 120 feet of that drain, so the pump can actually keep up. A vapor barrier on the walls. And a dehumidifier, so the room stays dry and not just the floor.
We guarantee it. 100% dry for life or we come back free of charge, and that guarantee transfers to the next owner under our conditions. The sump pump system carries a 3-year warranty, batteries excluded, since batteries wear on their own schedule.
We also offer a battery backup, and it’s battery only. We don’t run a water-powered model. Power tends to fail in the exact storm that floods you, and a charged backup will move roughly a residential pool’s worth of water before it needs power again.
One thing we don’t do is dig up the outside of your foundation. We’ve watched those dig-and-coat jobs fail in about two or three years. The backfill settles again, the coating breaks down, and you’ve paid to tear up your yard for nothing. Interior drainage lasts because you can reach it.
And if your basement is dry, we’ll tell you that too. One crack in an otherwise dry wall doesn’t need a full system. Fill the crack and don’t look back.
Nashua: local context
Most Nashua houses went up in the seventies, so what we’re usually working with is poured concrete or block. That’s good news. Those are exactly the walls interior drainage and a vapor barrier are built for, and we’re not fighting the fieldstone and mortar you find in the older river towns.
Nashua is a city, though, and that changes the conversation. A lot of the housing stock here is two-family and three-family, and close to half of it is rented rather than owner occupied. So the first question is often who pays. If you own the building, a dry basement protects the whole structure and every unit above it. If you rent, the water is your landlord’s problem to fix, and we’re happy to talk to them directly. We’ve had that call plenty of times. (Housing age and ownership figures are in the sources below.)
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 Nashua. For what structural work actually costs, see lally columns and sill beam replacement.
Working in a city, not a field
Nashua is the second largest city in New Hampshire, and city lots change how the job runs. In a rural town we run the discharge line well out into the yard and forget about it. Here the yard is forty feet wide and there’s a neighbor on the other side of it.
So the discharge takes some thought. It has to carry water far enough from your foundation that it isn’t just circling back into the same backfill, and it can’t dump onto the property next door. That’s how neighbor disputes start, and we’ve been called in to fix a few of them. On a tight lot we’ll usually run it to the street side or tie it into existing drainage rather than aim it at a fence line.
Older city blocks also mean shared walls and shared basements. On a two-family or a three-decker, the drain has to be laid out around a basement that’s already carved up with tenant storage, a shared laundry, and mechanicals for three units. We work around that. It’s slower than an open basement and we’ll say so in the quote instead of finding out on day two.
Frequently asked questions
Why does my Nashua basement flood in the spring but stay dry in the summer?
It’s the water table under the Merrimack valley. About 53 inches of snow melts into ground that’s still frozen underneath, the river comes up, and the water rides that high table into your basement through the floor wall joint. By August the table has dropped and the same basement is dry. Nothing about the house changed.
How much does basement waterproofing cost in Nashua?
$3,000 to $30,000 for a full system. The length of perimeter drain is the biggest driver, then the floor condition and whether you want a battery backup. Free inspection, free estimate, written quote in 24 hours.
I own a two-family in Nashua. Is it worth waterproofing a rental basement?
Usually yes, and not for the tenants’ comfort. Water in a basement rots the sill and the framing that holds up every unit above it, and a musty smell moves through a multi-family fast. Fixing the water is cheaper than fixing the structure it wrecks. We’ll give you the same free inspection and the same written quote.
Do you dig up the outside of the foundation?
No. We waterproof from the inside. Exterior excavation fails in a couple of years once the dirt settles back, and it costs you your yard on the way. Interior drainage is the one that holds.
Where does the sump discharge go on a small Nashua lot?
Far enough from the foundation that it isn’t feeding the same backfill it just came out of, and never onto the neighbor’s property. On tight lots we usually run it toward the street or tie into drainage that’s already there. We’ll walk the line with you before we dig so there are no surprises about where the water ends up.
What a recent customer said
My husband and I can’t say enough great things about 603 Basement Solutions and their employees. After having two incidents of water in our basement in the early spring of last year, we knew that we had to do something better than dealing with it manually by ourselves. We researched a few companies and ended up getting two quotes. We selected 603 and couldn’t be happier with our choice.
Debora Speight, 5 stars, Google review
Ready to get started?
Free inspection, free estimate, and a written quote in your hands within 24 hours.
Sources
Merrimack River streamflow: USGS 01096508, Merrimack River at Nashua, NH. Snowfall: NCEI 1991-2020 normals, via Current Results (Nashua station, 52.9 in/yr). Housing age and tenure: US Census ACS 2023 5-year, tables B25035 (median year structure built, 1974) and B25003 (56% owner occupied). What the system contains, what it costs and how long it is covered for are all 603’s own numbers.
