Basement Waterproofing Cost in St. Louis, MO (2026)
The price of keeping a basement dry in St. Louis, MO depends on how many walls take on water, what the foundation is made of and which fixes the house actually needs. This guide sets out published ranges with their sources and years, the details that push a total up or down, and what a sound written estimate should include.
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Costs at a Glance
| Cost row | Figure | Source (year) |
|---|---|---|
| Typical basement waterproofing project | about $3,000 to $10,000 (average about $5,000) | Fixr national (2026) |
| Interior perimeter drain, per linear foot | $40 to $120 | Fixr national (2026) |
| Sump pump installation | $600 to $2,500 | Fixr national (2026) |
| Epoxy crack injection, per crack | $250 to $1,000 | Fixr national (2026) |
| Waterproof paint or sealant, per sq ft | $1 to $8 | Fixr national (2026) |
Each row is a national figure from Fixr's 2026 guide, not a tally of St. Louis jobs. HomeGuide's 2026 national guide puts full projects higher, at about $6,000 to $18,000. Treat both as rough bookends. Your real figure arrives on paper, from a contractor who has looked at the walls in person.
Most jobs combine rows. Take a basement about 150 feet around that leaks along half its length, which works out to 75 feet of interior drain. Add a new or first sump pump and one injected crack, and the national rates come to roughly $3,900 to $12,500. The cost calculator runs the same math with your answers.
Two sewer items sit outside the table and the calculator. For water rising through a floor drain, look first at the Metropolitan St. Louis Sewer District's Sewer Backup Prevention Program, which may pay for a backflow valve for customers whose backups come from MSD's system. According to HomeGuide, as cited by HomeServe (2026), a privately paid backflow valve often costs a few hundred dollars up to about $1,000. Sewer lateral repairs usually run $1,000 to $8,000 (City of Kirkwood's lateral program brochure), and the City and many County cities run lateral programs of their own.
Details That Change the Total
Most of what shifts a price is visible before any digging starts:
- How far the drain runs. Drain pipe is charged by the foot, which is why fixing a single damp wall runs well below circling the whole basement.
- What the walls are made of. Census survey data puts the median City home's construction at 1938, with roughly 58% standing by 1939, so brick and limestone rubble foundations turn up often, and they let water through differently than poured concrete or block.
- Shared basements. In a brick two-family or four-family flat, one basement may serve several households, which can stretch the drain run and add people to coordinate.
- The pump setup. Cutting a first pit costs more than swapping a pump in an existing basin, and a battery backup or alarm adds to it.
- How many cracks. Injection is priced per crack, so three cracks run about three times one.
- Digging outside. Opening up the yard to reach a wall's outer face means heavier equipment and more hours than an inside trench. This guide found no sourced figure for it, so it lists none.
- Permits and trades. Drain connections and backflow valves need a licensed plumber or drainlayer, and the City requires building permits for foundation repair and underpinning. The contractor confirms which permits apply.
- Finished space. Paneling, carpet or a packed storage corner may have to come out before work begins.
Getting an Accurate Number
A real price only comes from someone who has stood in your basement. Two or three written estimates are easier to compare when each one covers the same ground:
- Local licensing. At a City address, the contractor's City business license, which the License Collector can confirm at (314) 622-4528. In St. Louis County, whatever your municipality requires, plus a County-licensed master plumber or drainlayer for drain work.
- Insurance papers. Certificates showing liability insurance and workers' comp.
- Walls and footage. Which walls get drain, and how many feet in all.
- Pump details. Make, model, any backup or alarm, and where the discharge pipe ends.
- Permit responsibility. Who pulls each permit, confirmed with the City's Building Division at (314) 622-3313 or your municipality.
- Payment terms. A schedule tied to progress. The Missouri Attorney General advises against paying in full up front or in cash.
- Warranty terms. Its length, what it covers and whether it transfers to a buyer.
A local address and references help too. Pressure to sign the same day is a good reason to slow down.
Coverage Questions
Sewer backups are often missing from a standard homeowners policy unless the owner bought a separate endorsement for them. Slow seepage is a common exclusion as well. Look through your policy and put the question to your insurer or agent before work begins, so you know whether to budget for the whole bill. This site plays no part in insurance and can't say what any policy covers.
Water coming up a floor drain is more likely a sewer backup than seepage. Report it to MSD's 24-hour line at (314) 768-6260. If an overloaded MSD sewer caused it, MSD may reimburse some losses, up to $3,000, when reported within 30 days. The lateral from the house to the sewer main belongs to the owner, which is where the lateral programs come in.
Get Your Own Estimate
For a ballpark built on your own measurements, try the cost calculator. When you want a firm number, the form sends your details to one independent local contractor, who visits the house and hands you a written price. You are never charged and never handed anything for using it. Contractors may buy advertising here, but this site does not bid on or carry out basement work. Filling in the form is the whole first step.