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How To Waterproof a Basement (2024 Guide)

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Author Icon By This Old House Reviews Team Updated 08/10/2023

Basements provide extra storage or living space but are notorious for springing leaks and harboring moisture. The average cost to waterproof a basement is $3–$10 per square foot, but you can often save money by applying simple waterproofing products yourself. 

Excess dampness in a basement or crawl space can cause rot, mold, and water damage, potentially compromising your home’s comfort and structural integrity over time. We’ll explain how to do basic waterproofing yourself and when to do it. We’ll also help you identify the signs of more severe problems.

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Signs You Should Waterproof Your Basement

Some signs of basement water problems, such as standing water on the floor, are obvious. Others may be more subtle. Here’s what to look out for:
You see visible mold or mildew or smell musty odors.
A white, chalky substance called efflorescence appears on basement walls or floors.
The drywall or flooring is moldy, feels wet, or shows water stains.
Condensation develops on pipes, ducts, or windows.
Your water heater is getting rusty or creating puddles.

Prep Before Waterproofing Your Basement

Take the following steps to prepare your basement before beginning waterproofing.

Make Sure the Basement Is Dry

The basement should be as dry as possible before you begin. Standing water greatly increases the risk of electrical shock when using power tools. Even if the problem is minor, applying waterproofing products to a damp basement only traps moisture and risks more structural damage. You must pump out any standing water, remove damp or moldy porous materials, and use fans and dehumidifiers to dry the air as much as possible.

Clean and Inspect the Basement

Your dry basement can now be cleaned. If mold or mildew remains, clean basement floors and walls with antifungal cleaner or diluted bleach, but wear proper eye and respiratory protection. Efflorescence, a crystallized mineral residue left behind from evaporated water, can often be scrubbed or scraped away with a wire brush or paint scraper. Stubborn efflorescence may call for muriatic acid, which also requires respiratory protection. You may also need to remove old paint layers so the concrete sealers can adhere properly.

Remove anything with sustained water damage and attempt to locate the water’s source. Sometimes this will be obvious, such as damp streaks from wall cracks or puddles beneath leaky pipes. Other times, it may be unclear whether the problem is overly humid air or water seepage directly through uncracked concrete walls. 

You can easily test this by taping a 1-square-foot piece of aluminum foil to the wall and leaving it there for about 24 hours. If condensation develops on the outside, the problem is humid air from another water source within the basement. If condensation develops on the concrete-facing side, water is seeping through the walls.


Steps to follow

There are two types of basement waterproofing: interior and exterior. Exterior waterproofing for severe basement water problems usually involves excavation and regrading and is best done by professionals. For milder problems, you can apply many interior waterproofing products yourself. Here’s where to start.

Plug Holes and Cracks

Cracks tend to develop at mortar joints in cinder block walls but can appear anywhere. Basic crack repair requires a specific sealant. Larger cracks or gaps in a concrete floor or wall should be sealed with hydraulic cement, which can expand and contract during temperature changes along with the concrete. Silicate-based concrete sealers from Drylok and similar brands are also effective, but you must remove paint from any concrete surfaces before applying them. Cracks and holes of 1/4 inch or less can be filled with silicone caulk.

Reseal Windows, Doors, and Pipes

Areas around exterior windows and doors are notorious for springing leaks, so seal the area around them with silicone caulk or expanding foam. Pay special attention to window wells around egress windows since runoff can collect there. Apply sealant around anywhere that pipes or ducts penetrate foundation walls.

Apply a Waterproof Coating

Although waterproof paint alone won’t seal cracks, it’s a good final step to apply over hydraulic cement and other sealants. Masonry paint, epoxy paint, and acrolein elasticized paint are all highly water-resistant. Make sure to follow all manufacturer instructions, particularly if the paint contains hazardous chemicals when wet. Apply it on a day with no forecasted rain. You’ll usually need two to three thick coats for the job.

Install a Sump Pump

If standing water or flooding is a regular problem, install a sump pump to actively move water out and away from your home. There are two kinds of pumps: pedestal pumps, which have a motor that sits above the water line, and submersible pumps, which sit in the water itself. Pedestal pumps are less expensive and easier to install, but they’re also less powerful. Submersible pumps are more expensive and must usually rest in a specially lined pit in order to work, but they’re also more effective.

Check for Exterior Drainage

If water collects around the outside of your foundation, it can often make its way in through the basement. Your home’s gutters and downspouts should direct rainwater away from the foundation, but they must be in good repair and free of clogs to work. Periodically inspect your gutters to make sure they’re functioning properly, and have them cleaned twice per year. Additionally, ensure landscaping features that need watering, such as flower beds, are located far enough from your foundation to avoid problems.

Recognize Signs of Serious Problems

Small cracks and gaps can be patched relatively easily, but if you start noticing larger cracks or signs of sinking, you may be facing serious foundation problems. In areas where the ratio of groundwater to soil is high, hydrostatic pressure on your basement’s walls can eventually cause bowing or cracking. Note that horizontal foundation cracks are more indicative of severe problems than vertical cracks, but even large vertical cracks should be taken seriously. Additionally, if you notice uneven floors or cracking door frames in the other areas of your home, this can also indicate foundation problems. This needs to be inspected and addressed by a professional.


DIY vs. Professional Basement Waterproofing

Though the above solutions are do-it-yourself (DIY) friendly, there are times when you should call in a professional.

DIY Basement Waterproofing

Professional Basement Waterproofing

Most simple waterproofing options are well within homeowners’ skill sets. Sealants, epoxies, and waterproof paints are typically available at local hardware stores for less than $100, and you don’t need specialized tools to apply them. You can also take other steps around the house to ensure water drains away from your foundation. These and other basement waterproofing tips can help prevent future problems from developing.

Sometimes a wet basement, particularly one completely below grade in a high water table, can’t be fixed by plugging cracks and applying paint. If this is the case, you may need a more sophisticated interior or exterior drainage system, such as a French drain or drain tile system, which usually requires hiring a plumber. Additionally, foundation problems must be repaired by a  professional contractor. Although the cost of foundation repair is high, it’s necessary to protect your home.


How To Save on Basement Waterproofing

Here are some tips for lowering your basement waterproofing costs. 

  • For a basement that’s only damp, try sealing cracks yourself before calling in the pros.
  • Fully dry and clean your basement before installing waterproofing products or hiring professional waterproofers.
  • Purchase high-quality products when possible. These may cost more up-front but will likely save you money on repairs in the long run.
  • Take necessary prevention steps, such as ensuring your gutters are working properly and addressing potential leaks quickly.
  • If your goal is a finished basement, add waterproofing to your basement finishing costs to save on labor.
  • Have foundation cracks inspected and, if necessary, repaired as soon as possible to avoid more serious and expensive structural issues.

How To Hire a Pro

If your wet basement requires professional intervention, consider the following as you compare contractors.
Plumbers need a specific state-issued license, but other waterproofing contractors typically don’t. Regardless, anyone who does work on your home should be bonded and insured.
Look the company up on the Better Business Bureau website for its rating, accreditation status, and customer complaints.
Check out trustworthy customer review sites such as Trustpilot and Google Reviews.
Ask for references from previous customers.
Ask about interior and exterior waterproofing solutions and what’s available at various prices.
Get quotes from at least three local contractors to understand your area’s price range. Be suspicious about any quotes that are much higher or lower than others.

Our Conclusion

Waterproofing a basement isn’t glamorous, but protecting your home’s foundation is crucial. If you can identify leaks or other moisture sources, try sealing them yourself. If that doesn’t work, it may be time to call a professional waterproofing contractor to take more drastic measures.

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Typical Price Range: $2,000 – $7,500

FAQ About Waterproofing a Basement

What can I use to waterproof my basement?

Hydraulic cement and silicate concrete sealer are good choices for filling large cracks and gaps in a basement’s concrete walls and floors. Silicone caulk can fill small cracks and seal the seams around windows, door frames, pipes, and ducts. Finally, waterproof paint is a great final step to seal large, bare concrete areas.

Do I waterproof my basement from the inside or outside?

You can use either interior waterproofing, exterior waterproofing, or both. Interior waterproofing solutions are less expensive and disruptive but may be insufficient for serious water problems. Exterior waterproofing tends to cost more since contractors often need to dig to access your home’s foundation, but it often solves the problem for good when done correctly.

Is it worth it to waterproof a basement?

Basement waterproofing helps ensure your home’s structural stability and, thus, its resale value. Most homeowners find it’s well worth it to waterproof the basement.

How much does waterproofing a basement cost?

Fully waterproofing a basement of 1,000 square feet will generally cost between $3,000 and $10,000. Interior waterproofing solutions are usually at the low end of that spectrum, and exterior solutions, particularly in flood-prone areas, are at the high end.

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