French Drain Cost Calculator

A French drain typically runs $25 to $65 per linear foot installed, so a common 100-foot run lands roughly $2,500 to $6,500, with larger or more complex projects scaling from there. The drain type is the biggest driver: a yard or surface drain is cheapest (~$25/ft) because it's shallow, an exterior foundation perimeter drain is mid-range (~$50/ft) for its deeper trench alongside the footing, and an interior basement drain is the most expensive (~$65/ft) because it means breaking and re-pouring the slab and usually adding a sump pump. Trench depth and soil then adjust the rate, and add-ons like a sump pump, catch basin, outlet, and restoration stack on top. Enter your length, type, depth, and soil in the calculator above for a localized estimate.

A French drain is a gravel-filled trench, dug at a slight downhill slope, lined with landscape fabric and fitted with a perforated pipe, then covered with more gravel and sometimes soil or sod. Water in the surrounding ground takes the path of least resistance — it seeps through the gravel, enters the pipe through its holes, and flows by gravity to a discharge point well away from the problem area (a low spot in the yard, a storm drain, a dry well, or a daylight outlet on a slope). It's named for Henry French, a 19th-century farmer who popularized the design, not for France. The keys to a working drain are proper slope (about an inch of fall per 10 feet), quality gravel and fabric to keep soil from clogging the pipe, and a good discharge point — the calculator prices installation for yard, exterior, and interior versions.

They target different problems and install very differently. An exterior (foundation perimeter) drain is dug outside, alongside the footing — a deep trench down to footing level with pipe and gravel — to intercept groundwater before it reaches and pressures the foundation, keeping the basement or crawl space dry from the outside. It addresses the source but requires major excavation around the house (disturbing landscaping, walkways, or decks), so it's labor-intensive and mid-range (~$50/ft). An interior drain is installed inside the basement — a channel is cut into the slab around the perimeter, pipe and gravel go in, and it collects water coming up through or under the slab and routes it to a sump pit and pump. It's the priciest type (~$65/ft) because of the concrete work and sump, but it's often the practical choice for a finished home since it doesn't require digging up the whole yard.

Only if the drain can't discharge by gravity. A French drain flows downhill on its own, so if your lot has enough slope, it can simply 'daylight' at a lower spot or tie into a storm drain or dry well with no pump — common for yard drains and many exterior drains on sloped lots. A sump pump becomes necessary when there's nowhere lower for the water to go: most notably interior basement drains, where the floor sits below the surrounding ground and collected water must be lifted up and out. There, the drain feeds a sump pit and the pump switches on automatically to push water away from the house. A flat lot with an exterior drain that can't reach a lower outlet may also need one. The sump pump and basin is about $1,200 here; for reliability, many owners add a battery backup.

Because most of a French drain's cost is the digging. Soil is a big factor: standard, easy-to-dig soil is the baseline, dense clay is heavier, stickier, and slower (adding about 15%), and rocky, gravelly, or hardpan ground is the worst — sometimes needing special equipment or rock breaking — adding around 35% or more. Tree roots, hidden utilities, or buried obstacles slow it further. Depth multiplies the work too: a shallow surface trench moves little soil and costs less (about −15%), while a deep, footing-level trench moves far more material, may need shoring for safety, and takes much longer to dig and backfill (about +25%), plus more gravel. Poor access — a backyard a machine can't reach — can force hand-digging, which is dramatically more labor. The calculator adjusts the per-foot rate for both depth and soil.

A simple, shallow yard drain is a feasible DIY project if you're willing to do the digging, nail the slope (about an inch of fall per 10 feet), use fabric and proper gravel so the pipe won't clog, and have a valid downhill discharge point — and you call 811 first to have utilities marked. Where DIY gets risky is exterior foundation and interior basement drains: exterior drains need deep excavation against the foundation (dangerous trenches that can undermine the footing if done wrong), and interior drains require cutting and re-pouring concrete plus integrating a sump pump. Mistakes there can worsen water problems, damage the foundation, or simply fail to keep the basement dry — improper slope, thin gravel, or a bad outlet are the classic DIY failures. Given that water intrusion causes expensive foundation and mold damage, foundation and basement drains are usually worth a pro.

A well-installed French drain typically lasts 30 to 40 years, sometimes longer, but lifespan hinges on installation quality and a little upkeep. The most common failure is clogging — over time, fine soil, silt, and roots can migrate into the gravel and pipe and restrict flow. Good installation extends life dramatically: wrapping the pipe and lining the trench with quality filter fabric keeps soil out, clean properly-sized gravel preserves flow, and correct slope keeps water moving instead of depositing sediment. Maintenance is modest — periodically clear the discharge outlet, keep aggressive tree roots away from the line, and flush or snake the pipe if flow drops. Adding a catch basin or cleanouts makes future cleaning far easier, which is why they're popular add-ons. Interior drains also need the sump pump tested and replaced every 7–10 years.

That's the make-or-break detail, and it depends on your lot. The best outlet is gravity to a lower spot: the drain can 'daylight' — open to the surface — on a downhill slope, often with a pop-up emitter that lifts when water flows. Other gravity options are tying into a storm drain (where local code allows) or discharging into a dry well, a gravel-filled pit that lets water percolate into the ground. When there's no lower point — a flat lot or a below-grade basement — the water goes to a sump pit and is pumped out through a discharge line. A catch basin (a surface grate) can also feed the drain where runoff collects. Wherever it exits, the discharge must be far enough from the house that water doesn't just circle back, and clear of neighbors' property. The calculator includes daylight outlet, catch basin, and sump options.

Often, yes — a French drain is one of the most effective fixes for a chronically wet basement, but which type depends on where the water is coming in. If groundwater is pressuring the foundation from outside, an exterior perimeter drain intercepts it before it reaches the wall, addressing the source — though it means excavating around the house. If water is already getting in through the slab or the floor-wall joint, an interior drain collects it and sends it to a sump pump. Many basement problems are also helped enormously by cheaper fixes first: extending downspouts, regrading soil to slope away from the house, and clearing gutters. A drainage or waterproofing pro should diagnose the water's path before you commit, since the wrong drain in the wrong place won't solve it. The calculator prices interior, exterior, and yard drains so you can compare.

Most French drain installs take from one day to about a week. A short, simple yard drain in easy soil with machine access is often a single day, sometimes two. An exterior foundation perimeter drain takes longer — frequently a few days to a week — because the trench is deeper, runs around part or all of the house, and landscaping or hardscaping may need removal and restoration. An interior basement drain also runs several days to a week: the crew breaks up the slab perimeter, digs the channel, installs pipe and gravel, sets the sump pit and pump, and re-pours the concrete, which then has to cure. Long runs, hard digging, poor access, wet weather, and the extent of restoration all stretch the timeline. Your contractor can give a firm schedule after assessing length, type, depth, soil, and access.