Published 2026 French drain cost ranges
These figures are broad published industry ranges — not fixed Islip pricing and not a quote for your property. HomeGuide currently lists roughly $10–$35 per linear foot for many yard or curtain drains, about $30–$90 per foot for deep exterior perimeter drains, and about $40–$85 per foot for interior basement systems. HomeAdvisor reports an overall average project around $9,250, with a very broad professional-installation range because project types differ so much.
Why we do not publish a fake “Islip starting price”: a drainage quote should be based on the actual water source, trench depth and length, outlet or storage method, access, utilities, restoration, and site conditions. A national per-foot number can be useful for planning, but it is not a substitute for seeing the property.
What changes the price of a French drain in Islip?
Length and depth
More trenching means more excavation, stone, pipe, fabric, labor, hauling, and restoration. Deep foundation work is materially different from a shallow yard interceptor.
Where the water goes
A drain still needs a safe destination. A simple gravity outlet is different from a project that requires a dry well, catch basin, sump or another storage/discharge strategy.
Machine access
Open side-yard access can reduce labor. Tight gates, fences, patios, decks, utilities or areas that require hand digging can increase it.
Existing landscaping
Sod, planting beds, pavers, walkways, irrigation and finished hardscape may need protection or restoration after trenching.
Water source
Surface runoff, roof runoff and groundwater are different problems. Installing a long French drain when grading or downspout drainage is the real issue can waste money.
Soil and groundwater conditions
Long Island conditions vary by parcel. Soil infiltration, saturation and groundwater depth affect whether a proposed outlet or dry well is practical.
Yard French drain vs. exterior foundation drain vs. interior system
The phrase “French drain” gets used for several different systems, which is a major reason online pricing looks inconsistent.
| Type | Typical purpose | Why cost differs |
|---|---|---|
| Yard / curtain drain | Intercept saturated soil across a lawn or side yard | Often shallower and easier to access |
| Exterior foundation drain | Manage water alongside a foundation | Deeper excavation and greater restoration |
| Interior perimeter drain | Manage water entering at the basement perimeter | Concrete cutting, interior work and sump/discharge requirements |
Before paying for a French drain, make sure a French drain is actually the fix
If the puddle starts directly below a downspout, underground downspout drainage may deserve attention first. If the yard visibly pitches toward the house, grading or a swale may be part of the answer. If the problem is a surface low spot, a catch basin or dry-well system may be more appropriate. A French drain is most useful when water moving through saturated soil is the problem being intercepted.
Town requirements and underground utilities can affect the project
Project requirements depend on the scope and property. Before excavation, the contractor should review applicable Town requirements and utility-markout responsibilities. Our Town of Islip drainage permit guide links directly to Town Engineering resources and New York 811 information.
How to get a more useful estimate
- • Photograph or video the water while it is actually happening.
- • Note how long the area remains wet after rain stops.
- • Show nearby downspouts, patios, driveways and foundation walls.
- • Mention whether the basement gets damp or takes on water at the same time.
- • Identify obvious access restrictions such as narrow gates, decks or finished hardscape.
Related Islip drainage guides
Frequently Asked Questions
French drain pricing questions
How much does a French drain cost in Islip, NY?
There is no reliable one-price-fits-all Islip figure because cost changes with drain type, length, depth, access, excavation, discharge method, landscaping restoration, and site conditions. Published national guides show wide ranges, so a property-specific estimate is the best way to price an Islip project.
Is an exterior French drain more expensive than a yard French drain?
Usually. Exterior foundation work can require deeper excavation, more difficult access, waterproofing or foundation-related work, and substantially more restoration than a shallow yard or curtain drain.
Why do French drain estimates vary so much?
Two drains with the same length can have very different costs if one is shallow with easy machine access and a nearby outlet while the other requires hand excavation, deeper trenching, a dry well, utility coordination, or extensive landscape restoration.
Can I get a free French drain estimate in Islip?
Yes. Describe the drainage problem, property location, and how long water remains after rain to request a free, no-obligation drainage estimate.