Replacing cracked, moldy caulk around the tub and sink
Caulk that is cracked, peeling or stained with mildew should be fully removed, the joint cleaned and dried, and new mildew-resistant silicone applied. Caulking over old caulk traps moisture and fails quickly. Let it cure for a full day before running water on it.
Caulk is the flexible seal where your tub meets the tile, where the sink meets the counter, and around the base of the toilet. It is supposed to keep water out of the joints. In busy Rosemead households, a shower can run several times a day, and caulk takes a beating.
Our process
- Cut and scrape out all old caulk.
- Remove residue with a solvent made for the type of caulk.
- Clean with a mildew remover and let the joint dry completely.
- Fill the tub with water, which weighs it down and opens the joint to its widest.
- Apply mildew-resistant silicone and tool it smooth.
- Leave it to cure before using the shower.
Grout versus caulk
Grout fills the joints between tiles. Caulk goes in corners and changes of plane, where things move. If the grout is cracked, it may need regrouting rather than caulk.
Signs it is time
Caulk around tubs, showers, sinks and countertops wears out. It cracks, shrinks, turns black with mildew, or peels away from one side. Once there is a gap, water gets behind it, into the wall, under the tub, or into the vanity.
In Rosemead homes with slab floors, water that gets under a tub can sit unseen for a long time. A fingernail test helps: if you can push a nail behind the caulk, it has lost its bond.
Caulk types
- 100 percent silicone: the most water-resistant and flexible, best for tubs and showers. It cannot be painted, and new silicone does not stick to old silicone.
- Siliconized acrylic: easier to tool and clean with water, paintable, but shorter-lived in wet areas.
- Kitchen and bath acrylic with mildewcide: fine for vanity backsplashes and trim, less durable in showers.
- Hybrid polymer sealants: strong and paintable, good where caulk meets different materials.
Choose a color that matches the grout or fixture. White, almond, bone and clear are common.
Removing old caulk
Old caulk must come out completely. Slice the caulk free on each side with a razor or plastic caulk remover, then pull it out and scrape off the rest. Caulk softener or remover helps with stubborn acrylic.
Silicone residue needs mineral spirits or a silicone remover; new silicone will not bond over residue. Be careful on acrylic tubs and cultured marble, which scratch easily.
Treating mold
Black spots under old caulk are mold. After removing the caulk, scrub with a cleaner made for mold or a diluted bleach mix, rinse, and let it dry completely. Run a fan or leave the bathroom door open overnight. Caulking over damp joints traps moisture and the mold comes back.
Our steps:
- Remove old caulk and residue
- Clean and treat mold, then rinse
- Dry the joint completely
- Fill the tub with water to load the joint
- Mask the joint with painter's tape on each side
- Run one even bead and smooth it with a tool or fingertip
- Remove tape while wet and let it cure
Sinks and countertops
The joint where a vanity top meets the wall, and around an undermount sink, also needs caulk. Kitchen backsplashes need a bead along the counter to keep spills out of the wall. Around a sink rim, caulk keeps water from wicking under the edge and swelling the cabinet.
Curing time
Silicone usually needs 24 hours before water exposure. Some fast-cure products allow use in a few hours; read the label. Leave the tub filled with water until the caulk cures.
When caulk is not enough
If tiles are loose, grout is crumbling, or the wall feels soft, caulking alone will not fix it. Those need tile and wall repair. See under-sink leaks and supply lines for problems under the vanity, and hard water buildup for mineral deposits around fixtures.
Keeping it clean
Squeegee showers after use, run the bathroom fan for 20 minutes after bathing, and wipe the caulk joint with a mild cleaner weekly. Good ventilation slows mildew a lot.
Around fixtures
Caulk around faucet bases, tub spouts and shower trim plates keeps water out of the wall. Leave a small weep gap at the bottom of shower trim plates so water that gets behind can drain.
Color and finish
Clear silicone shows mold behind it once it ages. White or matching colors hide dirt better. Smooth tooling leaves fewer ridges where dirt collects. Wiping with a damp cloth after showers keeps it bright.
Tools
A good caulk gun with a smooth trigger gives a steady bead. Dripless guns stop flow when you release the trigger. A tooling tool or a plastic spoon leaves a smooth concave bead.
Keep paper towels and a trash bag nearby. Cut the nozzle at an angle, slightly smaller than the joint.
Plan the job for a time when nobody needs the shower for a full day, so the caulk can cure fully before it gets wet.
Recaulking we do
Tub, shower, sink and toilet joints are all jobs we strip and redo, along with touching up any paint the old caulk damaged. See minor plumbing.
When you want it done for you, our plumbing repairs page lists the jobs we take and what to send for a quote. More on the houses themselves: repair notes for postwar Rosemead homes.
Need a hand with this?
Call or text (310) 628-9399, Mon–Sat 8:30 AM–7 PM. A photo is usually enough for a free estimate.
Call or text for a free estimate