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Can You Waterproof a Wall From The Inside? 9 Effective Ways

When it comes to building your dream home, waterproofing isn’t among the most exciting parts, but it’s certainly vital to a safe and comfortable result. When you expose exterior walls to rainwater or high humidity, the moisture can travel through the masonry and affect your internal walls.

Walls that stay damp for an extended period before drying may lead to mold growth and irreparable damage. But, can you waterproof a wall from the inside?

It is possible to waterproof a wall from the inside. You can prevent issues with water ingress & penetrating damp by waterproofing your inside walls with internal waterproofing products. Thankfully, there are several tricks for waterproofing your interior walls.

To make sure you’re choosing the correct waterproofing method, you need to figure out if the moisture is coming from the outside or if it’s high humidity that’s condensing on your walls.

What Causes Wet Walls Inside Your House?

Wet walls happen when there’s excess moisture coming in, and it can’t get out of your house. You can blame the massive temperature difference between the outside air and the air inside. It stimulates condensation and moisture in walls.

The other causes of wet walls are:

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  • floods
  • pipe or roof leaks
  • improper insulation, etc.

These can all create a ton of water buildup inside your walls – encouraging mold growth and drywall stain, which can cause a bunch of problems down the line. Here are just a few of them…

Quick Tip: If you’re wondering what kind of drywall to use in your basement, check out my article here. Or if you want to use drywall in your bathroom, read my article here before making a start on the project.

The Damaging Effects of Moisture Penetration

  • Health and Hygiene – When mildew, fungus, and mold form, they introduce harmful spores in the air.
  • Room Climate -The uncomfortable chill and dampness causes reduction of heat insulation which increases heating costs. 
  • Costly Repairs – Damaged wall surfaces and ceilings can cost a lot of money to repair or replace. 
  • Insect Infestation – mold attracts bugs. If they live long enough in your walls, they will damage the whole house structure from inside out! It’s an expensive fix that requires demolition & rebuilding.
  • Structural Effects – Moisture damages timber elements, interior plasterwork, and finishes.
  • Weaken Structural Integrity – The moisture can cause the wall to move, buckle, or bend, leading to cracks in your foundation. It may lead to an expensive repair.
  • Stain Marks will remain on the wall forever.

As you can see, it is definitely worth making sure you prevent these things happening in the first place, and one of those ways, is to waterproof internally…

9 Types of Interior Waterproofing

You can waterproof your interior walls, which may solve the problem. But ensure you choose the right products. Here are 9 legitimate and effective products that you can consider to waterproof your interior walls…

#1: Cementitious Tanking System

This is the most common and cost-effective method of waterproofing. It’s a simple process that involves applying two coats of cementitious products onto your interior wall to make it completely water-tight.

HOW IT WORKS: The first layer allows the pores in the brick or stone veneer to remain open, whereas the second layer seals them shut & stops dampness from seeping. 

Most products contain an acrylic polymer that imparts improved strength, bonding, and abrasion resistance. After hardening, the cementitious product becomes a vapor-permeable and water-tight coating capable of withstanding water pressure. The cementitious tanking system helps create warm, waterproof, and habitable spaces.

#2: Grouting

Grouting is another interior waterproofing technique that stops water from passing through cracks and pores in your wall. It involves injecting a unique adhesive into the walls, which dries up to form a tremendous waterproof sealant. 

Since grout contains small amounts of sand, it needs protection from a sealant to last. Sand is porous, having small holes where dirt and bacteria can remain. The best sealers block these holes as much as possible. 

Sealing the grout helps extend the look, texture, and consistency of your grout. It also prevents mildew and mold. You don’t need to hire professionals for this process because you can typically accomplish the job in just a few hours when you use the right products.

Be sure to use a professional grouting kit like this one on Amazon to help get a nice neat finish.

Grouting effectively waterproofs interior wall

#3: Plastic Sheets and Panels

It is a less common waterproofing technique that involves sealing the walls from any water penetration. It’s also called weatherproofing and requires an excellent working knowledge of materials, tools & equipment. They don’t stop water from getting through the wall, but they do stop it from ruining things in your house.

Water that gets through walls runs down the back of the plastic into a drainage system. The process may sound easy, but it can be very tedious as well as time-consuming because you have to cover every nook and cranny with plastic sheets

#4: Silicate-Based Concrete Sealers

The process of applying this method involves spraying a layer of silicate-based sealer on your walls. It is suitable for unpainted walls. The sealers soak in and chemically react with ingredients in the concrete or brick, forming a rugged, waterproof surface. Because these are penetrating sealers, they can’t flake off or peel, and you can paint over them. 

Applying a silicate-based sealer with a brush, roller, or sprayer is easy enough for a DIY project. It creates a robust and waterproof barrier that blocks moisture from the inside brick or stone veneers. This one available at Amazon is very effective.

#5: Concrete Waterproofing Coatings

These are a modern waterproofing option that creates rigid surfaces on your exterior walls. It involves applying a special liquid onto the concrete, which then dries to form an even coating over it for protection against water damage. 

Since these coatings seal and protect exterior masonry from moisture & provide better adhesion of paint or other finishes, they also act as a protective coating from mold, mildew, and damage. It’s an easy job- apply the layer with a heavy brush made of Tampico bristles – a natural fiber that’s stiff enough to get the job done.

#6: PVC Panels

The membranes of PVC-P (polyvinyl chloride) flexible used in waterproofing of walls come with sophisticated technology and high security. They protect the building from the destructive influences of the water.

Depending on the aspect of water (moisture, time pressures, or permanent pressure), the sealing system must adapt to them. Experts express it in the thickness of the membrane, a control system, and compensation.

When it comes to the potential influence of permanent water pressure, You must provide at least a 2 mm thick membrane. It’s durable & offers excellent insulation against heat or cold, especially when combined with high-quality wallpapers on top of them.

#7: Waterproof Paint

Waterproof paint helps to prevent water from penetrating your walls & ceilings, but it’s only a temporary fix and needs retouching every couple of years. Waterproofing paint coats walls to stop water damage.

It’s available in an easy-to-apply paint form that dries into a waterproof barrier on the surface of your wall or ceiling. Waterproof paints are usually latex, acrylic, or oil-based. They can be used inside & outside for protection against moisture, although some require two layers with adequate drying time between them.

#8: Drywall Joint Treatment

You can spray or brush this solution (Amazon link) onto your drywall joints before taping them with mesh tape for protection against water damage. It’s a moisture-resistant formula that helps seal cracks and crevices around the drywall seams, corners, and joints for good waterproofing protection from inside your home.

#9: Breathable Paint

The paint effectively protects against penetrating damp in bathrooms or kitchens where humidity & condensation are significant problems. It’s a water-based, breathable paint that allows moisture vapor to pass through it while stopping liquid water from penetrating the surface of the wall or ceiling.

In most cases, these paints are latex-based, but an oil-based option is also available for high humidity environments with lots of condensation.

10 Simple Wall-Waterproofing Steps

  • Step 1 – Clean the area with a damp cloth to remove any dust or dirt. If your walls are filthy, then you may need to use a degreasing solution or mild detergent for this stage. Let the walls dry before you proceed to ensure good adhesion between the waterproofer and the substrate.
  • Step 2 – Protect your floor from drips and spills by putting down old sheets of cardboard around the room. 
  • Step 3 – Put on safety gloves, eye protection, and a dust mask before filling the syringe or brush with a waterproofing solution.
  • Step 4 – Select the suitable waterproof and mix the sealant using a drill and paddle mixer attachment.
  • Step 5 – Apply the waterproof with a paintbrush or a roller, covering all of your walls and window frames or trim evenly in small sections at a time. Allow it to dry for around 30 minutes before you apply the second coat.
  • Step 6 – When the wall is arid, use a damp sponge to remove any excess waterproof that may have seeped through tiny cracks or gaps.
  • Step 7 – The next step involves adding an extra layer of protection by putting down tape on top of the newly applied waterproofing product before applying paint over it with your roller brush for full coverage.
When it comes to damp and mold in your home, prevention is always the easier and less expensive option
  • Step 8 – Use a roller or paintbrush to apply your chosen paint color over the tape. Let it dry for around half an hour before removing the tape and adding any final touches with a fine detail brush for touch-ups.
  • Step 9 – Use sandpaper to smooth down any bumps, lumps, or sharp edges from your painted surface at this stage.
  • Step 10 – The last step is to cut in around window frames & other areas that require a more refined finish with your brush or roller before cleaning up any drips or spills, taking off the sheets of cardboard, and calling it done!

The final step is drying out your work area by opening any windows and turning on fans or heaters for at least 48 hours while avoiding touching or wiping away any paint before it’s wholly dried.

NOTE: Conducting a water-tightness test is critical to evaluate the products’ effectiveness for waterproofing interior walls. For this test, water should be sprayed on the wall surface for a couple of hours, keeping the nozzle at a 30-degree angle. Your walls pass the test if the damp meter shows there is no moisture penetration.

8 Ways to Prevent Moisture in Walls

Damp walls can cause a whole host of problems in your house equally caused by different things, from penetrating or rising dampness in your walls to cavity wall’s structure and a possible leak somewhere in your home.

To avoid damaged walls and expensive repairs, here are 8 ways you can prevent moisture in your wall…

#1: Proper Ventilation

Without adequate ventilation, interior moisture in walls can cause mold and mildew to grow. Therefore, you should keep windows open as much as possible, especially during humid seasons such as summer when the humidity levels are high.

You can also use vents to enhance the ventilation in your house. It’s essential to ensure that your apertures go directly outside and not to your attic, where the moisture will cause more significant problems.

Various vents are available in the market, some even with timers or moisture sensors to run long enough to remove the excess moisture from the room.

#2: Use Vapor Retarders

Another way to deal with the moisture issue is by using a vapor retarder, which prevents water from passing through your walls. You can install it behind drywall or plaster as well as over concrete block and brick veneers.

Different materials are available for wall cavities, such as polyethylene sheeting, metal lath, and fiberglass sheeting. Ensure that you use a vapor retarder with suitable permeability properties to prevent moisture in walls. Here’s a great example of a good one on Amazon that is durable and strong.

#3: Get a Dehumidifier

Secure your house with a dehumidifier to dry out the excess moisture. A dehumidifier sucks in excess vapor in a room and prevents dampness and mold growth. They are available in different sizes and shapes, so you can choose one that fits your needs perfectly.

Some dehumidifiers are portable (means you can move them around the house), like this one available at Amazon. While others are large enough to be placed in a room, like this one (Amazon link).

#4: Improve Your Insulation

A water-tight building requires proper insulation to prevent moisture from rising into the cavity and affecting your internal walls.

Cavity wall insulation prevents dampness in your interiors. It ensures you save on energy bills by keeping heat loss at a minimum, thus improving thermal comfort for house occupants and preventing mold growth and deterioration of internal walls.

#5: Repair Any Leaks

If you find any leaks in your home, then do not neglect them. Fixing the roof will prevent water from seeping into your cavity walls and causing moisture. You can also get a plumber to check for other minor or major leaks around the house that may be affecting its structure.

#6: Invest in Quality Construction Materials

When building your dream home, it’s crucial to invest in quality construction materials. If you choose the right waterproofing products for exterior walls and take care of your house correctly, then you will prevent moisture in walls that may lead to mold growth or, worse still, rot damage.

Different materials hold and pass water differently, so ensure you choose suitable construction materials for your home.

#7: Prevent Moist Foundation

Foundation is another vital part of your house that needs proper care and maintenance. If it becomes weak, then there may be a possibility that the walls above could collapse and cause irreparable damage to internal walls.

You can prevent this by having regular inspections on your foundation at least once every year or after heavy rainfall when moisture levels are high.

Check out my article, “How Do I Stop Water Coming Through my Floor?” for extra information.

#8: Use Good Quality Paint

Another way to protect the walls from moisture is by coating them with a good quality paint. The varnish will prevent water absorption and provide another layer of protection that prevents molds growth.

However, ensure you choose the right type of paints for your house as different paints are made specifically for homes in other regions due to climate conditions


Do not wait for the arrival of the monsoon season; prepare and protect your home from moisture and water leakages. You can waterproof your wall from the inside with genuine waterproofing products and enjoy the beauty of rainfall.

With proper maintenance and care of your house,  you can prevent moisture in walls and keep your home safe, comfortable, and damage-free.

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