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What Is Tar Coating?: Exterior Basement Waterproofing Method

tar coating on foundation wall

It is a common misconception that thick concrete foundation walls will keep your basement safe from the elements, especially water. Unfortunately, what a lot of homeowners don’t realize is that concrete is porous, which means it is full of tiny openings. 

Water from the soil can enter the basement through concrete walls and cause problems. At first, you will notice that your basement is getting moist. Over time, those pores will widen, and water will start making its way in. During rainstorms or when large volumes of snow begin to melt, you will experience problems in your basement if you don’t waterproof the walls. Increased moisture levels in this area of the home can lead to wood rot, mold growth, and various other issues.

If you plan to use your basement as storage or you want to finish it and use it as a guest bedroom, a home gym, or an entertainment area, you should protect it from moisture. Several methods are used for this purpose and a tar coating can be one of them. 

Tar coatings have been used for a long time by contractors. However, would a tar coating be the best solution for your basement? How effective is tar and should it be used together with other waterproofing measures? Read on to learn more as we discuss the pros and cons of using tar coating and provide you with all the details you need to make an informed decision.

What Is a Tar Coating?

Using tar coating to protect the basement against moisture is not something new. It has been practiced for decades all around the world. When builders are constructing a building, they apply this compound to the exterior foundation walls to keep moisture from infiltrating them. Afterward, they install a drainage system to direct water and moisture away from the home. How much tar do they use to cover the walls? Well, usually about three gallons of tar are sufficient for 100 square feet of foundation walls. While tar can dry in one day, it will need up to a week if it is very cold or damp outside.

How to Apply Tar Coating to the Foundation

You should never apply tar coating on your own. Instead, call building contractors that serve the Michigan area and have them apply this coating to your foundation. 

When contractors arrive at your home, they will first clean the whole foundation wall to remove any dirt. They will then inspect the wall to see whether there are any cracks and if so, they will repair them before moving on with the project. Next, they will apply tar coating with even strokes, spreading it evenly and making sure that it extends one foot above the ground level. After the coating is dry, which can take a day or two depending on the weather conditions, contractors will apply latex primer. 

What Affects Tar Coating?

When applying a tar coating, contractors need to pay attention to several things. Some factors can impact the effectiveness of tar coating, so they must be taken into consideration. The surface of the wall must be completely clean, otherwise, the coating won’t keep the moisture out. In addition, the manufacturer’s guidelines and instructions have to be followed step by step. Another factor that can impact tar coating and lower its effectiveness is temperature. The presence of moisture on the exterior foundation wall also plays an important part.

Pros and Cons of Tar Coatings


This coating is seamless. If it is used correctly, it can stop dampness. In addition, it is durable and has high tensile strength, so you can be at ease knowing that it will keep your basement safe from moisture issues for years.


You should never apply tar coating by yourself. During the application process, tar releases toxic fumes which can severely harm you. This is why it is better to leave this task to skilled contractors and steer clear of DIY projects.

To make sure that water or moisture won’t infiltrate your basement, it is important to fix any existing cracks beforehand. Applying a layer of tar over the cracks won’t keep the moisture out. Experienced contractors will know to seal any cracks and large openings before applying waterproofing measures.

Waterproofing the Foundation

Tar coatings have been used for decades to protect foundation walls from moisture. However, this can not be the only waterproofing measure you take if you want to keep your basement dry and clean. If you want to finish your basement and convert it into a living space, you will need to also use other waterproofing solutions.  

To fix the cracks and other openings in your foundation walls, you will need to seal them or have foundation repair solutions installed if the cracks are significant. If water is constantly pooling next to your home’s perimeter, you will need to solve this problem first. Your contractors can install a French drain, as well as downspout extensions to direct groundwater away from your home. In addition, you can make sure that your yard has a positive grade. This means that water runoff won’t move toward your home, but instead away from it. If you have gutters, make sure that they are not clogged. Otherwise, roof water will spill over the gutters and end up on the ground around your home.

A lot of contractors in Michigan combine tar coating with exterior drainpipes. These pipes can prevent water from building up around your home and infiltrating your foundation walls. Would you like to waterproof your foundation walls and keep your basement safe from water damage? If so, contact your local contractors at FSM and schedule a free inspection and quote. One of our inspectors will provide a thorough assessment, determine if any problems need to be quickly solved, and recommend waterproofing solutions that will best suit your home.

We help protect everything you love, starting with your home’s foundation.

Tar Coating FAQs

Common symptoms include jamming doors and windows, sloping floors, and various forms of cracking in the home’s interior and exterior. 

Rainwater can increase hydrostatic pressure on basement walls and floors, seeping through existing cracks or imperfections.

Costs vary based on basement dimensions and requisite materials. We offer free inspections, transparent pricing, and financing options to suit your budget.

Leah Leitow

Leah Leitow

Content Writer

Leah is a Content Writer for Groundworks with nearly ten years of experience working in the foundation repair industry. Her experience ranges from working with homeowners to find the right solution to training inspectors and staff. In her background as a Michigan journalist, she gained invaluable insight into people's lives throughout our state. Leah lives in metro Detroit with her husband and two sons.

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