How to Caulk a Bathtub or Shower So It Lasts

Look for gaps where the caulk has pulled away from the tub or tile, cracks along the line, sections that are peeling, and black or pink spots that will not scrub off. Dark spots under the surface usually mean mold has grown into or behind the caulk, and cleaning will not fix it.

Other warning signs are loose tiles near the tub, grout that is crumbling at the bottom row, or a soft spot in the floor next to the tub. Those point to water already getting in, so caulking should happen soon, and the area should be checked for damage.

Tubs move. A tub filled with water and a person flexes slightly, and the joint opens and closes over time. Caulk that is too stiff, too thin, or not stuck to a clean surface cracks under that movement.

The most common cause of early failure is caulking over old caulk or soap scum. New caulk does not bond well to old silicone or residue, so it peels within months. Using the wrong product, such as a painter's caulk meant for dry trim, is the second most common cause.

Moisture is the third. Caulk needs a dry surface and time to cure. Showering before it cures, or laying it over a damp joint, weakens the bond from day one.

For tubs and showers, use a caulk labeled for kitchen and bath use with mold and mildew resistance. 100 percent silicone is the most common choice because it stays flexible and waterproof for years. It is a little harder to work with and cannot be painted, but in a wet area that rarely matters.

Siliconized acrylic or hybrid caulks are easier to tool and clean up with water, which makes them friendlier for beginners, though they may not last as long in constant wet. Pick a color that matches the grout or tub, usually white, almond, or clear, and read the label for cure time before the tub can be used.

This step decides how long the new caulk lasts. Use a plastic scraper or a utility knife held at a low angle to cut and peel the old bead out. A caulk removal tool helps in corners. Go slowly on acrylic or fiberglass tubs so you do not scratch the surface.

Silicone leaves a thin film behind. Remove it with a caulk remover product or rubbing alcohol and a plastic scrubber until the surface feels clean, not slick. If there is mold in the joint, clean it with a bathroom mold cleaner and rinse well.

Then let the joint dry completely. In most bathrooms that means at least several hours, and overnight is better. Running a fan helps. The joint must be dry before you caulk.

Run strips of painter's tape along both sides of the joint, leaving a gap about the width you want for the bead. Tape is the simplest way to get a straight, professional-looking line.

Here is a tip many pros use: fill the tub with water before you caulk. The weight pulls the tub down to its lowest position, so the caulk cures in the widened gap and does not get stretched later when someone takes a bath. Drain it only after the caulk has cured.

Cut the tip of the tube at a small angle so the opening is a little smaller than the gap. Work in one smooth pass along each wall, pushing the caulk into the joint rather than dragging it on top.

Smooth the bead right away with a caulk tool or a fingertip dipped in soapy water (for silicone) or plain water (for acrylic). Press lightly so the caulk fills the gap and forms a slight curve. Pull the tape off while the caulk is still wet, pulling away from the bead at an angle.

Leave the shower unused for the full cure time on the label, often 24 hours, and keep the bathroom ventilated. Resist touching it to check.

After every shower, run the fan or crack a window, and squeegee the walls if you can. Mold grows where water sits. Clean the caulk line with a gentle bathroom cleaner once a week. Most well-done caulk jobs last several years before they need to be redone.

If you would rather have it done right the first time, a pro recaulk of a standard tub or shower typically costs somewhere around $150 to $400, depending on how much old caulk and mold has to come out. Handmax recaulks tubs and showers across the San Diego area. Text a photo of the joint for a free quote, and if the photo shows loose tile or soft drywall, we will tell you that too.