Last updated: October 20, 2026. General information, not engineering advice. Local codes, soil and slope vary.
Search for either name and you will find the two used almost interchangeably, and sometimes with different meanings. This guide sorts out what each term usually means, how a curtain drain works, and when a drain in the yard is the right tool for a wet basement and when it is not.
The short answer
A curtain drain is a type of French drain: a gravel-filled trench with a perforated pipe, placed between a source of water and the thing you want to keep dry, and sloped so the water runs off to a safe outlet. Fine Homebuilding describes the idea as intercepting surface runoff and groundwater before it reaches the foundation. A French drain is the broader family, and some sources (Angi, for one) use the name for deeper drains inside the basement as well. So the useful question is not “curtain or French?” but “where does this drain sit, and what water is it meant to catch?”
A curtain drain is meant for runoff coming toward the house. It is not a fix for water rising through the floor from a high water table. Fine Homebuilding suggests an interior drain with a sump pump where the water table is high.
Why the two names get mixed up
The sources do not agree on vocabulary, which is a big reason homeowners get confused:
| Source | How it uses the terms |
|---|---|
| Wikipedia | A French drain is a trench of gravel or rock, with or without a perforated pipe, that redirects surface water and groundwater. A curtain drain is a version that is covered with soil so it stays hidden. |
| InspectAPedia | A French drain is an outdoor buried line that carries water away from a building. A footing drain sits outside the foundation wall at the footing. A perimeter drain is the one cut into the floor inside. |
| Angi (updated Aug 4, 2026) | A curtain drain is shallow and handles surface water. A French drain is deeper and is described mostly as an interior system for basements that flood from below. |
Angi and InspectAPedia therefore use “French drain” for different locations. When you get a quote, ask the contractor to say where the pipe goes (yard, footing or inside the basement) rather than relying on the name. Our guide to French drain costs covers the three kinds and their prices.
How a curtain drain works
- Position. It sits between the water source and the foundation, so water moving toward the house reaches the drain first.
- Trench and fill. Fine Homebuilding describes a trench about 18 to 24 inches deep, with a perforated pipe, gravel over it, and landscape fabric (not cheap weed barrier) to keep silt out of the gravel.
- Slope and outlet. The trench slopes downhill to an outlet where the water will not cause a new problem, such as a lower part of the yard, a dry well or a rain garden (the outlets Wikipedia lists for French drains in general).
- Gutters stay separate. Fine Homebuilding advises not to connect gutter downspout lines to the perforated pipe, but to run them alongside it.
That article dates from 2007, so read its dimensions as one example, not as a current standard.
What a published specification looks like
Numbers vary by purpose and place. As one example, Oregon’s septic rules (OAR 340-71-220) describe curtain drains that protect a drainfield from groundwater. A county guide summarizing them calls for a trench at least 12 inches wide, 4-inch perforated pipe with the holes facing up, at least 10 inches of drain media over the pipe, filter fabric on top, and a uniform pipe grade of 0.2 to 0.4 feet of fall per 100 feet. That rule is written for septic systems, not basements, but it shows how specific a properly designed curtain drain is. Wikipedia gives a typical pitch of 1 in 100 to 1 in 200 for French drains generally. Because the published figures differ, the right slope, depth and outlet for your lot are questions for a local contractor or designer.
When a curtain drain may make sense
- Water visibly runs toward the house from a slope, driveway or neighbor’s yard.
- The yard has an obvious downhill spot where the water can leave by gravity.
- Angi lists surface-level water, small volumes, sloped properties and clay soil as good fits for a curtain drain.
- You have already fixed the cheap things: gutters, downspout extensions and grading. See our guide to exterior drainage for basements.
When it is probably the wrong tool
- Water comes up through the floor or the floor-wall joint. That often points to groundwater pressure, and an interior drain with a sump pump is what Fine Homebuilding suggests in that case; see interior vs. exterior waterproofing.
- There is no place for the water to go. A curtain drain needs somewhere for the water to go by gravity. If the only outlet is uphill or too close to the house, the system has to pump the water, and that is a different design; see French drain vs. sump pump.
- The foundation has a crack that leaks. A drain in the yard does not seal a crack. See crack injection.
What it costs
Angi puts curtain drains at $10 to $25 per linear foot and interior French drains at $40 to $100 per linear foot. Our French drain cost guide shows other published ranges, which differ by source. These are published estimates, not quotes, and trenching difficulty, access, outlet and local labor all move the price. A curtain drain is usually cheaper than an interior system, but only if it addresses your actual water source.
Mistakes to avoid
- Choosing by name. Ask where the pipe sits and what water it is meant to catch.
- Skipping the filter fabric or using the wrong gravel, which invites clogging. Wikipedia names clogging as the main limitation of these drains.
- Tying downspouts into the drain pipe, which Fine Homebuilding advises against.
- Discharging onto a neighbor’s property or somewhere that causes new damage. Rules on discharge and permits vary locally, so check with your municipality first.
- Digging without calling 811 first to locate buried utilities, as Fine Homebuilding also reminds readers.
Questions to ask a contractor
- Where exactly will the drain run, how deep, and how will it be sloped?
- Where does the water leave, and is that allowed by local rules?
- What fabric and gravel will be used, and how is clogging prevented?
- Will gutter water be handled separately?
- How would we know if it stopped working, and what does the warranty cover?
Related guides
- Basement French drain cost
- Exterior drainage for basements
- French drain vs. sump pump
- Basement waterproofing cost calculator
How we put this guide together
This guide was drafted with AI assistance and then edited for the site against the public sources listed below. We are not engineers or contractors, and we have not installed or inspected any drain. Definitions and construction details come from the sources below; cost figures come from Angi. Because the sources use the terms differently, we have said so rather than pick one. If you spot an error, use the contact page and we will correct it.
