How To Waterproof a Basement (2024 Guide)
Compare quotes from local foundation experts.
Join more than 6,755 people who have received a free, no-obligation quote in the last 30 days
Written by
Basements provide extra storage or living space but are notorious for springing leaks and harboring moisture. The average cost to waterproof a basement is $5–$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 handle basic waterproofing yourself and when to call in a professional.
* Cost data sourced from contractor estimates used by Angi.
Key Takeaways
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:
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. Even if the problem is minor, applying waterproofing products to a damp basement only traps moisture and risks more structural damage. Standing water also greatly increases the risk of electrical shock when using power tools.
Pump out any standing water, then use fans and dehumidifiers to dry the air as much as possible. Remove any porous materials, such as carpet or drywall, that are damp or moldy. Unlike hard surfaces, these materials typically cannot be disinfected and salvaged after water damage.
Clean and Inspect the Basement
Your dry basement can now be cleaned. Pay special attention to the following:
- Mold and mildew: If mold or mildew remains, clean the basement floors and walls with antifungal cleaner or diluted bleach. Be sure to wear the proper protective gear, including safety glasses and a respirator mask.
- Efflorescence: Efflorescence is a crystallized mineral residue left behind from evaporated water. Often, you can scrub or scrape this 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.
Identify the Moisture Source
Once your basement is clean and dry, 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.
How To Waterproof Your Basement
There are two types of basement waterproofing: interior and exterior. Waterproofing a basement from the outside usually involves excavation and regrading, which are best done by professionals. However, 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 in your basement floor or walls. Start by cleaning the cracks thoroughly with a wire brush to remove any loose debris or dust. Then select the right sealant based on the size of the crack.
Cracks and holes of 1/4 inch or less can be filled with silicone caulk. Larger cracks or gaps in a concrete floor or wall should be sealed with hydraulic cement, which can expand and contract with the concrete during temperature changes.
Silicate-based concrete sealers from Drylok and similar brands are also effective, but you must remove paint from any concrete surfaces before applying them.
Reseal Windows, Doors, and Pipes
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 the window wells around egress windows, since runoff can collect there. Apply sealant anywhere that pipes or ducts penetrate foundation walls. Check corners and the places where different siding materials meet the frame for gaps.
Apply a Waterproof Coating
Although waterproof paint alone won’t seal cracks, it provides an extra layer of protection over hydraulic cement and other sealants. Masonry paint, epoxy paint, and acrolein elasticized paint are all highly water-resistant.
Make sure the wall is clean, dry, and free of loose debris so the paint will stick, and apply it on a day with no forecasted rain. You’ll usually need two to three thick coats for the job. If the paint you choose contains hazardous chemicals, follow all manufacturer instructions and wear appropriate protective gear.
Install a Sump Pump
If your basement experiences regular flooding despite your best efforts to seal and waterproof, 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.
The best choice depends on the severity of your water issues and the layout of your basement. Pedestal pumps are less expensive and easier to install, but they’re also less powerful. Submersible pumps are more expensive and complex to install, but they’re also more effective.
Regularly test and maintain your sump pump so it works when you need it. Make sure the sump pump’s discharge pipe directs water away from the foundation to prevent it from simply recirculating.
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.
Ensure the ground slopes away from your foundation to direct water away from the house. You might need to add soil for this in certain places. Pay special attention to low spots in the yard where water might pool, and keep landscaping features that require water, such as flower beds, well away from the foundation.
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 can cause basement walls to bow inward or crack. Horizontal foundation cracks are more indicative of severe problems than vertical cracks, but vertical cracks wider than 1/8 inch should be taken seriously.
Signs of foundation problems might also appear throughout your home. Look for uneven floors or cracks around door frames in upper levels. If you notice any of these red flags, have a qualified structural engineer or foundation expert assess the situation and recommend appropriate repairs.
Check out the video below for more DIY-friendly wet basement solutions. Expert Richard Trethewey discusses the different sources of moisture in a basement and how to address each one.
Can You Waterproof Your Basement Yourself?
Though the above solutions are do-it-yourself (DIY) friendly, there are times when you should call in a professional.
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, such as regrading your lawn, cleaning gutters, and extending downspouts. These and other basement waterproofing tips can help prevent future problems from developing.
While DIY options are often effective in addressing minor leaks and moisture, they often don’t solve the underlying cause of the problem. However, they can provide a temporary solution while you investigate more permanent fixes or save for professional help.
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.
You should also hire a professional to assess large, sudden, or persistent problems and handle any major repairs. For instance:
- Suspected structural damage
- Severe water intrusion
- Extensive mold growth
- Chronic, unsolved leaks
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.
- DIY fixes: If your basement is only damp, try sealing minor cracks yourself before calling in the pros.
- Prep work: Thoroughly dry and clean your basement before installing waterproofing products or hiring professional waterproofers.
- Smart product choices: Compare prices from different stores and invest in high-quality products when possible. Though they cost more upfront, they can save you money in the long run.
- Preventive maintenance: Regularly clean your gutters, check downspout extensions, and ensure the ground slopes away from your home.
- Bundling projects: If your goal is a finished basement, add waterproofing to your basement finishing costs to save on labor.
- Prompt repairs: Have foundation cracks inspected and professionally repaired as soon as possible to avoid more serious and expensive structural issues.
How To Hire a Pro
When DIY solutions aren’t enough, here’s how to find a reliable basement waterproofing contractor:
Should You Waterproof Your Basement Yourself?
Waterproofing your basement helps prevent moisture from penetrating the foundation and compromising the structural integrity of your entire home. Even small leaks can lead to bigger issues over time, so taking timely action is key.
If you can identify leaks or other moisture sources, try sealing them yourself. If that doesn’t work, or if you discover more significant issues, it may be time to call a professional waterproofing contractor. A small investment in waterproofing now can save you from costly repairs and protect the overall value of your home.
FAQs About Waterproofing a Basement
What can I use to waterproof my basement?
For minor leaks and moisture, you can use hydraulic cement, silicate concrete sealant, and silicone caulk to fill cracks and gaps. You can apply these products yourself, followed by waterproof paint. Larger problems may call for exterior drainage improvements or professional foundation repairs.
Do I waterproof my basement from the inside or outside?
You can waterproof your basement from the inside, the outside, 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 excavate around your home’s foundation, but it often solves the problem for good when done correctly.
Is it worth it to waterproof a basement?
Yes, waterproofing a basement is worth it. Basement waterproofing helps protect your home’s structural integrity and, thus, its resale value. It can also prevent mold growth, water damage, and foundation issues—all of which can be expensive to fix.
How much does waterproofing a basement cost?
Fully waterproofing a 1,000-square-foot basement will generally cost between $5,000 and $10,000. Interior waterproofing solutions are usually at the low end of that spectrum, while exterior solutions, particularly in flood-prone areas, are at the high end.
To share feedback or ask a question about this article, send a note to our Reviews Team at reviews@thisoldhousereviews.com.
