The caulk line where your bathtub meets the wall and floor is the only thing keeping water from getting behind the tub. When it fails, water sneaks into the wall cavity or under the tub deck — and that’s how you end up with rotted subfloors, mold inside the wall, and a repair bill that dwarfs the cost of a $10 tube of caulk. The good news: recaulking a bathtub is one of the easiest homeowner repairs there is.
Total time: 2–3 hours of hands-on work, plus 24 hours of cure time where the tub stays dry.
How to Know Your Tub Needs Recaulking
Don’t recaulk over caulk that’s still doing its job. Look for these signs:
- Cracks or gaps in the bead, even hairline ones. A crack is a direct path for water.
- Peeling or pulling away. If you can lift an edge of the caulk with your fingernail, it’s no longer sealed.
- Black or pink mold that won’t scrub off. Surface mildew on top of caulk cleans off with bleach. Mold inside the caulk — dark staining that stays put after scrubbing — means the caulk has failed and moisture is living in it.
- Missing chunks, especially at the corners where the walls meet or where the tub apron meets the floor.
A typical bathtub caulk job lasts 3–5 years, less in a bathroom with poor ventilation. Check the bead twice a year, the same way you’d check the hoses on a washing machine.
What You Need
Materials
- 100% silicone caulk, kitchen-and-bath formula — one 10-ounce tube is plenty for a standard tub. Get “kitchen and bath” or “mold resistant” on the label. We cover how to pick the right caulk in detail in our companion article on choosing caulk.
- Painter’s tape (blue or green, 1-inch or 1.5-inch width) — for the tape trick that keeps your lines straight.
- Rubbing alcohol (isopropyl, 70% or higher) — for the final wipe-down. Silicone won’t bond to soap scum or residue.
- Paper towels or shop rags.
- Disposable gloves (nitrile) — silicone sticks to skin and doesn’t wash off with soap and water.
Tools
- Caulk gun — a basic dripless caulk gun ($10–15) is fine. Avoid the ratcheting type if you’re a beginner; dripless guns stop the flow when you release the trigger.
- Utility knife with a fresh blade.
- Caulk remover tool or 5-in-1 painter’s tool — the pointed plastic scraper end is designed to get into the seam. A plastic putty knife works too.
- Old toothbrush or small stiff-bristle brush — for scrubbing the seam after the old caulk is out.
- Spray bottle (optional) — mixed with dish soap and water, for smoothing the bead if you use that method.
My pick: I reach for GE Advanced Silicone 2 Kitchen & Bath. It’s 100% silicone, stays flexible, and carries a 10-year mold-free warranty — in my experience it actually holds up. The one I’d steer you away from: cheap latex “siliconized” tubes. They look fine for a year, then they pull away and blacken, and you’re redoing the whole job.
Safety Notes
- Utility knife: Always cut away from your body, and keep your other hand out of the blade’s path. A fresh blade is safer than a dull one — dull blades need more force and slip more easily.
- Ventilation: Silicone caulk releases fumes as it cures. Run the bathroom exhaust fan the whole time, and crack a window if you can.
- Gloves: Silicone bonds to skin quickly and only comes off with mineral spirits or time. Wear nitrile gloves during removal and application.
Step 1: Remove All of the Old Caulk
This is the step people skip, and it’s the step that matters most. New caulk will not bond to old caulk — it needs a clean, bare surface. Leaving even a thin ridge of old material behind gives you a weak seam that fails in a year instead of five.
- Soften it. Score along both edges of the old bead with your utility knife — one pass where the caulk meets the tub, one where it meets the wall. Cut shallow; you’re scoring, not gouging.
- Pull it out. Grab an end with pliers or your (gloved) fingers and pull steadily. Long strips often come out in one piece, which is satisfying and a good sign.
- Scrape the remainder. Use the pointed end of your caulk remover tool or plastic putty knife to dig out whatever’s left in the seam. Work the corners carefully — that’s where most of the residue hides.
- Scrub the seam. Hit the bare seam with the stiff brush and a bathroom cleaner or a vinegar-and-water mix to remove soap scum, mildew, and mineral buildup.
- Wipe with rubbing alcohol. Dampen a rag with rubbing alcohol and wipe the full length of the seam, both surfaces. This removes the last invisible film of soap and body oil. Let it dry completely — the seam must be bone dry before you apply new caulk. Give it 15–30 minutes after wiping.
Plan on 60–90 minutes for this step alone on a tub that hasn’t been recaulked in years. It’s tedious. Do it anyway.
Step 2: Tape the Seam
The painter’s tape trick is what separates a pro-looking job from a wavy mess, especially for beginners.
- Run a strip of painter’s tape along the tub, about 1/4 inch from the seam, following the contour of the joint.
- Run a second strip on the wall (or the tub apron, for the floor joint), also about 1/4 inch from the seam.
- You now have a narrow channel between two tape lines — about 1/2 inch wide. That’s where your caulk bead will go.
- Tape the inside corners too. Where the wall meets the wall at the tub ends, run short pieces of tape to square off the corner.
Press the tape edges down firmly. Caulk that seeps under a lifted tape edge is the one common way this trick backfires.
Step 3: Prep the Tube
- Cut the tip of the caulk tube nozzle with your utility knife. Cut at a 45-degree angle, and start small — cut off just the tip. You want a hole roughly 1/8 to 3/16 inch across. You can always cut it bigger; you can’t cut it smaller.
- Poke the inner foil seal. Most tubes have a foil seal inside the nozzle. Use a long nail, a wire, or the puncture pin built into many caulk guns to break it.
- Load the tube into the caulk gun, nozzle end first, and squeeze the trigger until caulk just starts to show at the tip.
The size of the nozzle opening controls the size of your bead. For a tub seam, the opening should be slightly smaller than the gap you’re filling — the bead widens as you smooth it.
Step 4: Apply the Caulk
- Start in the back corner of the tub and work toward yourself. Hold the gun at about a 45-degree angle to the seam, nozzle pressed lightly into the joint.
- Squeeze steadily and move at a consistent speed. The goal is a continuous, unbroken bead that fills the channel between your tape lines. Moving too fast gives you a thin, starved bead with gaps; moving too slow gives you a fat bead that makes a mess when you smooth it.
- Do one seam at a time. Caulk starts to skin over in 10–15 minutes, and you can’t smooth it after that. Finish each straight run (back wall, side wall, front apron) before moving on.
- If you need to stop mid-bead, press the release lever on the caulk gun (dripless guns do this automatically) and overlap your restart point by an inch or so.
Don’t worry if the bead looks rough at this stage. The smoothing step is where it gets its finish.
Step 5: Smooth the Bead
This is the step that determines how the finished job looks.
- Wet your finger (gloved) with water or a drop of dish soap and water. Or use a damp paper towel folded into a pad.
- Run your finger along the bead in one smooth, continuous pass, pressing lightly. This forces the caulk into the joint and gives it the classic concave profile.
- Wipe the excess off your finger as you go. On long runs, you may need to re-wet and do a second pass — but keep it to two passes max. Overworking silicone after it starts to skin gives you a lumpy, draggy finish.
- Immediately pull the tape while the caulk is still wet. Pull slowly, at a low angle away from the bead. Pulling tape after the caulk skins will tear the edge.
My method, once you’re comfortable: skip the tape. Cut the nozzle small at 45°, lay the bead, and tool it with a wet finger in one continuous pass — a drop of dish soap in the water keeps the silicone from sticking to your skin. On corners, tool into the corner rather than globbing extra caulk in. And wipe up with a damp rag, not paper towels — paper towels shed fibers right into the bead.
Step 6: Let It Cure — 24 Hours Minimum
- Do not touch the bead once the tape is off. Walk away.
- Keep the tub dry for 24 hours. No showers, no splashing. Plan the job for a day when you can use a second bathroom, or shower the night before and recaulk the next morning.
- Leave the exhaust fan running or the bathroom door open for airflow. Silicone cures by reacting with moisture in the air, but standing water on the bead before it cures will ruin the finish.
- After 24 hours, check the bead. It should be firm and rubbery with no tackiness. If the bathroom is cold (below 50°F), give it a full 48 hours.
The mistake I see most: skipping the cleaning. People lay fresh caulk over soap scum, mildew, or a ridge of old caulk instead of stripping the joint down to a clean, bare surface first — then wonder why it peels in six months. Silicone only bonds to clean. Runner-up: using the shower the same night. The tube says “water-ready in 30 minutes,” but a full cure is 24 hours.
Clean Up
- Wipe down your tools with a dry rag before the caulk cures on them. Uncured silicone wipes off; cured silicone needs a razor.
- Cap the tube (a nail or screw in the nozzle, wrapped with tape) and store it upright. An opened tube of silicone lasts a few weeks if sealed well.
- Toss the tape, gloves, and old caulk in the trash — not the drain.
FAQ
Can I caulk over old caulk?
No. New silicone caulk does not bond to old caulk. It needs a clean, bare surface to grip. Caulking over old caulk gives you a seam that looks fine for a few months and then peels off in strips. Take the hour to remove the old material — it’s the highest-leverage part of this job.
Should I use silicone or latex caulk in a bathtub?
Use 100% silicone, kitchen-and-bath formula. Latex (paintable) caulk is easier to apply and clean up, but it shrinks as it dries, cracks sooner, and isn’t as waterproof. Silicone is harder to work with and impossible to paint over, but in a wet zone like a tub, it’s the right material. For the full breakdown of caulk types, see our companion article on choosing caulk.
How long does bathtub caulk last?
Typically 3–5 years with decent bathroom ventilation. If your bathroom has no exhaust fan or you take long, steamy showers with the door closed, expect closer to 2–3 years. Inspect the bead twice a year and recaulk at the first sign of cracking or peeling — catching it early keeps it a one-afternoon job.
Why is my new caulk bead lumpy?
Almost always one of two causes: the nozzle was cut too big (giving you too much caulk to smooth), or the bead was overworked after it started to skin over. Cut the nozzle smaller than you think you need, smooth each run in one or two continuous passes, and pull the tape while the caulk is still wet.
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