How much does it cost to waterproof a basement?

Interior waterproofing is cheaper than exterior waterproofing, and there are several methods a professional can use to sell your basement, including:

• Concrete sealer. Concrete sealing compound costs about $100 per gallon, and the labor costs of preparing and cleaning the floor and applying the sealer average between $3 and $12 per square foot.
• Silicate concrete sealer. Professional application of silicate concrete sealer averages between $3 and $9 per square foot. This liquid compound allows moisture to escape instead of trapping it in and leaves your walls looking the way they did before.
• Waterproof paint. Waterproof paint typically costs between $30 and $40 per gallon. This paint is made especially for basement walls and is designed to keep moisture away.

Waterproofing the exterior of your basement will cost between $9,000 and $15,000 for the average home. Most professionals will tell you that the best way to waterproof your basement is to fully waterproof the exterior, but it’s also the most expensive option.

This typically involves excavating the house to the foundation walls and installing a waterproof coating with drainage panels that lead to an exterior French drain at the bottom of your foundation.

Adding an interior drainage system — including a dehumidifier, sump pump and floor drain — costs between $700 and $2,600, on average. Depending on the region where you live, the additional load on utility bills to run a dehumidifier 24 hours a day could cost around $10 per month. A system like this will pull most moisture out of the air and direct the liquid into your drain and sump pump.

John Wernsdorfer of John W Property in Portsmouth, New Hampshire, says it's difficult to estimate waterproofing costs per square foot because each home or commercial property has such different needs. However, here are some cost examples for residential and commercial property waterproofing jobs done by his company:

Cost to waterproof 400-square-foot residential basement

• Total project cost: $500
• Cost of materials: $120
• Cost of labor: $380
• Completion time: One day of work

Overview of the project: “Water was leaking through the walls and floor in a newly purchased home after rainstorms. The water seeping in from underground turned out to be a function of bad drainage off the roof. We fixed the roof drainage and made minor gutter additions. We also installed a dehumidifier as a backup, stationed above the potential flood level to run 24 hours a day and drain automatically into the sump. The wetness was completely stopped.”

Cost to waterproof 600-square-foot residential basement

• Total project cost: $1,200
• Cost of materials: $400
• Cost of labor: $800
• Completion time: Two days of work

Overview of the project:  “Water from an underground shallow water table was seeping into the basement. We sealed the floor and walls as best as possible and slowed the seepage, but it’s not always possible to stop it completely. We then had a dehumidifier installed as a backup, stationed above the potential flood level to run 24 hours a day and drain automatically into the sump.”

Cost to waterproof 1,500-square-foot commercial basement

• Total project cost: $3,500
• Cost of materials: $2,000
• Cost of labor: $1,500
• Completion time: Three days of work

Overview of the project: “Water was leaking through the walls and floor in the furniture storage area of a new furniture store. Water was seeping in through draining cracks off the parking lot. We sealed the interior floor and walls, then filled the many cracks and tar holes in the parking lot draining water toward the basement. We also repaired a pooling water location near the basement entrance. This work slowed the seepage. We installed a dehumidifier as a backup, stationed above the potential flood level to run 24 hours a day and drain automatically into the sump. The water leakage was stopped almost entirely. Fully repairing the parking lot would have ended the problem, but the cost to repair and repave the lot was well above the client’s budget, so waterproofing provided an effective alternative.”

• Get multiple free estimates from professionals near you: Make sure you have a choice of materials and methods to be used, and you're getting a fair price.
• Confirm your pro’s qualifications: Make sure they are licensed, bonded and insured in your state.
• Read online reviews: Find out if previous customers were happy with the work and the work held up.
• Ask questions: Find out why the pro thinks their solution to your basement waterproofing needs is the best one.
• Confirm every detail: Ensure they guarantee and/or warranty the work and make sure you understand what is covered.

Waterproofing a basement is a costly undertaking, but preventing damage to your home’s foundation will save you money and agony in the long run. The best way to save money is to ask the contractor a lot of questions, research the materials and options available and hire someone whose solution you think makes the most sense for your basement and your budget.

Moisture in a basement can result from a variety of issues, such as poor drainage on the exterior of the home, groundwater seeping up and in from a water table below the foundation, condensation or actual leaks in the foundation.

Visible signs of a moisture problem include condensation forming on the walls, water pooling and/or ongoing musty odors. Leaks and cracks only get worse over time and can lead to mold in the home, as well as expensive damage to the foundation. Don’t put off waterproofing your basement if you see any signs of moisture.