Basement waterproofing
A damp or leaking basement can come from a few different places, and each one needs a different fix. Here's what interior drains, sump pumps, crack repair and exterior waterproofing actually cost, how to tell which one your house needs, and how to hire a contractor who finds the cause before quoting the cure.
Water gets into basements in a handful of ways: through cracks in the wall or floor, up through the joint where the wall meets the floor, over the top of the foundation when the ground outside slopes the wrong way, or as plain humidity condensing on cool concrete. The right fix depends on which one you have.
That is why two waterproofing quotes for the same house can look nothing alike. One company proposes an interior drain and sump pump, another wants to dig outside, a third says regrade the yard and extend the downspouts. A good contractor explains what is causing the water and why their system addresses it.
This page covers what basement waterproofing costs nationally, the difference between interior and exterior systems, when a sump pump is needed, how to compare quotes priced per linear foot, and what to ask before signing. City pages linked below carry local pricing and licensing for your market.
The work
01
The contractor cuts a channel in the basement floor along the walls, lays perforated pipe in gravel, and slopes it to a sump pit. Water that comes through the wall or up at the wall-floor joint is collected and pumped out. It manages water rather than stopping it at the wall, and it is the most common fix for an existing finished or unfinished basement.
02
A pit and pump at the low point of the basement that removes water collected by the drain system. Quotes should name the pump, its horsepower and switch type, where it discharges outside, and whether a battery or water-powered backup is included.
03
The soil is dug out down to the footing, the wall is cleaned, and a waterproof membrane or coating goes on the outside face, usually with new footing drains. It stops water at the source but costs the most, and access around decks, driveways and landscaping drives the price.
04
Polyurethane or epoxy is injected into a poured-concrete wall crack to seal it from the inside. It works well on isolated leaking cracks. A crack that is wide, growing, or offset may point to a structural problem that should be looked at by a foundation contractor or engineer first.
05
Coatings and plastic wall liners that control dampness and direct seepage down into a drain. Paint-on sealers alone rarely stop active leaks; they are best for minor dampness or as part of a larger system.
06
Regrading soil to slope away from the house, extending downspouts, and adding surface or French drains. These are often the cheapest fixes and are worth checking before paying for a full system.
07
A properly sized basement dehumidifier handles humidity and condensation that no drain system will fix. Often added alongside a drain and sump system in finished basements.
08
Leaking basement windows are often a window well problem: no drain at the bottom, no cover, or a well that fills during heavy rain. Fixes include new drains, covers and resealing the window.
Plan the budget
National planning ranges. Basement size, wall type, how much of the floor has to be cut, and how far the water has to be pumped all move these numbers. Ask for perimeter work priced per linear foot so quotes compare cleanly. Your city page carries local pricing.
| Scope | Planning range | What changes it |
|---|---|---|
| Interior drain tile with sump (full perimeter) | $5,000 – $15,000 | Most common whole-basement fix |
| Interior drain tile, per linear foot | $40 – $100 per linear foot | Includes cutting and re-pouring the floor |
| Sump pump installation (new pit) | $1,000 – $3,000 | Pump, pit, discharge line |
| Sump pump replacement (existing pit) | $500 – $1,500 | Name the pump model in writing |
| Battery backup sump pump | $800 – $2,000 | Added to a primary pump |
| Crack injection, per crack | $400 – $1,000 | Isolated poured-wall cracks |
| Exterior excavation and membrane | $100 – $300 per linear foot | Highest cost, stops water at the wall |
| Interior wall sealer or vapor barrier | $3 – $10 per square foot | Dampness control, not active leaks |
| Regrading and downspout extensions | $500 – $3,000 | Often worth trying first |
The cause of the water: surface drainage, wall cracks, hydrostatic pressure from below, or humidity each need a different fix.
Interior vs. exterior approach, and how much of the perimeter needs work.
Linear feet of wall, and whether a finished basement has drywall, flooring or built-ins that must come out and go back.
Wall type: poured concrete, concrete block, stone or brick behave differently and take different repairs.
Sump pump grade, switch type, backup power, and how far the discharge line runs.
Exterior access: decks, patios, driveways and mature landscaping make digging slower and more expensive.
Permits for excavation, drainage or electrical work, which should appear as a line item.
Know the signs
One small damp spot after a big storm may be a downspout problem. Several of these together usually mean water is getting in regularly.
Standing water or puddles on the floor after rain or snowmelt.
Damp or dark patches on walls that come and go with the weather.
White, chalky deposits (efflorescence) on concrete or block walls.
A musty smell, mold or mildew on stored items or the bottom of drywall.
Water stains or a visible tide line along the base of the walls.
Leaking or seeping wall cracks, especially near windows or pipe penetrations.
Peeling paint, bubbling sealer, or rusted metal near the floor.
A sump pump that runs constantly, or a pit that overflows in storms.
No pressure
You don't need to diagnose the job before you ask for help. Tell Henry what you see and compare up to three local basement waterproofing companies.
Get matched with a proHire with confidence
The best predictor of a good waterproofing job is a contractor who tells you, in writing, where the water is coming from and why their fix addresses it.
Ask the contractor to explain the cause of the water before recommending a system, and put it in the quote.
Get perimeter work priced per linear foot, with the total footage measured and stated.
Name the sump pump brand and model, the switch type, the discharge location and any backup in writing.
Ask whether cheaper exterior fixes (grading, downspout extensions) were checked first.
For wall cracks, ask whether the crack looks structural and whether an engineer or foundation contractor should see it.
Get the warranty terms in writing: what is covered, for how long, whether it transfers, and what voids it.
Confirm who restores the floor, drywall and finishes the job disturbs, and who hauls away debris.
Verify the contractor license or home-improvement registration your state requires, plus liability insurance.
Confirm whether a permit applies in your city and who pulls it.
Get at least two or three written quotes, especially when the recommended systems differ.
A full system recommended without anyone explaining what is causing the water.
A lump-sum price with no linear footage or itemized parts.
Scare tactics about mold or structural collapse to force a same-day decision.
Paint-on sealer sold as the fix for active leaks.
A pump with no brand or model named, or no discharge plan.
A lifetime warranty with no written terms, or one that only covers the parts.
Large deposits well beyond what is needed to schedule the work.
Related work
If you're seeing wide or growing cracks, bowing walls, or sticking doors along with the water, a foundation contractor should look at it too.
Questions homeowners ask
It depends on the fix. Sealing a single leaking crack can be under $1,000, a new sump pump typically runs $1,000 to $3,000, a full interior perimeter drain with sump commonly lands between $5,000 and $15,000, and exterior excavation is the most expensive at roughly $100 to $300 per linear foot.
Exterior waterproofing stops water before it reaches the wall but costs much more and disturbs the yard. Interior drain systems manage water that gets in and route it to a sump pump; they cost less and work year-round. Many homes are well served by interior systems, but the right choice depends on what is causing the water.
If water collects under or around the basement floor, yes — an interior drain needs a pump to remove what it collects. Homes with only surface drainage problems may not need one once grading and downspouts are fixed.
Rarely. Waterproof paints and sealers can reduce minor dampness, but water under pressure pushes through or behind them. They are not a substitute for fixing drainage or installing a drain system.
Not always. Most wet basements are drainage problems. But wide, growing, stair-step or offset cracks, bowing walls, or doors that stick can signal structural movement, and those should be evaluated by a foundation contractor or engineer.
A sump pump or crack injection is usually a one-day job. A full interior perimeter drain often takes two to four days, and exterior excavation can take a week or more depending on access and weather.
It varies by city. Excavation, new drainage connections, sump discharge and electrical work for pumps commonly need permits in some jurisdictions. Ask the contractor who pulls the permit and confirm with your local building office.
A documented, warrantied system can make a home easier to sell, and buyers and inspectors look for signs of past water. Keep the paperwork, and ask whether the warranty transfers to the next owner.
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Local market guides
Each city page covers local labor pricing, weather, permits, licensing, neighborhoods and the contractors Henry can match in that market.
City guides are being written now. Henry can still match you with a local pro.
Tell Henry what you need. We’ll send your project to no more than three local pros — and you decide whether any of them earns your business.
Sources: U.S. EPA — Mold and moisture in homes · FEMA — Protect your home from flooding · FTC — Hiring a Contractor · International Code Council — residential code
The Henry Standard
Call back. Keep appointments. And if something changes, communicate it.
Cause of the water, linear footage, pump model and warranty terms in writing — no vague lump sum.
Complete every item on the scope, restore the floor, and clean up before calling it finished.
Nothing revolutionary. Just the way we believe doing business should still be done.
