Moisture belongs on the outside and not in your basement or crawl space
As a homeowner, it’s important to take preventative measures to avoid potential moisture issues in your basement or crawl space. Doing so can avoid mold growth, poor indoor air quality, damage to building materials, and even severe structural damage to your home. Knowing how to waterproof a foundation is a critical first step, whether you’re DIYing a solution or hiring a pro. In this guide, we’ll explain what foundation waterproofing is and how to do it in your home.
Foundation waterproofing can include a variety of materials and techniques that create a barrier to prevent water from interacting with your foundation and remove it if it leaks through. These include exterior solutions like French drains, gutter systems, soil gradation, and damp proofing. There are also interior solutions, like a sump pump, waterproofing paint, and foundation crack sealing.
The foundation waterproofing process can look different from one home to another, and there are many methods you can use, such as using sealants on the interior or exterior or adding French drains near the property. In all cases, you should have a basement waterproofing company develop a waterproofing plan to ensure your home is adequately protected.
The average cost to waterproof a foundation is around $5,000, but you could pay anywhere from $1,000 to $15,000, depending on the specific waterproofing techniques your professional recommends. Simple setups like soil gradation and a gutter system will likely cost closer to the lower end of that range, while a more extensive system that includes a French drain and a sump pump inside will push toward the upper end.
Water and foundations do not mix well. Excess moisture and pooling water lead to a number of problems, such as mold and mildew growth and structural damage, which is why foundation waterproofing is critically important. There are other reasons in addition to preventing water intrusion, including the following:
Maintains structural integrity: When the soil around your foundation is dry, it won’t go through cycles of expansion and contraction, and it won’t put undue stress on your foundation that could otherwise cause structural damage.
Reduces mold and mildew: Moisture wicking through your foundation promotes mold and mildew growth under your home, which not only damages your building materials but also decreases indoor air quality and poses health risks to anyone living there.
Protects valuable belongings: Waterproofing protects your personal belongings stored in basements or crawl spaces, preventing potential water damage from damaging or destroying them.
Decreases energy costs: Waterproofing improves your home’s energy efficiency, reducing heating and cooling costs by preventing moisture from affecting the inside temperatures.
Minimizes future repair costs: Investing in foundation waterproofing up front might save on future repair costs by preventing water-related damages and associated foundation repairs.
Complies with building codes: There are some areas where local building codes require foundation waterproofing for greater longevity.
There are several methods for foundation waterproofing, and you should have a professional develop a customized system for your home that will treat the underlying problem, safeguard your foundation, and fit into your budget. Their methods ultimately depend on your home’s location, soil integrity, and foundation structure. These methods either take place on the interior or exterior of the home, and you may need a combination of several of these options.
"Waterproofing is crucial for basements to prevent water intrusion, mold growth, and structural damage. Interior waterproofing methods like sealants and vapor barriers help control moisture levels but don't address the root cause. Exterior waterproofing, such as waterproof coatings and French drainage systems, are often more effective in preventing water from entering the basement."
— Tim O'Shea, The Build Pros
There are quite a few ways to waterproof your foundation from the inside. Interior waterproofing is usually considered a reactive solution because it deals with moisture and water after they have already entered your space.
Waterproof sealants applied to the interior foundation walls and floor can create a protective barrier against moisture. These sealants, such as silicate, can be effective in preventing minor water seepage and helping to keep the humidity levels lower in a basement.
This method involves applying a waterproofing membrane to the interior foundation walls, which creates a barrier that prevents water from seeping through the basement floor. It then directs the water toward a foundation drainage system. There are liquid-applied membrane (LAM) options or sheet applied, both of which can be a DIY project, but it’s usually best to hire a professional.
You can inject epoxy resin into any cracks in your interior foundation, which can create a watertight seal. You can use an epoxy repair kit to fill in any cracks or gaps for your basement waterproofing, but most homeowners hire a professional to complete the work, as cracks that require an epoxy injection could indicate structural damage and the need for additional repairs from an expert.
A sump pump is a bucket that sits under the concrete slab in a crawl space or basement, with the top sitting flush with the floor. Since the bucket is the lowest point in the space under your home, pooling water will naturally flow into the bucket, where the pump redirects it, usually to a drain pipe, for safe disposal. Sump pumps are a reactive measure that will remove standing water rather than preventing water from entering your home.
A floor drain is similar to a sump pump in that it sits below the slab and collects pooling water, but instead of a bucket, it’s a trench that travels around the perimeter of your crawl space or basement. These drains then direct water to a sump pump for proper disposal.
Like sump pumps, floor drains are a reactive solution to remove water that has already gotten into your crawl space or basement. As such, they will not prevent moisture issues in your basement, mold growth, or structural damage caused by soil expansion and contraction around your home.
Crawl space encapsulation involves sealing the crawl space with a heavy-duty vapor barrier. If water seeps in through the concrete, it gets stuck behind the vapor barrier rather than filling the space under your home and affecting your indoor air quality in the floors above.
Lastly, you can install a dehumidifier in your under-home area to deal with moisture problems. This is another reactive solution, but it’s effective for reducing the risk of mold growth and indoor humidity, which, in turn, improves indoor air quality and your home’s overall efficiency and comfort.
There are also several options for waterproofing your foundation from the outside. These solutions are more proactive because they deal with water and moisture before entering your under-home area and sometimes before even interacting with your foundation. Since these address moisture issues in the soil surrounding your home, they can potentially reduce the risk of structural damage and water and moisture problems.
A gutter system is one of the most valuable pieces of foundation waterproofing you can install, and in many cases, it can get rid of your moisture problems entirely. Gutters and downspouts collect excess runoff from your roof and route it to an area away from your foundation for safe disposal. Extending your home’s downspouts away from the foundation with downspout extenders helps channel rainwater further from the house, which reduces the risk of water seepage even further.
A French drain is an underground drainage system consisting of a perforated pipe about two feet underground and covered by gravel. Rainwater and snowmelt will drop through the gravel and into the pipe, which routes the water away from your foundation for safe disposal.
French drains are more expensive than gutter systems because they require excavation, but they’re another excellent waterproofing option that can eliminate your moisture problem entirely.
A footing drain is similar to a French drain, but rather than sitting a foot or two underground, it sits around your foundation footings, which can sink more than nine feet under the surface, depending on your location and the depth of the frost line. Footing drains pull water away from your footings to prevent structural damage caused by soils shifting around the deeper portions of concrete.
Footing drains can require deep excavation, which makes them an expensive and intrusive solution. Contractors often install these during construction rather than retroactively.
Proper grading around the foundation is another effective method for exterior waterproofing. It ensures the soil slopes away from your home, which naturally pulls water away from your foundation. This is an affordable and DIY-able option, but it isn’t really a standalone solution.
Cementitious waterproofing is a topical application that consists of cement and a waterproofing agent, like a synthetic emulsion polymer. It creates a moisture barrier when applied because the particles expand against one another when in the presence of moisture, creating a water-tight seal. This waterproofing method can get expensive because it involves excavating around your entire foundation.
Dampproofing is either a rubber membrane or a liquid waterproofing material that a contractor can install on the exterior walls of your foundation. It prevents water in the soil around your home from soaking through the concrete, but it won’t protect from pressure from expanding soil. As such, it won’t prevent structural damage.
Foundation waterproofing can be an all-in-one solution to water and moisture problems with your foundation and can stave off structural problems. However, you should follow the tips below to ensure you get a system that suits your property, solves your issue, and keeps you and your family safe.
Hire a professional. Designing a foundation waterproofing system that treats your underlying problem effectively and permanently is a job for an expert. Even if you plan on DIYing the installation, hire a pro to design your system for you to make sure you’re getting a comprehensive fix that will last for years to come.
Prioritize proactive solutions. Unless your area floods, prioritizing proactive solutions—usually on the exterior of your home—is usually a better idea. Doing so will help avoid structural damage to your home and can deliver many of the same results as reactive solutions with additional benefits.
Consider your location. Taking your location into consideration is key when waterproofing your foundation. If your area sees flooding commonly, proactive solutions like a French drain might be a waste of money and a sump pump might suit you better. There’s no singular best way to waterproof a foundation—your solution should adapt to your location and climate.
Combine interior and exterior options. Combining interior and exterior waterproofing methods is a great way to eliminate moisture and water issues at the source. Have safeguards in place, too, in case water gets inside.
Take safety precautions if you DIY. If you DIY any of your waterproofing options, make sure to keep yourself safe. Excavation, mold removal, and working with sealants and other waterproofing materials containing volatile organic compounds (VOCs) can all be dangerous. Wear safety equipment and take the proper precautions.
If you’re comfortable DIYing your foundation waterproofing, you stand to save close to $5,000, on average, as the labor for waterproofing tends to make up the bulk of the cost. However, you should, at the very least, hire a professional to design your system for you. Doing so will prevent unnecessary measures that don’t suit your specific property, ultimately saving you time and money.
With that being said, we only recommend considering DIYing some of the simpler waterproofing methods, like grading your soil away from your home, installing downspout extenders, and applying a sealant over thin foundation cracks that you know don’t suggest structural problems.
For most waterproofing solutions, we suggest hiring a professional. Of course, you will pay more for the labor, but hiring a pro to install your basement waterproofing system is worth it to keep yourself safe and ensure you get a system backed by a warranty.
"Safety is key when working around foundations, crawlspaces, and basements. Always wear protective gear like gloves, masks, and goggles, and ensure proper ventilation. Minor tasks like filling small cracks and basic inspections can be DIY projects, but leave structural repairs, extensive waterproofing, and significant drainage work to the pros."
— Tim O'Shea, The Build Pros
Both interior and exterior waterproofing offer significant advantages to the foundation of your home and prevent excess moisture from seeping in, but exterior waterproofing is usually considered a better option. This is because exterior waterproofing methods prevent water and moisture from entering your basement at all, while interior methods involve removing water and moisture after they’ve already gotten inside. Exterior waterproofing can also help avoid structural damage by preventing soil around your home from putting excess pressure on your foundation.
Although not as common as with basements or crawl spaces, you can add waterproofing to a slab foundation. The most popular waterproofing options for slab foundations include footing drains—usually as a part of the initial construction—and gutter systems. In some areas, a builder might also recommend installing a moisture-resistant barrier beneath your slab during construction to prevent moisture from wicking up into your living space.
How long your foundation waterproofing system lasts depends on the methods you use and how severe the underlying problem is that you’re treating. If you just have a minor moisture problem and install gutters, downspouts, and a dehumidifier under your home, the system could last for decades without needing additional work. In most cases, you can expect a professionally installed system to last for 10 to 20 years without additional maintenance. Many experts will offer a waterproofing warranty, so pay attention to the coverage your system includes when hiring a basement waterproofing professional.
