How to Waterproof Exterior Walls – What Coating to Use?

How to Waterproof Exterior Walls

It may not seem intuitive at first, but moisture can penetrate the masonry that makes up your outer walls to affect the inner walls of your home.

Over time, exterior walls that are exposed to rain and humidity can seep through the bricks until they reach the wood and drywall of the interior.

In especially humid places like the southeastern part of the US, exterior walls that take longer to dry out will present danger of moisture damage along with mold or mildew for the interior.

To prevent such damage to the interior of your home, you will need to take the following steps to ensure that the exterior is properly sealed from moisture. 

Steps to Waterproof Your Exterior Walls

Plastering the walls is a traditional way to protect your home exteriors.

It’s a reliable product that can not only protect exterior walls from moisture but also improves the aesthetic value as well.  

But the plaster is often not enough in many cases, which is why you will need to waterproof the walls well.

To start with the waterproofing process, you can follow these steps…

Step 1 – Inspection

The first step is to conduct an inspection of the exterior walls to find any faults.

This means you are looking for obvious sources of moisture penetration or creation.

From cracks in the bricks to condensation forming inside the walls to a pipe that is leaking, addressing the faults first will prevent moisture damage even after you waterproof the exterior.

Once that is completed, you are ready for the next step.

Step 2 – Gutter Cleaning

Gutters that are clogged not only cause the water to flow down the exterior walls they also retain water that may be absorbed by the roof or fascia boards of the home.

By cleaning your gutters at least twice a year, you can prevent water buildup that may add to the damage being created.

This also helps control the growth of mold as well.

Step 3 – Choose the Right Waterproofing Product

Different waterproofing products are made for different materials.

To properly seal an exterior wall, you should choose a waterproofing coating that matches the material.

For brick and concrete, for example, using a concrete waterproof coating will do the job.

Or you can use a silicate-based concrete sealer which will create a waterproof coating on the surface of bricks and concrete.

However, this type of sealer can only be used on walls that are not painted or previously sealed.

If you want to paint the walls, then waterproof paint that is similar to acrylic will work nicely.

You will need to select the right breathable formula to allow any moisture trapped under the paint to dry out.

This type of paint can be used on walls that have been painted.

Step 4 – Prepare the Walls for Waterproofing

Whatever product you choose, it is important to repair any damage to the surface of the walls first.

Be sure to select a filler of good quality and made to use in outdoor situations.

Once you add the filler, let it dry before grinding or sanding it smooth, and then remove any dust.

In addition, adding a waterproofing additive with a wall plaster can be most helpful, if you are considering the wall plaster.

This will help eliminate moisture from penetrating the exterior wall when added to the plaster.

After you are done, let it fully dry before you apply the waterproof coating to the walls.

Step 5 – Apply the Waterproofing Product

You can use a brush or roller to apply the waterproofing agent.

You may need to add a second coat, so be sure to let the first coat dry fully and then add another.

It’s better to be safe than sorry, so adding a second coat is recommended.

Step 6 – Test and Reapply When Needed

If you want to know whether the waterproof coating will actually protect the walls, you will need to conduct a proper test.

Let a few days pass before conducting the test so that you know the coating is fully dry and hardened.

Spray a water hose with the nozzle at a 30-degree angle around the walls of your home.

You’ll want to spray plenty of water, so this may take several minutes up to an hour or longer.

Once completed, use a moisture meter to see if any moisture is present. If not, then the waterproofing worked.

If the meter is detecting moisture, then you will need to address the issue and reapply the waterproofing coat.

Also, after the recommended longevity time has passed, you can add another application over time to maintain the waterproofing qualities of exterior walls.

waterproofing exterior walls products

Problems if You Don’t Waterproof the House from the Outside

From the damage caused by the moisture itself to lichen and algae on the brickwork to mold or mildew forming inside the walls, there are many things that might happen which can cause damage both to the exterior and interior of your home.

If you live in a dry climate, then the waterproofing will be that extra safeguard that will last for a long time.

However, if you live in a moist, humid climate, then you may experience the following issues if you do not waterproof the exterior of your home.


Water that manages to get inside the brick or mortar can freeze and then expand to cause cracks which let additional moisture inside.

Called ‘spalling’, this can also lead to mold and mildew growing inside the cracks which can cause further damage.


Interior walls may become damp from exposure to the excess moisture that has penetrated from the outside.

This means that the material itself can become damaged from the presence of moisture which will need to be addressed.

Plus, the dampness is a magnet for mold and mildew which may consume the organic materials and cause extensive damage.


If you see unexplained white patches on the brick, this is known as efflorescence.

This is a condition caused by damp patches that contain salts. If they seep out to the surface of the brick, they can cause ugly white patches that are difficult to remove.

If they make their way into the plaster, they can damage it from the inside.

Finally, the resale value of your home can be considerably reduced with the presence of mold, mildew, white and damp patches.

They not only make the home look unattractive they are causing damage that must be repaired.

However, the good part is, if you waterproof the exterior of your home, then you can prevent these issues from occurring.

best waterproof paint for exterior walls

How Effective are Hydrophobic Paint Coatings in Waterproofing Exterior Walls?

If you decide to paint the brick or concrete instead of using a sealant, then choosing a hydrophobic paint coating can be of great service.

This type of waterproofing paint for exterior walls actively repels water and comes in a range of qualities that can match your needs.

You can choose a clear coating called masonry crème that lets the original color of the brick still be seen on the outside.

This type of coating will still penetrate the surface and provide ample protection from moisture.

In addition, they can help add to the thermal insulation of the brick and may last as long as two decades before you need to apply additional coats.

A façade coating will cover the brick and add color to the external walls.

This type of paint is breathable which is a good thing as it allows any moisture that penetrates to dry out.

You will need to apply two coats and it will help hide any inconsistencies in the color of the brick itself.

Façade coating will last up to 20 years as well, resisting not only the water but also any dirt or grime that might wind up on the surface.

You can choose from a range of colors that works quite well on brick, stone, and concrete.

Hydrophobic paint can also be used on other materials made from minerals such as roof tiling.

It will provide a waterproof coat that will last for at least a decade. In addition to roof tiles, they can be used on any surface made from minerals.

The Bottom Line

Many problems could occur if you fail to waterproof the exterior of your home.

However, by following the right tips and waterproofing your home exteriors well you can make significant profits, especially if you plan to sell your property in the future.

Hopefully, the above step-by-step guide will prove helpful for making the desired changes.  

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