How to Waterproof With a Silicone Sealant

Protect surfaces from water damage by applying a silicone sealant.

With many home improvement projects, you're left with a surface that's susceptible to water damage. These surfaces may stain or warp---or the water flowing through can affect something covered by the non-waterproof surface. No matter the reason, it's always less expensive to simply add a waterproof sealant over the susceptible surface rather than pull the surface and replace it with one that offers greater water resistance. Silicone sealant generally serves as a waterproofing agent. A layer of sealant applied to the surface shrugs off the water, protecting the surface and what may lie beneath.

Things You'll Need

• Sponge
• Mild liquid soap
• Rags
• Silicone caulk
• Putty knife
• Liquid silicone sealant
• Hand-pump sprayer
• Squeegee
• Paint roller

Instructions

1. Clean the area you need to seal to remove any dirt or debris that may interfere with sealant adhesion. Wash the area with a mild liquid soap and warm water mixture, then pat the surface dry with a clean cloth.

2. Load the silicone caulk tube into the silicone gun by pressing the release tab on the gun, pulling the pressure tab, then sliding the tube into the gun body. Adjust the gun's trigger to fit the tube size, then squeeze the trigger until the release bar in the gun sits against the tube. Secure the tube in the gun by locking it into place with the locking mechanism on the side of the gun.

3. Cut the tip off the tube at a 45-degree angle, using a utility knife. Twist the tube in place until you can hold it against the surface that you're waterproofing at a 45-degree downward-facing angle, with the tip flat against the surface.

4. Press the tip of the tube against the seam or joint you're filling with the caulk. Press the trigger to release a bead of caulk from the tip of the tube. Move the tube at a steady pace along the joint to fill it with caulk.

5. Wet the tip of a finger and drag it across the caulk to spread it evenly over the joint. Allow it to dry for 48 hours before using the surface.

6. Spray a light layer of liquid silicone sealant over the surface, with a hand pump. Start at the top of the surface and work your way down to the base. Spray the sealant back and forth across the surface as you go, to cover it evenly. Avoid pooling the spray in any one spot.

7. Use a squeegee or low-nap roller to spread the sealant evenly across the surface and seal any pores. Work the sealant in rows, overlapping each row by half the width of the applicator to prevent leaving lines in the surface. Repeat the application a second time to ensure complete coverage of the surface with the silicone sealant. Wait 48 hours for the sealant to dry before using the newly waterproofed surface.

References

• Ask the Builder: Waterproofing Tile Installations
• Online Tips.org: How to Seal Tile Grout
• This Old House: Maintaining Ceramic Tile