Tar coating the foundation walls is great for maintenance, but it also has a weakness. Over time, it is susceptible to water damage due to its porous nature. This is especially true in areas that have high rainfall, snowfall, or humidity. As new concrete dries, the water inside the concrete evaporates, leaving behind a network of capillary pores. It is these pores that make the concrete porous. Over time, water can move through the concrete, causing other issues such as mold and damage to wooden structures like beams and floors.
What happens if you don’t fix a wet foundation? As the water seeps into the concrete, it can erode the foundation and this can lead to cracking. This is a much bigger problem and will cost a lot more to fix, so ensuring your home’s foundation is waterproof is a wise investment.
A common way to deal with this issue is to apply a coating of tar to the concrete and take other measures to move water away from the house foundation using gutters and drains.
What Is Tar Coating?
Tar is often derived from materials that contain a lot of carbon, such as wood, oil, or coal. It can be used as a sealant for concrete walls. About three gallons of tar can cover around 100 square feet of wall. Once painted onto the outer wall the tar will dry. How long it takes to dry can depend on the humidity and temperature. Drying times vary from about one day to about one week. Once it has dried, it forms a waterproof surface on the concrete.
How to Apply Tar Coating to the Foundation
Applying a coat of tar to a foundation wall requires several steps:
- Make sure the wall is clean and free of dust. Remove any fine particles with a broom. If the wall surface is not clean and dry the tar may not adhere properly to the wall’s surface. This will limit the effectiveness and lifespan of the coating.
- Any chips, holes, or cracks in the wall’s surface need to be repaired. The tar by itself will not seal larger cracks or holes.
- Apply the tar coating with even strokes, working from one end of the foundation wall to the other. It is important to get a coat of even thickness.
- Give the tar coating time to dry, at least 24 hours. Once dry, you can apply a latex primer. Make sure the coating extends one foot above the ground level.
What Affects Tar Coating?
The effectiveness and lifespan of a tar application on the foundation depends on many factors, including:
- How well the coating sticks to the concrete, make sure the concrete is clean and dry before starting to apply the tar.
- Make sure to follow the manufacturer’s guidelines.
- It is best to apply the tar to wall and let it dry before it rains next, check the weather forecast before starting the job.
- The chemistry between the water and masonry wall, which can lead to efflorescence.
When applied correctly, tar forms a strong, durable, and waterproof layer that will protect concrete walls against dampness for years. It is relatively inexpensive and when applied by professionals, it can be done quickly and safely.
Tar can release toxic fumes while it is being applied, these fumes can cause skin and lung problems, so this is a job best left to professionals. Compared to penetrating sealants, tar does not allow the concrete to breathe and sits on the surface of the concrete. It can therefore degrade over time and will need to be replaced.
Waterproofing the Foundation
By itself, tar will not fully guarantee that the foundation is 100% waterproof. Several other actions can help. You want to prevent water pooling around your home’s perimeter. You can do this by building a French drain and making sure your yard and any lawn are graded away from your home. Install gutters on the roof and make sure they take rainwater away from the foundation by installing downspout extensions.
More effective solutions include interior waterproofing measures such as an interior drainage system, sump pump, vapor barrier, and dehumidifier.
When combined correctly, these measures will help take most water away from your home and deal with any dampness that remains.
You can also insulate basement pipes with foam. This will help reduce condensation and dampness, which in turn will help prevent the musty smell that some old basements can have.