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Why Tar Coating Is Not the Best Basement Waterproofing Method

Homeowners are often surprised when their basement becomes humid even without broken pipes or leaky appliances. What many don’t realize is that concrete is porous.

While concrete walls seem sturdy, moisture can easily seep through them, especially if the basement hasn’t been waterproofed. Some homeowners add tar coating to their basement walls to solve this problem. Let’s explore the ins and outs of this solution to see if it’s actually effective.

What is Tar Coating?

Tar coating, also known as asphalt coating, is a waterproofing method that has been used for many years to keep basements dry. This compound is applied to the exterior walls of a foundation to create a moisture barrier.

Tar is a black and sticky substance that gives it excellent water-resistant properties. This makes it a popular option for basement waterproofing.

How is Tar Coating Applied?

Builders and contractors apply tar coating during the construction of a foundation. Here’s a deeper look at the process:

  1. Preparation: The foundation walls are thoroughly cleaned to remove any dirt, dust, or debris. This step is crucial because any impurities can reduce the effectiveness of the tar coating.
  2. Crack Repair: Any cracks or gaps in the foundation walls are sealed before applying the tar. This ensures a smooth surface and prevents water from seeping through these openings.
  3. Application: The tar coating is applied using brushes, rollers, or sprayers. Contractors typically use about three gallons of tar for every 100 square feet of wall surface. The application needs to be even and thorough to create a seamless barrier.
  4. Drying Time: Under optimal conditions of relative humidity and moderate temperatures, tar coating can dry within a day. However, in colder temperatures, the drying process can take up to a week.
  5. Finishing Touches: After the tar coating has dried, a latex primer is often applied to enhance adhesion and provide additional protection.

Is Tar Coating Effective?

The effectiveness of tar coating as a waterproofing solution for basements depends on several critical factors:


For tar coating to be effective, the foundation walls must be meticulously cleaned before application. Dirt, dust, and debris can prevent the tar from adhering properly to the wall surface, reducing its ability to form a seamless barrier. Proper cleaning ensures that the tar coating can bond effectively with the wall, maximizing its waterproofing properties.

Environmental Conditions

The success of tar coating is heavily influenced by the environmental conditions during application. Ideally, tar coating should be applied in moderate temperatures and low humidity.

High humidity can prolong the drying time and reduce the overall effectiveness of the coating. Conversely, very cold temperatures can cause the tar to become too stiff, making it difficult to apply evenly and potentially leading to cracks or gaps in the coating.

Manufacturer’s Guidelines

Adhering to the manufacturer’s guidelines and instructions is important during the application of tar coating. Each product has specific recommendations for application thickness, drying time, and additional steps that need to be followed to ensure the coating lasts. That’s why installation should only be handled by professionals.

Pros and Cons of Tar Coating


  • Seamless Barrier: Tar coating creates a continuous, unbroken layer that effectively prevents moisture from penetrating the foundation walls.
  • Durability: Once applied, tar coating can provide long-lasting protection against moisture. It remains effective for many years, offering peace of mind to homeowners.
  • High Tensile Strength: Tar coating is known for its high tensile strength, making it resistant to environmental factors such as hail, fire, and wind.


  • Toxic Fumes: One of the significant drawbacks of tar coating is the release of harmful fumes during application. These toxic fumes can cause skin irritation and respiratory problems.
  • Crack Sealing: Before applying tar coating, it is crucial to have any wall cracks professionally repaired. Simply covering them with tar will not solve the underlying issues and can still lead to water infiltration over time.

As you can see, tar coating might not be the best option anymore, especially because of it’s environmental and health impacts. Still, it does offer some benefits and can keep water out for a while.

Overall, you might want to consider new waterproofing methods, especially if you’re building a basement or if you’re noticing moisture in your existing basement. Consider the pros and cons of tar coating carefully!

Why Do Some Basement Have Tar Coating?

Concrete is porous and may develop wet stains like this.

When the concrete walls of a basement are built, water is used in the mixture. As the concrete cures, the water evaporates, leaving tiny pores in the walls. These pores allow water and humidity to leak inside during heavy rain, summer days, or periods of snowmelt.

This leads to issues such as mold growth, wet walls, or standing water in the basement. For this reason, some basements were built with tar coating to (hopefully) avoid these issues.

Other Ways to Waterproof Your Foundation

If your basement was built without tar coating, or if your tar coating isn’t keeping water out of your basement, there are modern options available. At AFS, we use these solutions to keep your basement dry:

  • Interior Drainage System: The drain is placed under the basement floor on top of the footer. It collects water that leaks in through basement walls and sends it to a sump pump.
  • Sump Pump: The sump pump receives water from the drainage system and pumps it away from your basement. It also stops water from leaking through the floor and flooding the basement.
  • Dehumidifier: The basement dehumidifier takes extra moisture out of the air. It helps stop mold growth, cuts down on musty smells, and makes the air healthier to breathe.
  • Wall Vapor Barrier: A wall vapor barrier stops moisture from getting into basement walls, helps prevent mold and damage, and seals basement walls from the inside.

Whether your basement is used for storage or as a living space, moisture is a problem. Water can damage your basement, compromise your home’s structural integrity, and affect your family’s health. Whether it’s with tar coating, other waterproofing solutions, or both—keeping your basement dry is important.

Contact AFS for Professional Basement Waterproofing

AFS crewmen posing in front of work truck.

Keeping your basement dry is essential for the health and safety of your home. While tar coating can be part of the solution, combining it with other waterproofing methods ensures the best protection against moisture.

To learn more about effective waterproofing solutions, contact AFS today. Schedule a free inspection, and our experts will assess your basement, identify any issues, and recommend the best waterproofing methods to keep your basement dry for years to come.

Tar Coating FAQs

Inspect your basement walls regularly for signs of moisture, such as dampness, mold growth, or peeling paint. If you notice any of these signs, it may indicate that the tar coating is no longer effective and needs to be reapplied or supplemented with other waterproofing methods.

Tar coating is derived from petroleum, making it less environmentally friendly compared to some other waterproofing options. The release of toxic fumes during application also raises environmental and health concerns.

Tar coating can last for many years, often providing effective waterproofing for over a decade if properly applied and maintained. The exact lifespan can vary based on environmental conditions and the quality of the application.


Ted Dryce

Ted Dryce

Content Writer

Ted is an SEO Content Writer who has been with Groundworks since 2021. He’s covered home repair topics ranging from crawl space encapsulation to regional soil conditions. When he’s not working, Ted is performing improv comedy and working on his own creative projects.

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