Updated July 5, 2026 · 7 min read
Caulk is the only thing standing between shower water and the framing behind your tub or tile — and unlike the tile, it is a wear part. It is designed to be removed and replaced periodically, and a failed caulk joint is one of the most common ways water quietly gets into walls and floors.
This guide covers the maintenance cycle: how to recognize caulk that is done, the honest trade-offs between silicone and acrylic latex, how to strip the old bead properly (the step most DIY jobs skimp on), and how to keep mildew from colonizing the new one.
One scope note: caulk failure and bathroom mold are both moisture stories, and half of moisture control is air movement — running the fan, drying the room. That side is covered in our bathroom ventilation tips; this guide stays on the joint itself.
Key takeaways
- Re-caulk on any of the three signs — discoloration that will not clean off, cracks, or separation. A visibly failed bead is already letting water into the wall.
- Silicone is the wet-area performance pick (waterproof, flexible, long-lived, but unpaintable and hard to redo); acrylic latex tub-and-tile caulk is easier to apply and replace but comes due sooner.
- Removal is the job: strip the old bead completely, deal with silicone residue, clean with alcohol, and let the joint dry at least 30 minutes before new caulk.
- Application discipline — 45-degree cuts, taped lines, one continuous pass, immediate tooling — is what separates a five-year bead from a five-month one.
- Give new caulk 30 minutes before water and 24 hours before use, then protect it the same way you protect grout: ventilation and quick moisture cleanup.
When to re-caulk: the three signs
Bob Vila’s test for replacement is simple — caulk is due when it is discolored, has developed cracks, or has begun to separate from the surfaces it seals. Any one of the three is enough: discoloration that will not clean off usually means mildew has grown into (not just on) the bead, cracks let water past even when the bead looks attached, and separation is an open channel to the wall cavity.
A gap you can see is a leak you cannot. Water that gets behind a tub flange or under a shower curb does its damage invisibly — which is why re-caulking on the early signs is one of the cheapest pieces of preventive maintenance in the house, and why "it still mostly looks fine" is not the standard to use in a shower.
Silicone vs. acrylic latex: the honest trade-offs
Tub-and-shower caulks come in two chemistries, and both are sold in "Tub and Tile" or "Kitchen and Bath" formulations chemically designed to resist mildew and stick to smooth, nonporous surfaces, per This Old House.
Silicone is the durability pick. Per Bob Vila, pure silicone is more waterproof and flexible, better resists rot, rarely cracks with thermal expansion, and lasts decades — which is why Bob Vila recommends pure silicone specifically for showers and tubs. The costs: it is unpaintable, harder to tool smoothly, needs mineral spirits for cleanup, and — as This Old House notes — it leaves a residue that almost nothing, including fresh silicone, sticks to, which makes the eventual replacement job harder.
Acrylic latex is the workability pick. It tools easily, cleans up with water, has little odor, and is simple to remove and replace — the reason This Old House Magazine recommends acrylic latex for tub jobs is precisely that it will be easier to replace than silicone when the time comes. The trade: it is less moisture-resistant and more likely to crack with temperature swings, so the joint comes due sooner.
| Factor | Pure silicone | Acrylic latex (tub & tile) |
|---|---|---|
| Water resistance | Excellent — the wet-area benchmark | Good, but less moisture-resistant |
| Flexibility / cracking | Rarely cracks with thermal movement | More prone to cracking over time |
| Ease of application | Sticky, unforgiving to tool | Easy to smooth and correct |
| Cleanup | Mineral spirits | Water |
| Paintable | No | Yes |
| Future replacement | Harder — residue resists new caulk | Easier to strip and redo |
Trade-offs per Bob Vila and This Old House. Both chemistries must be a "Tub and Tile" / "Kitchen and Bath" formulation with mildewcide for wet areas.
Which should you actually buy?
For the wettest joints — shower corners, the tub-to-tile line, the enclosure-to-pan seam — silicone’s moisture performance is why Bob Vila recommends it there. If you know you will be the one redoing the joint and want a forgiving material, quality tub-and-tile acrylic latex is a legitimate choice This Old House endorses; just expect a shorter cycle. Do not use plain painter’s caulk in a shower — wet-area formulation is non-negotiable.
Removing the old caulk — the step that decides the job
New caulk over old caulk fails early, and fresh silicone will not bond to old silicone residue — so removal is the real work. This Old House’s method: cut the old bead away with a razor scraper or utility knife held at a low angle; for stubborn silicone, slice down the middle of the bead and pull it out with needle-nose pliers.
For beads that will not cut cleanly, Bob Vila describes chemical caulk removers that soften (not dissolve) the bead — give them at least four hours to work, and longer is better. A hair dryer or heat gun softens persistent sections, and alcohol-soaked rags left on silicone residue for an extended period break down what scraping leaves behind. Identify what you are removing first: silicone is rubbery and stretches, water-based caulk is harder and chips — remover products are formulated for one or the other.
Once the joint is bare, clean it with rubbing alcohol and let it air-dry — This Old House calls for at least 30 minutes — before the new bead goes in. Caulk over damp or soap-filmed surfaces and you have scheduled the next failure.
Laying a bead that lasts
- Cut the tube nozzle at 45 degrees, about 3/16-inch opening, per This Old House.
- Tape both sides of the joint with painter’s tape roughly 3/8-inch apart for a crisp, even line.
- Hold the gun at 45 degrees and keep steady pressure and steady movement — one continuous pass beats stop-start dabs.
- Tool the bead with a damp, lint-free rag (or a fingertip) in one smooth pass, using light pressure.
- Pull the tape immediately, at a 45-degree angle, before the caulk skins over.
- Give it 30+ minutes before any water exposure and 24 hours before using the tub or shower, per This Old House.
Keeping mildew off the new bead
Tub-and-tile caulks are formulated with mildewcides, but no additive outlasts a permanently damp bathroom. The bead stays clean the same way grout and glass do: move the moisture out. Run the exhaust fan during and well after showers, leave the door or curtain open so the joint dries, and wipe standing water off horizontal caulk lines (tub decks, curbs, shelf joints) where it pools longest.
When surface mildew does appear, clean it early with a bathroom cleaner and soft brush — established staining grows into the bead, and per Bob Vila, discoloration that will not clean off means the bead is due for replacement, not more scrubbing. If a joint keeps molding fast no matter what, treat that as a moisture symptom: check the fan actually moves air (our ventilation tips include the toilet-paper test) and make sure water is not sitting behind the joint — recurring failure in one spot can point to a waterproofing problem rather than a caulk problem.
Frequently asked questions
- How do I know when it is time to re-caulk a tub or shower?
- Per Bob Vila: when the caulk is discolored, cracked, or separating from the tub or tile. Any one sign is enough — discoloration that will not clean off means mildew has grown into the bead, and cracks or gaps are letting water behind the wall even if the joint mostly looks intact.
- Is silicone or latex caulk better for a shower?
- Silicone performs better in the wettest joints — Bob Vila recommends pure silicone for showers and tubs because it is more waterproof, stays flexible, and rarely cracks. The trade-off is that it is harder to apply and harder to replace, since new caulk will not stick to silicone residue. This Old House Magazine makes the case for tub-and-tile acrylic latex on replaceability grounds: it is easier to tool and far easier to strip and redo. Either way, use a "Tub and Tile" or "Kitchen and Bath" formulation with mildewcide.
- Can I just caulk over the old caulk?
- No — new caulk bonded to a failing bead fails with it, and fresh silicone will not adhere to old silicone residue at all. Strip the old bead completely (razor scraper, pliers for silicone, chemical remover or heat for stubborn sections), clean the joint with rubbing alcohol, and let it dry at least 30 minutes before applying the new bead, per This Old House.
Sources
- This Old House — How To Caulk a Bathtub
- Bob Vila — The Best Caulk for Showers, Tested
- Bob Vila — How to Remove Caulk
Claims and figures are drawn from the sources above and provided for general guidance; your project may vary. Photography is illustrative of design concepts. For a fixed price on your specific bathroom, request a free estimate.
