What Are Best Ways to Waterproof Bathrooms

Water damage to homes can be accurately expensive, and it’s not something you could postpone for a later time of the year when you have saved enough cash for the same.

According to HomeAdvisor, water-related repairs at home can cost you an average of $350 to $1200 depending on the material you choose to use when repairing. 

Other costs related to structural damage, mold and mildew handling, and repainting can turn into a costly nightmare if installation specialists do not waterproof the room before and after tiling.

The best way to waterproof your bathroom floor is to use a primer or a sheet membrane, or a combination of both, which acts as bathroom sealing to protect the floor from water penetration. You could use multiple layers of coatings applied in opposite directions for best results, preventing pinhole effect and air entrapments. 

Should bathroom floors be waterproofed?

Bathroom areas are frequently moist. This means that the materials and implements in the bathroom are generally wet for specific times throughout the day.

Consequently, water can seep in or leak into adjacent rooms if not controlled. This will lead to the fast deterioration of your precious interiors. Walls, wood, insulation, and wallpaper close to the bathroom may also become damaged when water causes warping, stains, and bubbling. 

Water is one of the leading causes of structural damage. Continuous seeping of water into your wall reduces wall integrity gradually. It causes buckling of floors. 

Moisture damage on the walls can also cause mold growth, especially in areas not visible. Mold exposure could lead to extensive wall damage and health-related allergies. Mildew, rot, and rust accompany moist environments. Mold, rust, and mildew could also lead to a difficult time handling odor emanating from the same.

Solving issues related to water leakage is also costly. Maintaining walls and interiors damaged by leakages is also an extra expense.

Do you need to waterproof the bathroom floor before tiling?

Tile glue and tile grout on their own cannot naturally protect against water damage to areas beneath them. BS 5385 Part 4 states that the latter component combination alone is insufficient to waterproof wetrooms and bathrooms. They are not a substitute for waterproofing floors before tiling. Water can still leak or seep into adjacent structures and components.

The Tile Council of Northern America has a section on environmental classifications that places the bathroom floor as a heavy moisture exposure area when examined. This categorization helps determine specified installation details and appropriate materials for the installation of tiles.

We can then use an ANSI A118.10 waterproof membrane to keep the area behind tiles dry by categorizing the bathroom floor. It is therefore essential to waterproof the bathroom floor before tiling to avoid facing leakage issues later. It is also easier and saves you a lot of time and money.

How do you waterproof a bathroom floor before tiling?

Waterproofing the bathroom floor involves using a waterproofing system such as a sealer or a membrane on joints and grouts or the floor surface before tiling.

Follow these steps to waterproof the bathroom floor before tiling:

Step 1: Begin by priming the surface and ensuring it is in good condition; it is clean and dry and with less than 5% moisture content. Ensure the surface has little loose material by sweeping and collecting chips and small rock material. Shot blast the surface to increase the grip of the tile. 

STEP 2: You can then seal the floor by first applying a layer of a suitable floor primer. Ensure you cover the whole surface with a layer of primer and that no spots are left. Allow the primer to dry completely. 

STEP 3: If corner pieces and joints exist, apply a silicone bead around the floor waist, around the taps, and the row’s plumbing to allow for movement.

STEP 4: Apply another adhesive layer and place a 200-mm approved membrane on the curves, corners, and even drainage systems. Ensure there are no wrinkles or air bubbles in the membrane. Push the membrane into the corners. 

STEP 5: Apply another second layer of coating to saturate the membrane before the first layer dries completely.  

STEP 6: For the best effect, you can use multiple layers of waterproof sealants applied in different directions to prevent pinholes and air entrapment. Ensure the coating has dried for 30-36 hours before fixing the tile.

How do you waterproof a bathroom floor after tiling?

Waterproofing a bathroom floor before tiling is not sufficient enough to hold backwater. To ensure a foolproof seal, you could also waterproof the floor after tiling. This ensures no water gets underneath the tiles or into the first waterproofing layer. 

Waterproofing after tiling may also be necessary when you realize leakages into the adjacent structures. However, industry professionals do not recognize waterproofing after tiling as a sure method of waterproofing the floor.

Follow these steps to waterproof the bathroom floor after you have fixed your tiles:

Step 1: You could begin by clearing some of the grout joints to prepare for the addition of a sealer. 

STEP 2: Use a ASTM C920 (American Society for Testing and Materials) sealant on the grout joints. Wait for it to dry before continuing with subsequent construction/operation processes.

Can you tile straight onto waterproofing?

Tiling directly onto waterproofing is dependent mainly on the material you use. For example, sheet membranes need an additional layer of primer. Pressure-sensitive and adhesive-dependent membranes usually need a primer on the substrate before tiling. Other waterproof membranes may require cement-based mortar before tiling.

Liquid membranes, however, do not need any primer before tiling. They are just painted, troweled, brushed, or sprayed over the surface. You can now tile directly onto the waterproofing membrane. However, use two layers of coating to ensure a continuous waterproof film. 

There are also emerging technologies such as elastic foam technology, which uses a self-adhesive sealing membrane to adhere directly to walls and floor surfaces without using other sealing material. 

Tile waterproofing sealers

Here are two tile waterproofing sealers recommended for their features.

1. Loctite Polyseamseal White Tub and Tile Sealant

Loctite Polyseamseal White Tub and Tile Sealant, 5.5-Fluid Ounce Squeeze Tube (2241860)
  • Possesses both bonding and sealing capabilities
  • Mold and mildew resistant seal
  • Scrub resistant; Sealant is watertight and paintable
  • Easy to use; Water clean up
  • 5. 5-fluid ounce squeeze tube
  • White  in color
  • Full Cure Time is 24 Hours

2. Seal It Green® Xtreme Impregnating Grout Sealer

Seal It Green® Xtreme Impregnating Grout Sealer-Non-Toxic And Zero VOC's-No More Ugly Black Stains, Food Stains Or Any Stains. Use On Granite, Grout, Tile & Stone. Seals & Protects. Easy To Use Pro Formula. Lasts Yrs.
  • Blocks black spot stains, dirt, and grime
  • Seals and protects grout, granite, tile, marble, and natural stone in showers
  • Non-toxic and zero VOC (no hazardous Fluoropolymer, Silane, or odors)
  • Easy DIY spray

Floor waterproofing membrane

1. Redgard® Waterproofing And Crack Prevention Membrane

Custom Building Products LQWAF1-2 1 Gallon RedGard Waterproofing & Crack Prevention Membrane
  • Ready-to-use elastomeric waterproofing membrane
  • reduces crack transmission in tile and stone floors
  • bonds directly to clean metal drains, PVC, stainless steel, and ABS drain assemblies
  • It can be used under all types of floor coverings.
  • Quick-dry formula
  • Recommended by IAPMO

2. Waterproofing Membrane material

Waterproofing Membrane for bathroom, shower and tile flooring | 3 Ft 3 inch x 33 Ft (1 meter x 10 meter) | 108 square feet | 8 mil thickness | Roll package
  • Enables tile installation directly on top of the membrane
  • Made of soft polyethylene
  • 108 SQ Feet large roll: 3′ 3″ wide x 33′ long (1m x 10m)
  • Crack bridging capabilities

Waterproofing a wooden bathroom floor

Always waterproof wooden bathroom floors after the walls. You could use a urethane waterproof sealer that is water or oil-based. The sealer will protect the floor’s natural shine.

Step 1: Apply the first coat of the sealer using a thick mop made of wool or any other soft natural material. 

STEP 2: Add a waterproof membrane to the floor. Add an extra layer of waterproofing agent so that it acts as an adhesive. This adds integrity to the sealer. Ensure you cover corners and crevices as you proceed. 

STEP 3 Allow the membrane and the first layer of sealer to dry.

STEP 4: Apply another coating layer and let it dry before adding wooden flooring to your bathroom floor. 

Waterproofing subfloor before tiling

Waterproofing methods used before tiling rely on the type of subfloor in the room you are tiling. The subfloor should hold the weight of the tiles and preparation materials required to complete the installation. Follow these steps to waterproof the subfloor before tiling:

Step 1: Fill seams in the subfloor with caulk and tape off any affected vents 

STEP 2: Install cement-based backer board to prevent flexing of the tiles, and you can thus add the tiles.

STEP 3: Add a layer of primer before fixing the tiles. Use a flexible tile adhesive to increase floor substrate flexibility.

Pros and cons of waterproofing a bathroom floor


  • Saves you time
  • Protects your structure from water damages
  • Reduces home renovation intervals
  • It saves you money from repairing water damages
  • It prevents odors and mold, which are health hazards


  • It’s expensive to install waterproofing
  • Some waterproofing materials are not environmentally friendly

Do you need to waterproof a concrete floor?

Yes. Water and moisture can transfer to adjacent floor surfaces since concrete is porous without a sealer. Water can also cause cracks or break off.