How to Re-Caulk a Bathtub or Shower So It Stays Sealed

The caulk line where your tub or shower pan meets the tile does more work than it gets credit for. It keeps shower water out of the wall cavity, the subfloor and the ceiling below. Once it cracks, peels or turns black with mildew, water starts sneaking behind the tile every time someone showers. Re-caulking is one of the cheapest, highest-value jobs a homeowner can do, and with a little patience the result can look as clean as a professional bead.

Difficulty: Beginner · Time: 2–3 hours of work, plus 24 hours of cure time

Tools and materials

100% silicone kitchen-and-bath caulk with mildewcide (white, almond or clear to match)
Caulk gun with a smooth, dripless trigger
Plastic caulk removal tool or a plastic putty knife
Utility knife or a razor scraper with fresh blades (use carefully on acrylic and fiberglass tubs)
Silicone caulk remover gel, if the old bead is silicone
Painter’s tape (blue or delicate-surface tape)
Rubbing alcohol (isopropyl, 70% or higher) and clean rags
Bleach-based cleaner or a mildew remover, plus a nylon scrub brush
Nitrile gloves and safety glasses
A fan or open window for ventilation

Silicone or latex: pick the right caulk

For the joint between a tub or shower pan and the wall, use 100% silicone labeled for kitchens and baths. Silicone stays flexible, sheds water and resists mildew far better than acrylic latex. Its downside is that it is harder to tool and nothing sticks to it, including paint and new caulk. Acrylic latex “siliconized” caulk is easier to work with and cleans up with water, but it shrinks, breaks down faster in a wet zone and usually needs replacing sooner. Save latex for painted trim and dry areas.

One rule matters more than brand: new silicone will not bond to old silicone residue. Every bit of the old bead has to come off.

Step-by-step

Let the area dry out. Skip showers in that bathroom for at least 24 hours before you start, and longer if you can. Caulk applied over a damp joint traps moisture and fails early. Running a fan or a small space heater (kept well away from water) helps.
Cut and pull the old caulk. Score along both edges of the old bead with a utility knife, holding the blade at a low angle so you don’t gouge the tub. On acrylic or fiberglass tubs, use a plastic tool wherever you can. Grab a loose end and pull; much of it will peel off in strips.
Remove the leftovers. Apply caulk remover gel to stubborn silicone, wait the time on the label, then scrape with a plastic tool. Work along the joint until the surfaces feel smooth and not rubbery.
Kill the mildew. Black stains in the joint are mold growing in the gap. Scrub with a mildew cleaner or a diluted bleach solution (follow the label, never mix bleach with ammonia or acidic cleaners) and rinse. Let it dry completely. If the black spots go deep into the grout or the drywall behind the tile feels soft, stop here and read the section on calling a pro.
Wipe with alcohol. Clean both sides of the joint with rubbing alcohol on a lint-free rag. This removes soap film and body oils that keep silicone from sticking. Let it flash off for a few minutes.
Fill the tub with water. A filled tub sits slightly lower, opening the joint to the size it will be when someone is bathing. Caulking in that position means the bead is compressed, not stretched, when the tub is in use. Leave the water in until the caulk has skinned over.
Tape the lines. Run painter’s tape on the wall about 1/8 inch above the joint and on the tub about 1/8 inch below it. This is the secret to a crisp, even bead.
Cut the nozzle small. Snip the tip at a 45-degree angle with an opening just smaller than the gap, usually around 1/8 inch. You can always cut more; you can’t put it back.
Run the bead. Starting in a corner, push the gun along the joint at a steady pace with steady trigger pressure. Pushing (instead of pulling) drives caulk into the gap. Do one wall at a time.
Tool it right away. Smooth the bead with a caulk finishing tool or a fingertip in a nitrile glove, dipped in a little rubbing alcohol or soapy water. Use one smooth pass, wiping excess onto a rag.
Pull the tape while the caulk is wet. Peel it away at a low angle, pulling away from the bead. Waiting until the caulk skins over will tear the edge.
Let it cure. Most silicone is dry to the touch in about 30 minutes but needs around 24 hours before it gets wet. Check the tube; some formulas want longer in cool, humid weather. Drain the tub only after the caulk has firmed up.

Mistakes to avoid

Caulking over old caulk. It looks fine for a few weeks, then peels because the new bead never bonded.
Caulking the tile-to-tile corners with silicone, then grouting. Grout won’t stick to silicone. Inside corners and changes of plane should be caulked, but only after grout is finished and cured.
Using too much. A fat bead is harder to tool, smears onto the tile and traps soap scum. The goal is a thin, slightly concave bead that fills the gap.
Rushing the cure. Showering too early can wash out uncured silicone or leave dimples that collect water.
Skipping ventilation. Removers and some caulks give off strong fumes. Keep a fan running and the door open.

Keep it looking new

Run the exhaust fan during every shower and for 20 minutes afterward. Squeegee the walls and wipe the caulk line once in a while. Most bathrooms need re-caulking every few years; if yours is turning black within months, that usually points to poor ventilation or water already getting behind the tile.

When to call a pro

New caulk is a seal, not a repair. Call a contractor if you notice any of these while the old bead is out:

Tile that sounds hollow, moves when pressed or has cracked grout running up the wall
Soft or crumbling drywall or backer board behind the joint
Water stains or peeling paint on the ceiling below the bathroom
A tub or shower pan that flexes or has visible cracks
Mold that keeps coming back right after cleaning

Those are signs water has been getting into the wall for a while, and the fix may mean opening it up, replacing backer board and resetting tile. That’s the kind of work our kitchen and bath remodeling crew handles, from a single shower surround to a full gut remodel. If the leak has already reached the floor, our flooring team can check the subfloor too.

Rather have it done for you? RossBuilt Construction serves the St. Louis metro. Request a free estimate or call 636-380-2574.