As the weather cools and humidity rises indoors, bathrooms face a barrage of moisture. One of the most common early warning signs of water ingress is degraded, discolored, or peeling silicone sealant around your bath, shower tray, or basin. Left unaddressed, old sealant allows water to seep directly into surrounding walls and flooring, leading to structural rot and black mold.
Replacing bathroom sealant is one of the most cost-effective DIY home maintenance jobs you can tackle. With the right technique and professional-grade materials from our branches, you can achieve a clean, watertight finish that protects your home all winter long.
Before starting, gather everything required to ensure a smooth workflow:
Completely removing the old bead is vital; new silicone will not adhere properly to old, dirty sealant.
Use your utility knife or a dedicated scraper tool to slice along the top and bottom edges of the old bead.
Pull the strip away carefully in one continuous length where possible.
For stubborn residue left stuck in the joint, apply a silicone dissolver or wipe down with white spirit, then scrape it clean using a plastic scraper to avoid scratching acrylic baths or porcelain basins.
Moisture, soap scum, or grease left behind in the gap will cause your new silicone to fail prematurely.
Scrub the joint thoroughly with a fungicidal cleaner or soapy water to remove any traces of mold or mildew.
Rinse the area completely and wipe it down with a dry cloth.
Crucial Step: Leave the bathroom to dry out completely for several hours (or use a heat gun on a low setting). Applying silicone to a damp joint traps moisture underneath, leading to instant failure.
If you want a factory-standard, razor-sharp finish without smudging silicone onto your tiles or bath rim, use masking tape.
Run a strip of masking tape along the wall, about 3 to 5 millimeters above where the new bead will sit.
Run a parallel strip along the bath or sink edge. This ensures your final bead has neat, uniform boundaries.
Cut the nozzle of your sanitary silicone cartridge at a 45-degree angle. Tip: Start with a smaller cut than you think you need; you can always trim it wider later. The width of the hole should match the width of the gap you are filling.
Load the cartridge into your caulking gun, squeezing the trigger until the sealant reaches the tip.
Hold the caulking gun at a consistent 45-degree angle to the joint.
Squeeze the trigger evenly and pull the gun smoothly along the gap at a steady pace. Avoid stopping mid-run to prevent thick spots or air pockets.
Ensure the silicone makes full contact with both the vertical wall surface and the horizontal fixture edge.
Within 5 minutes of application, wet your silicone smoothing tool (or a gloved finger dipped in mild soapy water) and run it smoothly along the bead in one fluid motion.
This forces the silicone into the joint, removes excess material, and leaves a concave curve that sheds water efficiently.
If you used masking tape, gently peel it away immediately while the silicone is still wet, pulling it away at a 45-degree angle before a skin starts to form.
Keep the bathroom well-ventilated and avoid running the shower or getting the seal wet for at least 24 hours (check your specific silicone tube instructions for exact curing times).
Q: Can I apply new silicone directly over old, moldy silicone? A: Never. New silicone will not bond to old silicone, and sealing over mold simply traps the fungus inside the joint where it will continue to grow and rot the surface underneath. Always strip it back completely.
Q: What is the difference between general-purpose silicone and sanitary silicone? A: Sanitary silicone contains built-in anti-fungicidal agents specifically formulated to resist mold growth in high-humidity environments like bathrooms and kitchens. General-purpose silicone lacks these additives and will turn black with mold much faster.
Q: Why is my new silicone sealant peeling away after a few days? A: Peeling is almost always caused by one of three things: moisture trapped in the joint during application, soap residue or grease left on the surface, or filling a bath with water after sealing (which stretches the bead as the bath dips under weight). Pro tip: Fill your bath with water before applying the sealant and keep it filled while the silicone cures to ensure it doesn't stretch and snap when weight is added later.
