Caulk Around a Bathtub to Stop Edge Leaks

Black dots in the old bead, a soft spot when you press the joint, or a faint musty smell after showers — that is failed tub caulk. Water sits in the gap and works into the wall cavity. Recaulking will not fix a rotten subfloor, but it stops the everyday splash path.

Use 100% silicone labeled for kitchen/bath (mildew-resistant). Acrylic “painter’s caulk” alone is the wrong product for a constantly wet tub rim.

Strip the old bead clean

1. Score both edges of the old caulk with a sharp utility knife. Keep the blade shallow so you do not gouge acrylic tubs.
2. Pull or scrape the bead out. A plastic caulk-removal tool helps on long runs.
3. Dig crumbs out of the corner. Vacuum or wipe debris.
4. Wipe the joint with rubbing alcohol. Let it fully dry — silicone hates damp joints. After a shower, wait overnight if the gap still feels cool and wet.

If you find soft drywall, dark wet sheathing, or the tub rim moves independently from the wall, stop. That is damage beyond a cosmetic bead.

Tape for a clean line (optional but worth it)

Painter’s tape on the tub deck and on the tile, leaving a narrow channel for the bead, makes amateur work look intentional. Pull tape while silicone is still wet.

Lay the bead

1. Cut the nozzle at a 45° angle — small opening first; you can enlarge.
2. Gun a continuous bead into the joint. Steady pressure beats start-stop blobs.
3. Tool with a wet finger or a caulk finishing tool in one pass. Do not overwork it into smears.
4. Remove tape. Check for holidays (gaps) and touch sparingly.

Cure time: often 24 hours before soaking showers — read your tube. A quick wipe-down rinse is not the same as a hot steam shower against fresh silicone.

Mistakes that fail in a month

• Caulking over mildew without killing and drying the joint.
• Using latex caulk “because it cleans with water.”
• Leaving old silicone underneath so the new bead bonds to garbage.
• Filling a huge gap with caulk alone — backer rod belongs in wide joints; oversized gaps may need a remodeler.

When to stop

Stop if the tub surround flexes, tiles sound hollow from water damage, or you see active leaks in the ceiling below. Recaulking a doomed wall wastes a weekend.

FAQ

Clear or white silicone?

Match the look you already have. Clear shows dirt differently; white hides slight irregularities on white tubs.

Can I caulk over old caulk?

Only if the old layer is thin, bonded, and clean — usually worse than stripping. Strip when in doubt.

How often redo it?

When it cracks, peels, or grows mildew you cannot clean. Many baths need attention every few years depending on ventilation.