How to Waterproof Interior Walls (from the Inside)

Author: Pat Freling | Updated: | Affiliate links may be present.

Consistent moisture or interior pipe leaks can quickly degrade the integrity of a wall. Without taking proper precautions, you run the risk of mold, mildew, peeling paint, and whole wall repair.

Waterproofing your interior walls can be done for a variety of reasons such as: living in a particularly humid climate, seeing consistent water damage in a bathroom or kitchen, or exterior masonry cracks that allow moisture to seep in slowly to the inside.

Walls that face the exterior of your house should already be waterproofed by the builder, but if you find a flaw in that design or you need to waterproof an interior wall, you can repair and prevent water damage on your own without hiring a contractor.

Waterproofing Steps

You need to work from the inside out to achieve a thoroughly water-resistant interior wall. Don’t just start applying products without the proper preparation.

Find the Source of the Moisture

Before you apply or install any sort of waterproofing product, you have to find the root cause of the issue. This is fairly easy for certain areas like a bathroom or kitchen because those walls are expected to be exposed to water.

But it can be a bit trickier when you are dealing with some sort of plumbing leak or a crack in your exterior masonry. You need to repair these areas to prevent future problems. Simply waterproofing your walls won’t eliminate the risk of mold and structural damage behind the drywall.

Basements are notoriously moist (I know, I hate that word too) so upon moving in you should definitely make a plan to seal the concrete on the inside.

Be sure to check thoroughly around window sills and door jams as well and repair any cracks you see. Don’t forget your gutters and drainage systems as well.

Invest in Drainage Systems

If water in your basement is the main concern, consider investing in a sump pump. Sump pumps are simple, below-ground pumps that will pull water away from your basement walls and pump them out away from your foundation.

If you don’t have a basement, exterior gutters are a worthy investment as well. Foundational decay from excessive water isn’t the only issue homeowners run into. Consistent draining over doors and windows can cause problems on interior walls as well.

Fix All Cracks

Cracks in your drywall can be easily repaired with either joint tape or drywall putty. Find the crack or seal and apply the product as directed.

Once everything is dry, you can sand it as you would for normal drywall repair and seal it with a good drywall sealer or go straight to your waterproof primer.

For cracks in your basement walls, you should apply a concrete sealer or liquid rubber to prevent any further seepage.

Replace Materials If Possible

Instead of sealing and applying waterproof paint to your bathroom or kitchen backsplash, you could consider replacing the materials on the walls altogether. There are many types of waterproof tile you can choose from for this project.

This is a good idea if you are being proactive about your waterproofing needs. Just be sure to repair any existing damage first.

Opt for Water Resistant Drywall

Drywall is made in such a way that it won’t ever be completely waterproof. But there are different types of drywall that are more suited for damp environments that would be a great option for areas in your home that have consistently shown signs of water damage.

Traditional home drywall is white. But there are also blue, green, and purple varieties. Blue drywall is commonly used in bathrooms. Purple drywall will give you the highest level of moisture resistance as well as combat mold and mildew growth.

Seal Your Walls

If your walls are already painted, you will want to remove the paint before applying any kind of sealant. A good sealant will form a protective barrier over the drywall and will give you a great base to paint on.

You can use this on its own or underneath a backsplash.

If you are working in a basement, make sure you are working with bare concrete. Grab yourself a deep penetrating concrete sealer and apply it with either a roller or by spraying it on. Concrete is known to be porous, and these sealers help to fill in all the microscopic pores that are the source of attracting moisture.

Explore Your Paint Options

Once you’ve done the work to locate the source of the moisture and repair all entry points of water, you can finish out the project with a solid waterproof primer and paint.

Your local hardware store will have a wide variety of options for waterproof primers to apply under your paint. This will significantly increase the waterproofing quality when used in combination with a drywall sealer.

Some paints are marketed as being specifically formulated to be waterproof, like most products from the Watertite brand. While these are great products, you are limited in color options which could be a problem when you are attempting to do a full remodel.

Emulsion paints are a popular choice for moisture-prone areas. These are water-based paints with color pigments suspended in them. Once applied the pigmented particles group together to form a solid, even finish. You will find more color options with this type of paint as well.

Things to Consider

As mentioned earlier, most waterproofing of walls should be done during the construction process of your home. If you are planning to waterproof your interior walls after a remodel or a repair from previous water damage, make sure you only waterproof what you need to. Otherwise, it is a waste of time and effort.

Be sure you understand the difference between waterproof and water resistant. Both are beneficial in stopping damage from moisture, but water-resistant products can still show signs of damage if not applied correctly.

If you aren’t using a drywall sealer, you should use a waterproof primer. They work best in unison, but to achieve water resistance, you need to pick at least one of these products.

Truly waterproofing products will be limited to masonry sealers, as they come in specialty materials such as resins or liquid rubber.

Avatar photo

About Pat Freling

Pat has been into DIY painting since he was 14 years old. He's painted interior walls, decks, patio, and even the first car that he'd purchased at 18.

Leave a Comment