How to Waterproof a Bathroom Floor Without Making a Mess

12 September 2016
 Categories: Construction & Contractors, Blog

Any experienced plumber or tiler will tell you that waterproofing a bathroom floor before tiling is essential. Leaving a floor exposed to leaks can cause timber rot and even structural damage. However, bathroom waterproofing can be a messy process! This step-by-step guide will show you how to prepare your bathroom floor for tiling without spending hours cleaning up afterwards.

What You'll Need

Tools and equipment:

  • Safety glasses
  • Indoor broom
  • Spirit level
  • Utility knife
  • Paint roller, brush, stirrer and scraper


  • Painters' tape
  • Reinforcing fabric
  • Primer and additive
  • Silicone sealant
  • Waterproofing agent
  • Under-tile waterproofing membrane

Step 1: Clean up!

Before getting started, make sure the bathroom floor is clean. Getting dirt or dust into your waterproofing membrane can interfere with the bonding process and prevent it from sticking.

Step 2: Apply the primer

Next, pour the primer into the roller tray that came with your paint roller. Use your paint roller or brush to apply the primer to the walls surrounding the area you wish to waterproof, up to a height of about one foot, then apply the primer to the bathroom floor. Some tilers skip this step, as the primer can take several hours to dry, but priming helps strengthen the membrane bond and is recommended by the Australian Institute of Waterproofing.

Step 3: Apply the silicone, then wait...

Wait until the primer has dried, and then apply the silicone around the edges of the floor, to seal the gap between the floor and the wall. If there are any gaps on the floor, seal those as well. It is a good idea to scrape off any excess silicone using your paint scraper. Do this before allowing the silicone to dry - this is because silicone can be messy to remove once cured, and attempting to do so can cause damage to your bathroom.

Then, allow 24 hours for the silicone to dry. In drier climates, such as regional Western Australia, the silicone may take longer to cure, so allow up to 48 hours to be sure. While you are waiting, you can affix painters' tape to the wall at the level up to where you applied the primer.

Step 4: Apply the waterproofing agent and membrane

Next, use your paint roller to 'paint' the waterproofing agent onto the wall, from the floor to the masking tape. Then, apply the agent to the floor where it meets the wall.

Now, cut the membrane cloth into four portions, each one the length of one side of the bathroom wall. Lay the membrane in the corner where the floor meets the wall, such that half of the membrane is on the floor and the other half on the wall, and the silicone is covered. Paint over the membrane with the waterproofing agent, and repeat for each wall of the bathroom. Then, paint the rest of the floor with one coat of waterproofing agent, and leave to dry for 24 hours.

Step 5: One more coat

Lastly, apply a final coat of waterproofing agent to the floor and the part of the wall under the painters' tape. Once this second coat has dried, the waterproofing is complete, and you are ready to start tiling! For more information, contact companies like Westside Sealants Pty Ltd.