- Difficulty
- Easy
- Time
- 2 hours, plus 24 hours curing
- Parts
- $15 – $30
- To hire out
- $200 – $400
The seal where a bath or shower meets the wall is the only thing stopping water getting behind the tiles. When it splits, blackens or peels, water goes into the wall cavity, and the damage is invisible until it is expensive.
Re-caulking is cheap and quick. Almost every failed job fails for the same reason: the old caulk was not fully removed, or the new bead was laid into a damp joint.
How to tell this is your problem
- Black mould spots along the caulk line that keep returning after cleaning
- The bead has lifted, split or pulled away from the wall or tub
- Water pools behind the seal, or the wall below feels soft
- The caulk has gone hard and brittle rather than staying flexible
Should you do this yourself?
Yes, easily. The whole job is removal, cleaning and one careful bead. The main discipline is drying time: caulk needs a genuinely dry joint and 24 hours before the shower is used again, and rushing either is why beads fail.
Stop and call someone if
- The wall behind the tiles feels soft or spongy. Water is already in there and caulk will seal the damage in rather than fix it.
- Tiles are loose or grout is missing over a wide area. Caulk is not a substitute for either.
- The tub or base itself moves when you step in. That flexing will split any new bead within weeks.
What you need
Tools
- Caulk removal tool or sharp scraper
A plastic one will not scratch an acrylic tub the way a blade will.
- Caulk gun
A dripless one with a smooth trigger gives far better control than the cheapest ratchet type.
- Utility knife
For cutting the nozzle. Cut small - you can always enlarge the hole, but not shrink it.
- Masking tape
Two lines either side of the joint gives a crisp bead with no skill required. Pull it while the caulk is wet.
Materials
- 100% silicone caulk, kitchen and bath grade
Silicone, not acrylic latex. Latex is easier to tool and paint but will not survive constant wetting.
- Rubbing alcohol
A final wipe after cleaning. It removes soap residue and flashes off, leaving a genuinely dry surface.
Step by step
- 1
Remove every trace of the old bead
Cut along both edges and pull the bead away, then scrape until no residue remains. New silicone will not bond to old silicone, so anything left behind becomes a channel for water. This is the step people rush and the reason most re-caulk jobs fail.
- 2
Kill the mould and clean the joint
Scrub with a bleach solution or a proprietary mould remover and let it work. Mould left in the joint grows back through the new bead within months.
- 3
Dry it thoroughly
Wipe with rubbing alcohol and leave the room to dry for several hours - overnight if the bathroom has no window. Silicone applied to a damp joint will not adhere, and this is the second most common cause of failure.
- 4
Fill the tub before you caulk
Counterintuitive, but a bath full of water sits lower than an empty one. Caulking under load means the bead is not stretched every time the tub is used, and it lasts years longer.
- 5
Tape and lay the bead
Run masking tape a few millimetres either side of the joint. Cut the nozzle small at 45 degrees. Draw the gun steadily along the joint, pushing rather than pulling, keeping constant pressure.
- 6
Tool it, pull the tape, then wait
Smooth the bead with a wet finger in one continuous pass. Remove the tape immediately while the caulk is wet. Then leave it 24 hours before the shower is used - silicone that gets wet mid-cure never reaches full adhesion.
Mistakes that cost money
- Caulking over the old bead. It looks quicker and fails within a season.
- Applying to a damp joint. Silicone needs a dry surface, and bathrooms rarely dry as fast as people assume.
- Using acrylic latex because it tools more easily. It cannot cope with constant wetting.
- Caulking an empty tub, so the bead is stretched every time someone gets in.
- Using the shower the same evening, which ruins an otherwise good job.
When to call a professional
Call a renovation contractor if the wall behind the tiles is soft, if tiles are loose or grout is missing over a wide area, or if the tub flexes underfoot. All three mean water has already got in, and sealing the surface traps the problem rather than solving it.
Hiring a renovation contractor
What Ontario requires, how to verify it, and what the work should cost.