How To Waterproof a Basement From the Outside
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Keeping your basement dry helps prevent water damage, mold growth, and serious foundation problems. If you notice musty odors, condensation, discolored drywall, or puddles in your basement, it’s time to take action. While some methods involve waterproofing from the interior basement walls and floors, exterior waterproofing may be necessary when more severe moisture problems arise.
Our guide explains how different basement waterproofing methods work and why waterproofing is important. We also provide step-by-step instructions for waterproofing a basement from the outside.
What Causes Basement Water Problems?
A wet basement can result from a number of issues, from leaky pipes or clogged drains to poor drainage of precipitation runoff around your house and yard.
- Hydrostatic pressure: When it rains heavily or snow melts rapidly, the soil around your foundation becomes saturated with water. This water will push against your basement walls and floor, literally trying to force its way inside. It may gain entrance through cracks in the foundation, window wells, or gaps where the floor meets the walls.
- Poor drainage and grading: If the ground around your home slopes towards the foundation instead of away, water will pool against the basement rather than running off. Hydrostatic pressure builds in the oversaturated soil, and the water looks for a way inside.
- Faulty gutters and downspouts: Clogged gutters will overflow, dumping water directly beside your foundation. Leaky gutters and downspouts that are too short do the same thing—they don’t take water far enough away. This leads to oversaturated soil.
- Cracks in the foundation: Foundation cracks can happen over time due to settling, extreme temperatures, or poor construction practices. These cracks provide a direct pathway for water to seep through, especially when there’s pressure from outside.
- Interior humidity: Some basement moisture comes from inside your house. Humid air condenses on cool basement walls and surfaces. Activities like showering, laundry, and cooking can contribute to this problem.
- Plumbing issues: Leaky pipes, burst connections, or clogged drains can steadily release water, saturating the floor or seeping into walls. Even seemingly minor leaks can eventually lead to larger-scale moisture problems in your basement.
- Groundwater: In areas with a high water table, groundwater can seep into the basement through the foundation. This occurs when the water table level rises above the level of the basement floor. This water intrusion can lead to damp floors and walls, cracks, and even standing water in the basement.
- Water vapor: Water vapor in the soil can pass through porous basement materials like concrete, even without visible leaks. This process occurs regardless of the water table level, driven by differences in vapor pressure. Humid soil has higher pressure, pushing moisture toward the drier basement air.
Water seeping through the walls or floor of your basement can weaken the entire foundation over time. This is of particular concern in areas with high water tables or lots of precipitation.
Risks and Consequences of Basement Water Problems
A damp basement isn’t just uncomfortable—it can cause serious structural damage to your entire home. Here are some of the consequences of neglecting basement water issues:
- Structural damage: Over time, hydrostatic pressure and water infiltration can cause your foundation walls to bow or crack. This can lead to severe structural instability, potentially compromising the safety of your entire home.
- Interior damage: High humidity and condensation in your basement can lead to rotting wood, damaged drywall, and peeling paint. Additionally, dampness promotes the growth of mold and mildew, further deteriorating the basement environment.
- Pest infestations: Damp basements can attract pests like termites and cockroaches. These insects thrive in moist environments and can cause further damage by burrowing through wood or spreading bacteria.
- Health and safety hazards: The mold and mildew growing in a damp basement release spores into the air that can trigger respiratory problems or exacerbate allergies. The moisture also creates electrical hazards, increasing the risk of shocks or fires.
- Reduced home value: Basement water problems can significantly decrease your home’s value. Potential buyers are often wary of the cost of repairs, health concerns associated with mold, and the potential for future issues.
For more information about the different sources of dampness in a basement and how to address them, check out the video below. Plumbing expert Richard Trethewey explores wet basement solutions that direct water away from your foundation, provide a vapor barrier, and control the humidity in your basement.
What Are the Benefits of Basement Waterproofing?
Here are some ways waterproofing your basement walls can benefit you:
- Preserve structural integrity: Waterproofing helps maintain the stability and safety of your entire house for years to come.
- Avoid expensive repairs: Basement waterproofing prevents water damage, potentially saving you thousands of dollars on foundation repair costs.
- Enjoy a healthier home: A dry basement means no mold or mildew growth, which significantly improves indoor air quality.
- Preserve structural integrity: Waterproofing helps maintain the stability and safety of your entire house for years to come.
- Boost property value: A dry, usable basement is a major selling point that attracts buyers and commands a higher sale price.
- Prevent pest infestations: Waterproofing creates a less hospitable environment for pests and a stronger barrier against them.
- Gain usable space: Waterproofing can turn a damp, uninviting basement into more livable square footage.
Waterproofing your basement is a wise investment that yields long-term benefits. It protects your home and health and adds to its overall comfort and value.
Types of Basement Waterproofing
Basement waterproofing solutions fall into two main types: interior and exterior.
Interior basement waterproofing involves several techniques to stop water from entering the space. You can repair small cracks in concrete or cinder block walls with hydraulic cement or sealant. You can also fill gaps around doors, windows, ducts, and pipes with polyurethane sealer.
Complete the sealing of basement walls with several layers of waterproof paint. More serious water seepage problems require installing a waterproof membrane called a vapor barrier between the concrete and any finishing materials.
Waterproofing contractors can install an interior drainage system to address pooling water. This drainage system might include a French drain system, which consists of drain tiles surrounded by gravel into which water can flow. Installing a sump pump can move the water away from the foundation.
Exterior foundation waterproofing is more expensive and disruptive, but it’s the most effective option. One method is to improve drainage by upgrading gutters and extending downspouts to ensure runoff is directed away from the house.
Other methods include regrading your yard so water runs away from the foundation or installing window well drains or covers to prevent water from leaking into basement windows. French drains are also useful for exterior drainage, allowing an escape route for excess water.
If groundwater is a problem, you may need to expose the exterior foundation and apply a cementitious coating or waterproofing membrane to the foundation walls. This rubberized asphalt membrane keeps all water out and is often the most effective solution. However, it’s also the most expensive option because you’ll need to excavate and then backfill the area around the foundation.
Interior waterproofing methods are relatively inexpensive and useful for mild to moderate water problems, but they still allow water to penetrate foundation walls. Large foundation cracks and other major issues will require waterproofing the exterior walls and addressing the root cause of the problem.
How To Waterproof a Basement From the Outside: Step-by-Step Guide
Here’s how to execute your exterior waterproofing project:
Check gutters and downspouts to ensure they’re unclogged and in good condition. Remove blockages, and fix any holes.
Ensure downspouts empty at least 5 feet away from the foundation, installing downspout extensions if necessary. Alternatively, install rain barrels to catch runoff and use the runoff for irrigation or car washing.
Move shrubs, flowers, or living landscaping features that require frequent watering away from the home’s exterior walls.
Regrade the soil that extends around the home’s perimeter so the yard slopes away from the walls.
Install French drains along the base of this slope by digging trenches and installing perforated pipe. Cover pipes with gravel and loose topsoil to allow water to filter down. Extend pipes to a dedicated runoff trench or a sump pump pit.
Contact a professional waterproofing contractor about methods that require excavation if these solutions are insufficient.
For more basement waterproofing tips, check out the video below with general contractor Tom Silva:
How To Maintain Your Exterior Basement Waterproofing System
Once you have a system in place, it’s important to maintain it to keep water draining properly.
- Check your sump pump regularly to make sure it’s operating properly. Have a backup battery in case of a power outage during a heavy rainstorm.
- Have a professional inspect any large or vertical foundation cracks as soon as possible. These can be signs of serious damage, and catching them early may prevent more expensive repairs later.
- Ensure that in-ground drainage systems haven’t become clogged or filled with soil.
- Have gutters cleaned at least once per year and potentially more frequently if your yard has a lot of trees. Gutter guards will keep some debris out, but they don’t allow you to avoid cleaning gutters completely.
DIY vs. Professional Basement Waterproofing
While homeowners can install some waterproofing solutions themselves, others require professional contractors.
Many basic interior waterproofing methods, such as keeping gutters clean and performing minor yard regrading projects, are DIY-friendly. Motivated DIYers can install a basic exterior drainage system, though the process may require renting excavation equipment.
Doing this work yourself will save on labor costs, but ensure you know what tools and permits you need. For example, you should always call 811 before you dig so you don’t disturb buried utility lines.
More extensive drainage systems and waterproofing of exterior foundation walls are tasks best left to the professionals. Relying on experienced professionals to perform foundation work protects your investment in your home because your foundation supports the house’s structural integrity.
Many waterproofing materials require professional installation to maintain their warranty. Pros will know what permits to get and how to adapt to unexpected complications.
How To Hire a Pro
Here’s how to tackle hiring a professional contractor for exterior basement waterproofing:
Our Conclusion
For stubborn or recurring basement water problems, exterior waterproofing is often the best solution. While it may have a higher upfront cost, it addresses the root cause by keeping water out of your foundation entirely. This offers long-term protection and less need for ongoing maintenance compared to interior fixes. We recommend consulting with professional waterproofing contractors to get a better sense of your options.
FAQ About Exterior Basement Waterproofing
How much does it cost to waterproof a basement from the outside?
Exterior basement waterproofing costs vary substantially by the waterproofing method. For example, installing an exterior French drain will cost $15–$35 per linear foot, and yard regrading typically costs $900–$3,000*.
*Cost data in sourced from Angi.
How long does it take to waterproof a basement from the outside?
Exterior basement waterproofing can take anywhere from a day to a week, depending on the basement size and waterproofing method.
How do I know if my basement needs waterproofing?
Here are some signs your basement needs waterproofing:
- Bowed or cracked foundation walls
- Condensation on pipes or windows
- Efflorescence on concrete
- Mold or mildew
- Musty odors
- Visible flooding or standing water
Can you waterproof a basement from the inside?
Yes, you can waterproof a basement from the inside. This is often less expensive and disruptive than exterior waterproofing, but it may not fix severe water problems.
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