Should I install a French drain to deal with water in my basement?

For a wet basement, the fix that lasts is an interior perimeter drain tied to a sump pump, not a yard-style French drain dug around the outside of your foundation. That interior system is the core of our Forever Dry System, and basement waterproofing with it runs $3,000 to $30,000. We do not dig up the outside of your house. In our field experience, exterior excavation jobs tend to fail in about 2 to 3 years.

Let’s back up to what a “French drain” even is. The term gets used two ways. Outside, it’s a gravel trench with a perforated pipe that carries surface water away. Inside, it’s a perimeter channel set in the floor that collects water at the wall and sends it to a sump. People hear “French drain” and picture the outside version. For a wet basement, the inside version is what keeps you dry.

Here is why the outside trench struggles around here. The dirt against your foundation is disturbed backfill. That’s the loose fill the builder pushed back in after the foundation went up. It drains slowly and holds water. So water pools right at the wall. NH frost heave then pushes against that wall through the winter. An exterior trench sits in that same trouble zone, and once it clogs or settles, you’re digging again. That’s our field experience, not a slogan.

The interior route works with the problem instead of fighting it. Water finds the weakest point. Usually that’s the floor wall joint, where the slab meets the wall. An interior perimeter drain catches the water right there, low and quiet, and routes it to the sump. The pump lifts it out. You stay dry.

The full Forever Dry System is the perimeter drain plus a sump pump (we size it at 1/2 hp per 120 feet of drain), a 12-mil wall vapor barrier, and a dehumidifier. It’s basement only. It’s 100% guaranteed to be dry for life, and the warranty transfers if you sell, as long as no one else touches the work. That guarantee is the whole point of doing it right the first time!

What drives the cost? Mostly how many feet of wall we have to drain, how your floor is poured, and whether your sump setup needs a backup. Basement waterproofing comes in at $3,000 to $30,000. We give you a free inspection, a free estimate, and a quote within 24 hours, so you see the number before you decide anything. If financing helps, we use Hearth, and we make nothing on it (subject to approval).

You might not need the whole system. If you have one weeping crack and a dry floor, that can be a crack injection job, not a full perimeter drain. We’ll tell you that at the inspection. We’d rather size it right than sell you more than the wall needs.

Two more things homeowners ask about. Sump backup is battery only. A charged backup battery can pump roughly a residential pool’s worth of water, about 15,000 to 20,000 gallons, which carries you through a storm if the power drops. And if your wet space is a crawl space rather than a basement, the answer is different. That’s crawlspace encapsulation, not Forever Dry, and it runs $3,000 to $25,000.

If you’ve got standing water, damp walls, or a musty smell, get eyes on it. We serve New Hampshire, Maine, and Massachusetts out of East Kingston, and we’ve been trusted by 5,000+ homeowners in New England. Call us at 603-610-1770 or book your free inspection. We’ll walk the basement with you and show you exactly what it needs.

Learn more about our basement waterproofing, crawl space services, and the 603 guarantee. For background on how soil and water move around a foundation, the U.S. Department of Energy’s Building America program is a solid neutral read (basc.pnnl.gov). For what water damage your homeowners policy does and doesn’t cover, see the Insurance Information Institute (iii.org).

Related questions

Does 603 install exterior French drains around the foundation? No. We don’t do exterior excavation waterproofing. In our experience those outside jobs tend to fail in about 2 to 3 years. The durable fix is interior perimeter drainage tied to a sump, which is what our Forever Dry System uses. See basement waterproofing.

Will an interior drain crack my basement floor? We open a channel along the perimeter where the slab meets the wall, set the drain, and patch it back in. The bulk of your floor stays as it is. We’ll show you the plan at the free inspection.

What if water is coming up in my crawl space, not the basement? That’s a different system. Crawl spaces get crawlspace encapsulation, a 12-mil wall and 20-mil floor vapor barrier with drainage matting, a sealed and dehumidified space, and a sump. It runs $3,000 to $25,000 and carries a 25-year warranty. See crawl space services.

How fast can I get a quote? The inspection and estimate are free, and we get your quote to you within 24 hours. Call 603-610-1770 or book your free inspection.