What is a French drain and how do I know if my yard needs one installed?

A French drain is a gravel-filled trench with a perforated pipe at the bottom that collects water from the soil and carries it away from where you don’t want it. You likely need one if water pools in your yard after rain, your basement gets wet, or one part of the lot stays soggy long after a storm. Around here we usually solve a wet basement from the inside, so let us look before you dig up the yard.

Here is the plain version. You dig a trench. You line it with fabric. You lay a perforated pipe, cover it with crushed stone, and slope it so gravity pulls the water downhill to a safe spot. The water seeps into the pipe through the holes and runs out the low end. That is the whole idea. Simple, and it has been done the same basic way for a long time.

People mix up two very different drains. A yard or “curtain” drain sits outside and moves surface or shallow groundwater across your lot. An interior French drain sits under your basement floor along the footing and feeds a sump pump. Same name, different jobs. If your real problem is a wet basement, the outside trench is often the wrong tool.

How to tell if your yard needs one

Walk the property after a hard rain. Look for water that stands for hours, a soggy low spot that never dries, or mud that creeps toward the house. Check your foundation too. Is water sitting against the wall? In New Hampshire that spot is usually disturbed backfill, the looser fill that got put back when the house was built. It drains slowly and holds water right where you don’t want it. Then winter comes. Frost heave pushes on the walls and the wet just makes it worse.

If water pools at the foundation and shows up inside, an outdoor yard drain alone rarely fixes the basement. We see it in the field. Exterior excavation waterproofing tends to fail in about two or three years, then you are paying again. Our durable fix for a wet basement is interior drainage feeding a sump pump, not a trench in the yard.

When you do not need one

Plenty of yards drain fine on their own. If the ground dries within a day, water runs away from the house, and your basement stays dry, you don’t need a French drain. Don’t let anyone talk you into one you don’t need. Sometimes the fix is grading, a downspout extension, or a clogged gutter. Cheap stuff first.

What this connects to inside

For a wet basement, the right answer is usually our Forever Dry System: full-perimeter interior drainage along the floor wall joint, a sump pump, a 12-mil wall vapor barrier, and a dehumidifier. It is guaranteed dry for life. Basement waterproofing runs $3,000 to $30,000. If your trouble is a dirt or low crawl space instead, that is crawl space encapsulation at $3,000 to $25,000, a different system, not the Forever Dry.

A few outdoor drainage jobs make sense, and some do not, and the only way to know is to look. We give a free inspection and a free estimate, and you get the quote within 24 hours. Financing is available through Hearth, subject to approval, and we make nothing on it.

While someone is at the wall, ask about the structural and foundation side too. Standing water and frost can crack a wall, and that is a separate repair. Our work is backed by the 603 guarantee.

For grading and surface-water basics, the U.S. Department of Energy’s Building America program (basc.pnnl.gov) has good plain guidance on keeping water away from a foundation. For how water damage and your home affect coverage, the Insurance Information Institute (iii.org) is a solid neutral read.

Ready to find out?

Call us at 603-610-1770 or book your free inspection. We will tell you whether you need a yard drain, an interior system, or just better gutters.

Related questions

Does a French drain fix a wet basement by itself? Usually not. An outdoor trench moves yard water, but a wet basement comes through the floor wall joint and the walls. For that we install interior drainage and a sump pump under the slab. We look first and tell you which one you actually need.

Will 603 dig up my yard to waterproof the basement? No. We don’t do exterior excavation waterproofing. In our experience it tends to fail in about two or three years. The durable fix is interior drainage feeding a sump pump, done from inside, with much less mess to your yard.

What does a basement waterproofing system cost? Our Forever Dry System runs $3,000 to $30,000. The price depends on how many feet of drain your basement needs and what shape the walls are in. The inspection and estimate are free, and you get the quote within 24 hours.

Do I need a backup sump pump? If your basement floods when the power goes out, yes. We use a battery backup. A charged backup battery can pump roughly a residential pool’s worth of water, about 15,000 to 20,000 gallons, before it needs power again.