Brick Sealing and Waterproofing: Everything You Should Know

Written By Adam Paul - Waterproofing Expert

Bricks are a type of building material that is made from clay and burned in a furnace between 900–1100 °C. Burnt bricks are red in color, have higher porosity, and are more resistant to water. But bricks are not waterproof. Due to higher porosity, bricks can absorb water and remove over time. As a result, brick walls tend to seep water from the outside during the rainy season into the structure.

According to the ASTM, the recommended water absorption rate of the brick is 20%. Due to the higher water absorption of the brick, it can be damaged by brick spalling, mold and mildew growth on the brick, structural damages due to brick collapsing, and motor deterioration with the brick.

Brick walls are mainly of two types: old brick walls and new brick walls. These walls can be waterproofed by using a proper step by step guide. The most used brick sealers are Dominator sealer, Drylok Clear Masonry Waterproofer, and Redguard Brick Sealer.

You can protect a sealed brick by regular cleaning, reapplying the sealant, repairing damages, avoiding pressure washing, and protecting it from physical damage on the sealed wall. Sealed wall can be painted by applying the masonry primer. If the wall is not properly waterproof, water can come through the sealed brick wall.

What are the Bricks?

Bricks are a type of building material that is made of clay. Clay is burned to 900–1100 °C in a furnace to harden the bricks. Wet bricks can get wet easily, and their structure can collapse due to moisture, humidity, and water. However, burned bricks withstand water due to their higher water resistance. Due to the high porosity, the water absorption rate of the burned brick is higher, and when it is saturated with water, it tends to seep the water through the bricks.

Prolonged water seepage through the bricks tends to lose the structure and grow algae, fungi, and mosses on the surface over time. In order to prevent these problems, bricklayers should be protected from water.

Are Bricks Waterproof?

No, bricks are not waterproof material. Due to the higher porosity of the bricks, it absorb water at a higher rate. Once the brick is saturated with water, it seeps water through it. Prolonged water absorption through the brick can cause to fail the brick structure and tend to grow algae, fungi, and mosses on the surface over time.

How much Water Absorbed by the Bricks?

According to the ASTM (American Society for Testing and Materials), a brick should not absorb more than 20% of its weight in water. As an example, 1 Kg of brick can absorb a maximum 200g of water as per the ASTM standard.

Brick releases the absorbed water over time, and it can damage to the plaster, paint, tiles, insulations, and floor by making stain marks, seepage, and water leaking over time.

Due to the higher water absorption rate of the bricks, brick walls should be waterproof properly. Hence, exterior walls and bathroom wall waterproofing should be done to reduce the risk of damage.

What are the Water Damages of Bricks?

When the bricks are exposed to water, it tend to be damaged by the water. The most water damages on the bricks are spalling, mold and mildew growth, structural damage, and motor deterioration.

1. Brick spalling: Brick spalling occurs when water enters a brick, freezes, and then expands. This causes the brick to crack or flake.
2. Mold and mildew growth on the bricks' surface: Constantly damaged bricks can become a breeding ground for mold and mildew, which can be harmful to health.
3. Structural damages due to brick collapsing: Prolonged water exposure to brick can weaken the brick structure and lead to potential structural damage to the structure.
4. Motor deteriorations with brick: Prolonged water exposure to the brick can deteriorate the mortar. It compromises the stability of the structure.

How to Seal Bricks?

How to Seal Old Brick Walls?

You can seal old brick wall by following the below 5 steps.

1. Clean the older brick wall: First, you should clean the older brick wall by removing any dirt, mold, or mildew from the wall. You can do this using a brush and a mixture of warm water and mild detergent. For stubborn stains, you may need to use a pressure washer or a specialized brick cleaner.
2. Repair the damaged areas on the older brick wall: After the cleaning process, you should check the wall for any damaged bricks or mortar. You should repair these areas before you can apply the sealant.
3. Choose the right brick sealant: You should choose the right sealant for the brick walls. The selected brick sealant should be breathable (i.e., it allows moisture to escape from the brick), waterproof, and UV-resistant.
4. Apply the brick sealant: You should follow the manufacturer's instructions to apply the sealant on the brick wall. You can use a sprayer, roller, or brush to evenly coat the wall. You should cover all over the walls
5. Let dry the brick wall: After applying the sealant, you should let it to dry the sealant according to the manufacturer's instructions.

How to Seal New Brick Walls?

A newly constructed brick wall can be sealed by following the below step by step guide.

1. Clean the newly constructed brick wall: You should clean the newly constructed brick wall by using a pressure washer to remove any dust, and debris on the surface.
2. Let it dry the new brick wall: After the cleaning process, you should let it dry.
3. Apply brick sealer on the wall: You should apply brick sealer all over the wall using spray, roller, or brush.
4. Let the brick sealant cure: After applying the brick sealant, let it to dry as per the manufacturer guidelines.

What Can be Used for Brick Waterproofing?

You can use the below 3 brick sealers for waterproofing the brick walls. These products are the most used products for the brick sealing process.

Dominator Sealer

Dominator sealer is an acrylic based brick coating. Is is a moisture resistant, UV resistant, stain, scratch and rub resistant sealer It can be used for both interior and exterior sides of brick walls. It provides a natural look and good protection against moisture and stains.

It is available as 64Oz, 1-gallon, and 5 gallon containers. Dominator sealers can protect brick walls for more than 2 years. The 1 gallon will cover up to 250 sq. ft. - 400 sq. ft. per coat. The drying time of the Dominator sealer per coat is 1 hour. It is a low VOC with a very mild odor. 

Drylok Clear Masonry Waterproofer

Drylok clear masonry waterproofer can be used as a brick sealer. Drylok masonry sealer is a latex based clear and high gloss product. It can be applied by using a brush, roller or sprayer. It can be applied interior, exterior, vertical, horizontal, above or below grade walls.

One gallon of Drylok clear masonry waterproofer can cover 90-100 square feet on the surface. The drying time of the sealer is 2 hours per coat. It will withstand more than 5 hours on the surface. 

Redguard Brick Sealer

Redguard brick sealer is a water-based, breathable, water-repellent, stain-resistant, weather-resistant, moisture-resistant brick protection coating. But it is not a UV-resistant coating. It can be applied on both interior and exterior surfaces. It is non-toxic and safe for people, pet, and plants.

Redguard brick sealer can withstand 5 years on the surface. Using 1 gallon, you can apply 150 sq ft of surface area. You should apply 2 coats on the surface. The drying time of the coat is 30-60 mins. It should be applied between 40-90 Fahrenheit. 

How to Protect Sealed Bricks?

Sealed brick coating can be protected by following the methods below

1. Do regular cleaning the brick wall: You should wash the brick wall by using a mild detergent and water. Do not use harsh chemicals and hard brushes which cause to damage the sealant.
2. Reapply the sealant: The waterproofing efficiency of the brick wall is reduced over time. Hence you should reapply the sealant as per the manufacturer guidelines.
3. Repair damages: When you notice any cracks or damages in the bricks or the sealant, repair them as soon as possible to prevent water from seeping in and causing further damage.
4. Avoid pressure washing: You should avoid pressure washing the sealed brick wall to prevent damage by sealant by high pressure. You should use low pressure to clean the sealed brick wall.
5. Protect from physical damage: You should protect the bricks from physical damage, such as impact from heavy objects or scratching from sharp objects.

Can You Paint on Sealed Brick Walls?

Yes, you can use paint on sealed brick walls. First, you should use a masonry primer to cover the brick surface and let it dry. Then apply the desired paint on the brick surface. By applying a waterproof paint on the brick surface will add extra protection to the brick wall.

Why is Water Coming Through Sealed Brick Walls?

Water can come through sealed brick walls due to improper blocking of the cracks and holes in the brick. Brick sealants can seal the porous surface on the brick and it dos not able to cover the cracks and holes that are larger than 1-2mm. Hence, those cracks tend to leak the water inside the brick and continue the seepage.

Can I Seal Bricks Using Concrete?

No, You can't seal the bricks using concrete because concrete is not a waterproof material. Concrete is permeable, and it tends to leak water when saturated. In order to prevent this you should waterproof the concrete. Waterproof concrete does not allow the water to pass through the sealed layer and it is a successful solution for the laid bricks on the floor.