Do I Need to Waterproof My Whole Bathroom? (Paint, etc.)

Waterproofing your bathroom protects you from water damage and mold. There are several options for waterproofing your bathroom floor, ceiling, walls, and fixtures including paint, tile, and waterproof membranes.

You should waterproof your ENTIRE bathroom. Bathrooms are highly susceptible to mold and mildew growth that can be hazardous to your family. Water leaks are expensive to repair and can lead to long-term structural damage in your home. Waterproofing your entire bathroom is a safe and smart choice for your home.

Each area of your bathroom requires specific materials to make it waterproof. Are you ready to learn about the best supplies and applications to waterproof your bathroom walls, ceiling, and floor? 

What Areas of My Bathroom Should I Waterproof?

If you do not want to waterproof the entire bathroom, the top places to waterproof are the bathroom floor, shower walls, shower step-down, and bathroom ceiling. These areas are most susceptible to water damage that can result in structural damage and mold.

Shower and Bathroom Floor

You will need the following materials to properly waterproof your bathroom floor:

  • Rolling brush and paint trays
  • Waterproof primer
  • Bonding agent
  • Waterproof sheet membrane
  • Silicone caulk
  • Personal protective equipment
  • Painter’s tape

Before you begin, put on gloves, safety goggles, and a face mask. You will be applying a bonding agent and membrane 4-5 inches up the wall. Tape off this height on all the walls in the room. Make sure the cement or the subfloor is clean and free from dirt or dust. 

Begin by rolling on a thin layer of waterproof primer all over the floors and 4 inches up the wall. Allow the primer to dry and then fill in all cracks and seams with silicone caulk. The primer and caulk must be fully dry before moving on to the next step. This usually takes 24 hours. 

Next, you apply the bonding agent or adhesive. Begin by working from the back of the room forwards. As you roll on the adhesive, cover it with the sheet membrane. Apply another coat of adhesive to the top of the membrane. Allow this to dry for 24 hours. Follow up with a second coat. Wait another 24 hours for that to dry. Your bathroom floor will be waterproof and ready for flooring.

Shower Walls

Ready to waterproof your shower walls? Here is a list of materials you will need:

  • Rolling brush and paint trays
  • Liquid membrane
  • Silicone caulk
  • Personal protective equipment

Put on your protective gear and double-check your shower wall backing. Make sure that all holes and cracks have been patched and that the surface is clean and smooth. Stir the liquid membrane well. Water tends to settle at the top of the container. Mix that into the agent carefully.

Begin by rolling on the waterproof liquid membrane. Take care to get in the corners and cover every spot of the shower wall backing. Allow this to dry for 24 hours. Repeat with a second coat. 

Any cracks should be sealed with silicone caulk. This includes where the tile or acrylic shower covering will meet the wall at the top. It also includes where the tile will meet the bathtub or floor. 

Step Down

If you have a step-down or shower pan, you have to waterproof it. Otherwise, you are at risk for serious water leaks. This job is messy! Wear clothes you don’t mind getting dirty in. 

You will need the following supplies to waterproof the step down in your shower:

  • Deck mud
  • Trowel
  • Pan liner
  • Staple gun
  • Silicone caulk
  • Razorblade

Start by pre-sloping the floor. You want the water to run towards the drain. Do this by placing your level at the slope you want the floor to be on. Use the deck mud to create the slope. Make sure the deck mud is smooth. Allow this to dry.

Next, cover the deck mud with a pan liner. You will want the liner to go up the wall 6-7 inches and cover over the step down. Make sure you have identified where the drain is and pre-drill the holes for the screws. Do not cut the pan liner around the drain hole until you are finished. This will prevent any debris from going down it.

Once the pan liner is in place, use a staple gun to secure it to the walls and floor lip. You want to staple 2 inches up the wall so that it is attached above the waterline. Fold in the corners as you go. Do not cut the pan liner. This leaves a chance for holes or missed coverage. 

Remove excess with a razor blade. After your pan liner is secured, the step-down is ready for the shower pan or tile. 

Bathroom Ceiling

Your bathroom ceiling is vulnerable to mold and mildew if it is not waterproof properly. There are several options for waterproofing your ceiling, however, the fastest and easiest is to use liquid membrane and waterproof paint. You will need these supplies:

  • Rolling brush and paint tray
  • Waterproof liquid membrane
  • Waterproof primer
  • Waterproof paint

Clean the ceiling with a damp sponge. Do not over-saturate it with water, but make sure it is clear of dirt and dust. Begin by rolling on a layer of waterproof liquid membrane. Make sure to cover the entire ceiling area. Allow the first coat to dry for 24 hours. Then apply a second coat. Wait another 24 hours so it can dry completely.

Next, paint over the liquid membrane with a waterproof primer. The liquid membrane is usually pink or red. In addition to the extra waterproofing protection, the primer will make it easier to apply your ceiling paint color without worrying about stains and bleeds.

Once your primer is dry, apply a coat of waterproof paint. Depending on the brand and formula you choose, you may need to apply two coats. Allow the paint to dry in between. 

These steps are secondary to having a bathroom fan. Bathroom exhausts are crucial to removing moisture from the bathroom. Steam is sucked out of the exhaust and prevents moisture from settling in your bathroom walls, ceilings, and fixtures.

Why Should I Waterproof My Entire Bathroom?

Waterproofing your entire bathroom protects your home from water leaks that can lead to serious (and expensive!) structural damage. It also eliminates the risk of mold and mildew. Bathrooms have an extremely high level of moisture.

Aside from the obvious running water in the sink, bath, and shower, steam is an even bigger danger. Small water droplets move through the air and settle in your ceiling, walls, and floor. Waterproofing your bathroom will prevent costly repairs and serious health risks in the future.

Protects Bathroom Tiles, Grout, and Fittings

Tiles are waterproof. However, the grout between the tiles is not. By waterproofing before laying down tile and grout, you prevent water from seeping under the tiles. This prevents mold from growing. It also protects your tiles from lifting or cracking.

Bathroom fittings can also be a source of water damage if not installed correctly. All fittings should be sealed with silicone caulk. This prevents water from getting between the fitting and tile in your shower and bathtub. It will protect your tile from damage and prevent mold from growing on the walls or floor.

Prevents Mold Growth

Mold spores love humidity. The combination of moisture and heat in your bathroom creates a breeding ground for mold. Waterproofing your bathroom will prevent mold from growing. It blocks water from getting under tiles and ground and from growing in the walls or ceiling.

Regular sheetrock does not safeguard against mold. Waterproofing your bathroom walls and ceiling protects you and your family from hazardous spores that cause severe health problems including chronic coughing, trouble breathing, and persistent headaches.

Stops Leaks

Water leaks can cause serious structural damage to your home. These repairs are costly and disruptive to you and your family. Undiscovered water leaks will lead to rot. If the damage is really bad, you will need to replace the entire subfloor and sheetrock of your bathroom. This will be an entire floor-to-ceiling gut renovation. Waterproofing your bathroom will stop water leaks and save you money by avoiding costly repairs.

What Can I Use To Waterproof My Bathroom?

Before you begin a bathroom renovation, consider using waterproof materials. There are waterproof options for flooring, paint, and bathroom walls that will protect your bathroom from water damage and mold.

Waterproof Paint for the Shower and Walls

There are several options on the market for water-resistant paint and primers that can be applied to drywall. Here are some of the best choices based on customer reviews.

PaintSizeTypeMildew ResistantWaterproofWater-ResistantPrice
Zinsser Perma-White1-GallonWater-BasedYesNoYes$43.00
Benjamin Moore Bath & Spa Pait1-GallonAcrylicYesNoYes$44.00
PrimerSizeTypeMildew ResistantWaterproofWater-ResistantPrice
KILZ Mold & Mildew1-GallonWater-BasedYesNoYes$38.00
Rust-OLeum Mold Killing Primer1-GallonWater-BasedYesNoYes$49.00

There are also waterproof paints that can be applied over tiles and acrylic shower walls. The top brands are listed below. 

PaintSizeTypeMildew ResistantWaterproofPrice
Rust-OleumTub & TileAerosol6 Spray CansEpoxy AcrylicYesYes153.00

Water-Resistant Flooring

The top choices for water-resistant flooring are ceramic, porcelain, stone, luxury vinyl, and engineered hardwood. The most common bathroom flooring is ceramic. That is because it is water-resistant, affordable, and available in a wide range of colors and styles. Stone is the most expensive choice for water-resistant flooring and also requires the most maintenance. This chart outlines the average starting cost per square foot of each type of water-resistant flooring. 

CeramicPorcelainStoneLuxury VinylEngineeredHardwood

Silicone Caulking

Silicone caulking is an expensive and effective solution to waterproof cracks, seams, and fittings in your bathroom. Run a bead of silicone caulk along every seam where the tile meets the wall or the floor. Take care to caulk around each fitting including faucets and drains. This will prevent water from getting behind tile, acrylic shower walls, and under shower pans. Silicone caulk will wear down with time. Reapply silicone caulk whenever you see it crack or lift.

Exhaust Fan

Every bathroom that has a shower or bathtub needs an exhaust fan. Exhaust fans provide necessary ventilation to prevent excess moisture from causing damage to your bathroom. They expel humid air through a vent in the ceiling.

This prevents mold and mildew growth. You should turn the exhaust fan any time there is steam in the air. It should run while you are in the shower or bath. Some models even come with a humidity sensor that automatically turns the fan on when the humidity level gets too high in the room. Installing an exhaust fan is an essential step in waterproofing your bathroom.

Tile Walls

Tiles are water-resistant. They repel any water or steam that hits them. This helps in preventing mold and mildew. Water will just slide down tiled walls. In comparison, water, especially steam, sticks to drywall. This creates a breeding ground for mold. 

Tiled walls are also much easier to clean and wipe down. Ceramics and porcelain are very durable. You can use powerful cleaners and disinfectants without worrying about eroding the tiles.

While tiles are water-resistant, grout is not. It is important to follow the steps to waterproof your walls before applying tile. This will prevent water that could seep through grout from causing any damage. There are also waterproof tile sealants that can be applied over tile and grout for extra protection. 

Waterproof Systems for a Bathroom

Several waterproofing systems are readily available for purchase at your local hardware store. The primary difference between them is the application process. 

Sheet Membranes

Waterproof sheet membranes are thin material that repels water. Sheet membranes can be applied to bathroom ceilings, walls, and floors. If installed correctly, waterproof sheet membranes are virtually waterproof. They are the preferred method for waterproofing floors in bathrooms. 

You will need to use a bonding agent to attach the sheet membrane to the concrete or subfloor in your bathroom. While this is an extra step in the installation process, the results are extremely effective. Sheet membranes guarantee an even application of waterproofing material with no bumps or ripples.

Fluid Membrane

A waterproof liquid membrane is a liquid rubber that solidifies to a flat surface once dry. It works much the same as sheet membranes. However, fluid membranes are easier to apply and are just painted onto your bathroom walls, ceiling, and floor. 

You must apply fluid membranes in even layers. It also needs to be stirred well to avoid bubbles. The waterproof liquid membrane takes at least 24 hours to dry. You should apply two coats to your bathroom to ensure you didn’t miss a spot. 

Pre-Sloped Shower Pan

If you have a step down in your shower, you want to make sure that the water flows towards the drain. This reduces the height of the water line along your shower walls. It also prevents overflowing and water splashes from settling on your bathroom floor. You can manually slope your shower floor by using deck mud and a level. 

An easier way is to purchase a pre-sloped shower pan. Once installed, this will help the water run directly toward the drain of your shower floor. 

Do I Need To Waterproof My Entire Bathroom?

Your bathroom is highly susceptible to water damage, mold, and mildew. Waterproofing your entire bathroom saves you money on costly repairs and protects your family from the health hazards of mold. 

It is expensive to waterproof your bathroom, but worth it in the long run. Here is a price breakdown of waterproofing materials and the total cost for a 40 sqft bathroom with a standing shower.

MaterialPrice to Cover 40 Sqft Bathroom
Bonding Agent for Sheet Membrane$23.31 (1 gallon)
Waterproof Sheet Membrane$14.69 (1 roll, 33.5’ long)
Liquid Membrane$318.99 (5-gallon)
Silicone Caulk$3.58
Ceramic Tile$365.00 (floors & ¾ up walls)
Exhaust Fan$65.00
Waterproof Primer$37.98 (1-gallon Kilz Mold & Mildew)
Waterproof Paint$43.00 (1-gallon Zinsser Perma-White) X2 = $86.00
Pan Liner$24.00
Pre-Sloped Shower Pan$541.00
Total Materials Needed$1,542.09

Waterproofing your entire bathroom will protect your home from water damage, mold, and mildew. While materials can be costly, you will save money by preventing any future repairs that may have been caused by water damage. Once you have waterproofed your bathroom, there is little maintenance required outside of your regular cleaning routine. 

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