How Do I Recaulk a Bathtub?

Caulk is the flexible waterproof seal where your bathtub meets the wall and floor. When it cracks, peels, or turns black with mold, water seeps behind the tub every time you shower — silently rotting the wall and subfloor. Recaulking is one of the highest-value DIY jobs in a home: about $15 in materials, an afternoon of work, and it prevents thousands of dollars in water damage.

Signs your bathtub caulk needs replacing

• Cracks, gaps, or sections pulling away from the tub or tile
• Black, brown, or pink discoloration that scrubbing will not remove (mold growing inside the caulk, not on it)
• Caulk that feels mushy or crumbly instead of firm and rubbery
• Water pooling in the gap between tub and wall after a shower
• A musty smell near the tub with no visible leak

If the caulk is under 2 years old and just surface-stained, try scrubbing with a bleach-based bathroom cleaner first. But mold inside the caulk cannot be cleaned — the caulk has to go.

What you will need

• 100% silicone caulk, kitchen & bath rated (1–2 tubes, white or matching color)
• Caulk gun (a dripless model is worth the extra few dollars)
• Caulk remover tool or plastic putty knife (avoid metal on fiberglass tubs)
• Utility knife with fresh blade
• Rubbing alcohol or denatured alcohol
• Painter’s tape (1-inch)
• Spray bottle with dish soap + water
• Rags, paper towels, and nitrile gloves

About caulk choice: use 100% silicone, not latex/silicone blends, for a bathtub. Silicone stays flexible for 10+ years, resists mold better, and bonds to tile and tub surfaces. Latex caulk shrinks, cracks sooner, and fails in constant-wet areas. “Kitchen & bath” labeling means it has mildewcide added — worth having.

Step 1: Remove ALL the old caulk

This is the step people rush, and it is the reason recaulking jobs fail. New caulk will not bond to old caulk residue.

1. Soften it. Apply a caulk remover gel (or just score it) and wait 30–60 minutes. Heat from a hair dryer also softens silicone.
2. Cut both edges. Run a utility knife along where the caulk meets the tub AND where it meets the tile, so you are cutting it free on both sides.
3. Pull and scrape. Use the caulk remover tool or plastic putty knife to pull the bead out in strips. Get into the corners.
4. Remove every trace. Rub the joint with a rag soaked in rubbing alcohol to dissolve the thin silicone film that remains. New silicone does not stick to old silicone — this film is the #1 cause of premature failure.
5. Let it dry completely. The joint must be bone-dry before recaulking. Wait several hours, or overnight if you can.

Step 2: Tape the joint

Perfect-looking caulk lines are not a steady hand — they are tape.

1. Run two parallel strips of painter’s tape: one on the tub, one on the wall/tile, leaving about a 1/4-inch gap between them where the caulk will go.
2. Press the tape edges down firmly so caulk cannot bleed underneath.
3. The gap width determines your bead size — 1/4 inch is standard for a tub.

Step 3: Fill the tub with water

This is the trick most tutorials skip: fill the bathtub with water before caulking. A full tub weighs hundreds of pounds and pulls the tub down slightly, opening the joint to its widest. If you caulk with the tub empty and it flexes down later, the fresh caulk stretches and cracks. Keep the water in until the caulk cures (usually 24 hours).

Step 4: Apply the new caulk

1. Cut the tube tip at a 45° angle, opening about 1/4 inch (match your taped gap). Pierce the inner seal.
2. Load the caulk gun and squeeze until caulk reaches the tip, then release pressure (dripless guns handle this automatically).
3. Lay one continuous bead along the joint, moving at a steady pace. Keep the gun at 45° and push the bead ahead of the tip rather than dragging it behind — pushing forces caulk into the joint.
4. Do not stop mid-side. If you run out, overlap the new bead onto the old one slightly.

Step 5: Tool the bead and pull the tape

1. Wet your finger (or a caulk finishing tool) in the soapy water spray and run it along the bead in one smooth pass to press it into the joint and create the classic concave profile.
2. Pull the tape immediately — while the caulk is still wet — pulling outward at a 45° angle. Waiting lets the caulk skin over and tear when you pull tape.
3. Do one cleanup pass with a damp finger along any rough spots. You get one shot; re-touching after it skins makes it worse.
4. Let it cure. Leave the tub full and untouched for 24 hours (check the tube — some silicones need 48). No showers.

What this costs

Mistakes to avoid

• Caulking over old caulk. New silicone over old silicone peels within months. Remove it all.
• Using latex caulk in the tub. It shrinks and cracks in wet areas. Silicone only.
• Skipping the water-in-tub step. Tub flex is a leading cause of fresh caulk cracking.
• Pulling tape after the caulk skins. Pull it while wet, within minutes.
• Showering the same day. Uncured caulk washes out of the joint. Wait the full cure time.
• Caulking the weep holes. Some tubs have small drainage gaps at the bottom of the surround — do not seal those; they let trapped moisture escape.

Frequently asked questions

How long does bathtub caulk last? Good 100% silicone caulk lasts 10–20 years if the surface was prepped properly. Poor prep or latex caulk fails in 1–3 years.

Can I just caulk over the old caulk? No — this is the most common recaulking mistake. New caulk does not bond to old caulk, and the trapped mold underneath keeps growing. Remove it completely.

Why is my new caulk already cracking? Usually one of three causes: old caulk residue left underneath, the tub was not filled with water during application, or latex caulk was used instead of silicone.

Silicone vs. latex caulk for a bathtub? Silicone, every time. It stays flexible, resists mold, and lasts years longer in constant moisture. Latex is easier to apply and paint over, but it does not belong in a tub joint.

When to call a pro

• The wall behind the caulk is soft, crumbly, or discolored — water has already gotten in and there may be rot or mold inside the wall that needs opening up.
• The tub itself moves or rocks — a structural issue no caulk can fix.
• You find black mold covering a large area behind the removed caulk — a remediation pro is safer than DIY for extensive mold.
• You are recaulking and the same joint keeps failing — a tile contractor can check whether the tub was set correctly in the first place.