How to fix drainage problems
Most wet-basement quotes start with a $12,000 interior system. Most wet basements get fixed for $400 in downspout extensions and a half-day of regrading. The job of a good drainage pro is to diagnose the water path first, then sell you only the system you actually need.
Yard French drains run $30–$65/lf installed. Exterior foundation waterproofing runs $90–$250/lf of perimeter (excavation to footing + membrane + footing drain). Interior basement perimeter systems run $3,000–$15,000 for a typical home. Sump pump install runs $800–$2,500 depending on pit, discharge, and battery backup. Downspout extensions and regrading — the upstream fix — run $400–$2,500 and resolve most cases.
The biggest swing is which system the property actually needs. Interior perimeter systems are 5–10x the cost of grade and downspout work but get sold as the default. Soil type (clay vs. sandy loam), discharge distance to daylight, and excavation depth move the rest.
See what drives priceHow we price it
These are the factors that move a quote up or down. Knowing them helps you share the right context upfront so we can quote your specific situation accurately — and so you can compare bids on apples-to-apples scope.
This is the entire ballgame. A seep through a poured-concrete wall at floor level during heavy rain is usually a grade or downspout problem ($400–$2,500 fix). The same seep through a horizontal crack mid-wall, or weeping mortar joints in a fieldstone foundation, is a hydrostatic-pressure problem that needs an exterior membrane or interior perimeter system ($8,000–$25,000). Ask any pro to walk you through what they think is happening before they quote a system — the answer should be specific to your symptoms.
Yard French drain to intercept surface water: $30–$65/lf. Exterior foundation waterproofing (dig to footing, dimple membrane, new footing drain, backfill with stone): $90–$250/lf of perimeter. Interior perimeter system (jackhammer slab edge, drain tile to sump): $50–$120/lf of basement perimeter. The interior route is the easiest to install and the most heavily marketed, but it manages water that has already reached your foundation rather than keeping it away.
A French drain or sump is only as good as where the water goes. A property with daylight 30 ft from the house and a 4% grade is easy — solid 4" SDR-35 PVC, trench, done. A flat lot with no daylight needs a dry well ($800–$2,500) or a pump-up to street ($1,500–$4,000) plus the original system. If discharge falls within a wetlands buffer (200 ft in RI, 100 ft in MA), permitting adds $500–$3,000 and 4–12 weeks before excavation can start.
Yard French drains are 18–24" deep — a mini-excavator job. Exterior foundation waterproofing means digging to the footing (typically 7–9 ft for a full basement), which requires a full-size excavator, shoring on deep trenches, and respect for OSHA trench safety. Tight side yards where the machine cannot fit add hand-dig labor or hydrovac time. A walkout basement is the cheap case; a 9-ft full basement with a deck blocking the back wall is the expensive one.
Sandy loam drains itself and is forgiving. Heavy clay (common in eastern MA and parts of RI) holds water at the foundation no matter what you do upstream — interior systems and footing drains become more justified. A high seasonal water table (within 2–3 ft of the basement slab) means a sump pump is mandatory regardless of which exterior fix you pick. Ask the pro to verify the soil from a test hole before they quote a French drain — gravel layout changes by soil.
Most yard French drains under 24" deep do not require a building permit, but discharge into the public right-of-way usually does ($75–$300). Exterior foundation work near a property line or in a wetlands buffer triggers conservation commission review. Erosion control (silt fence, hay bales) is required on most excavations over a certain disturbance area and runs $200–$600. Dig Safe (811) tickets are free but mandatory — never skipped.
A $150 big-box sump pump and a $1,200 Zoeller cast-iron pump look identical on a quote line that just says "sump pump." The cast-iron unit lasts 10–15 years; the plastic unit lasts 2–4. Battery backup ($300–$800 installed) keeps the pump running through the power outages that often accompany the storms causing the flood — without it, you have an expensive system that fails exactly when it matters. Ask which pump model is being installed and whether backup is included.
What else might come up
Most projects touch more than one trade. Here's where this one usually overlaps with others — so you can plan ahead instead of scrambling.
Clogged gutters or undersized downspouts dump roof runoff at the foundation — the upstream cause of a large share of basement seepage calls. A good drainage pro will ask about gutter condition and downspout extensions before quoting a system; if they do not, you should.
Drainage manages water; it does not stabilize a moving wall. Horizontal cracks, displacement at the top of the wall, or block walls bowing inward need structural evaluation before the waterproofing membrane goes on. Sequence: structural fix first, drainage second.
Regrading the first 6 ft of perimeter to a 5% slope away from the foundation is the cheapest, highest-ROI drainage improvement available. Landscapers handle the lawn and bed reshape, drainage pros handle anything that requires a French drain or sub-grade pipe. Often a coordinated job.
Interior perimeter systems are a legitimate tool when external access is constrained or the foundation type rules out exterior fixes. They are the wrong tool when the cause is upstream and correctable. A second opinion is reasonable before committing to a $12,000+ interior system.
A sump pump needs a dedicated GFCI-protected 15A circuit and ideally a battery backup or water-powered backup. An electrician handles the dedicated circuit if one does not exist; the drainage pro handles the pit, pump, and discharge. Confirm the backup is included or scoped separately — the storm that fills the pit is often the one that takes out the power.
- Photos or short video of where water enters — wall location, floor seam, window well, slab crack
- When it happens — every heavy rain, only after snowmelt, year-round seepage, one-time event
- How long it has been going on and whether it is getting worse
- Age of the home, foundation type (poured concrete, block, fieldstone), and basement finish status
- Whether there is an existing sump pump and whether it runs during storms
- A sketch or photo of the yard showing slope direction, downspout discharge points, and where standing water collects
- Whether neighbors uphill have drainage systems or chronic water issues
- Distance to the nearest wetland, stream, pond, or shoreline (matters for outlet permitting)
- Recent landscaping or hardscape changes (new patio, deck, retaining wall, regrading)
- Any prior drainage or waterproofing work — what was installed, by whom, and what it cost
- Active water entering during or right after rain (vs. high-humidity condensation, which is a different fix)
- Horizontal cracks in foundation walls or visible bowing (structural concern, not just drainage)
- Sump pump running continuously or cycling on every few minutes during dry weather (high water table)
- Standing water in the yard 24+ hours after rain (saturated soil, possible compaction or clay layer)
- Outlet pipe or discharge near a wetland, stream, or shoreline (permitting required)
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