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Tar Coating

Applying tar to the foundation walls in an inexpensive way of meeting the minimum standards of local building codes.

True, concrete foundation walls are durable and mostly maintenance-free. But they’re not water-resistant. Their porous nature means water vapor can seep through walls and floors. When there’s a downpour or melt-offs, you’re likely to experience water issues. These can lead to dampness, wood rot, mold growth, and other problems. 

Some homeowners use tar coating to stop dampness. Is this an effective deterrent against moisture? If not, what are your waterproofing options? We will take you through the steps of tar coating the foundation then look at the pros and cons of this damp proofing method. 

What Is Tar Coating? 

Tar coating is a common sealer that’s used for basement damp proofing around the country. Once the foundation is built, the bituminous compound is applied to the exterior walls, and a drainage pipe is set to deter water and moisture that’s threatening to get into your basement.  

Three gallons of tar is enough to cover 100 square feet. Tar takes four to eight hours to dry at 50% relative humidity and approximately 24 hours to set in. In cold and damp weather, tar can take up to seven days to dry. 

How to Apply Tar Coating to the Foundation 

Here’s how to coat below grade foundation walls with tar coating. 

  • Clean up your foundation wall to remove dirt and loose debris and sweep off any fine particles with a broom. 
  • Next, repair chips, holes, or cracks before coating then reinforce them with universal patching fabric. 
  • Apply the tar coating with an even stroke as you work from one end of the foundation wall to the other. 
  • Allow the coat to dry for 24-48 hours then apply latex primer once the tar adheres well on the foundation’s walls. It’s similar to wall paint and will soften the tar making it bleed through the primer. 

Make sure the coating extends one foot above the ground level. If you have to backfill the foundation’s perimeter, ensure the material is also one foot above the ground to protect the concrete. 

What Affects Tar Coating? 

Like any sealant, the effectiveness of tar application on the foundation depends on these factors: 

  • Surface cleanliness during tar application 
  • Adherence to the manufacturer’s guidelines and instructions 
  • Temperature, humidity, thickness at the time of application 
  • The presence of moisture or water on the exterior foundation wall 
  • A region’s climate 
  • Chemistry and composition of the fiber reinforcement 
  • Chemistry between the water and masonry wall, which can lead to efflorescence 

Note: Don’t apply the tar coating on a wet wall or if rain is imminent. 


Whether hot-mopped or self-adhesive, tar coatings are seamless, which helps stop dampness. Tar is also durable and has a high-tensile strength. What’s more is that this damp proofing material is rated against hail, fire, and wind. Once applied, it can hold up well for several years. 


During the tar application process, it can release toxic and harmful fumes. So, it’s best left to professionals. Exposure to harmful tar gases can also lead to skin and lung diseases. 

Note: Tar coating does not effectively seal cracks or other significant openings on the exterior walls. 

Waterproofing the Foundation 

Hot liquid tar coating has been the choice damp proofing material for concrete foundation walls. However, damp proofing the exterior foundation walls with tar coating alone won’t stop water from infiltrating your basement. You can retard water by implementing the following waterproofing measures: 

  • Seal cracks along the foundation 
  • Create a French drain to arrest water that pools around your home’s perimeter 
  • Install downspout extensions to direct water to the public drains or streets 
  • Grade the yard away from your home so water drains out 
  • Install gutters on the roof 

Many local contractors combine exterior drain pipes with tar coating to prevent water from building up around the home. As well as deterring moisture accumulation, these solutions stop water from infiltrating the basement walls. 

Blobbing tar on foundation walls won’t keep water out for the simple reason that it’s not flexible to seal any gaps or holes for long. Temperature variations will ultimately weaken its hold, meaning water will eventually infiltrate your basement. A more effective option would be to install waterproofing measures in your basement like an interior drainage system and a sump pump. 

If you’d like help with waterproofing your basement, contact JES Foundation Repair for a free waterproofing inspection and quote. Our experts will check the walls and recommend the next steps as well as solutions that will keep water out for good. 

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