Sooner or later, mold always shows up in bathroom caulking. This article explains how to clean the old caulk out and then recaulk around a shower or tub.
By the DIY experts of The Family Handyman Magazine
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Anybody can caulk a shower or tub. All you need is a tube of caulk and a caulking gun. But if you don’t prep the surfaces properly, the caulk won’t last long. And if you’re sloppy, the messy caulk job will ruin the look of even the most beautiful tile job. We talked to a few experts to learn how they get such smooth, clean-looking caulk lines, and we’ll show you their technique. And we’ll show you the best way how to remove mold from shower caulking and prep the surface to get a long-lasting caulk job. Finally, we’ll give you a heads-up on how to avoid the most common caulking mistakes.
Watch this video to learn how to caulk your shower or bathtub the right way:
You can remove the old caulk, prep the surface, and recaulk a tub or shower in about four hours (including drying time). You’ll need a razor scraper and single-edge razor blades, caulk remover, mineral spirits, paper towels, a utility knife, a caulk gun, and kitchen and bath caulk. An oscillating tool with a flexible scraper blade really speeds up the job of removing old caulk, but you can do the job without it. Here’s how to start.
Buy the right caulk and a quality caulk gun
Tubs and showers require a special caulk that contains mold and mildew prevention additives. The tubes are usually labeled “for kitchen and bath use.” Most are 100 percent silicone, but you can also find some latex versions. Latex caulk is easier to tool and cleans up with soap and water. If this is your first time applying caulk, latex may be your best option. Silicone is more challenging to tool and requires mineral spirits for cleanup. However, silicone lasts longer than latex and stays flexible over its life. But it’s harder to remove when it’s time to recaulk. Both types can develop mold and mildew once the additives wear out.
Most home centers and hardware stores stock only three kitchen and bath caulk colors: white, almond and clear. However, ask a salesclerk whether you can special-order a custom color. And check out a paint or hardware store. Some can custom-mix colors right in the store. Most tile stores will carry a full range of colors.
A high-quality caulk gun can make a difference in your caulk job. It has a sturdier plunger mechanism to provide a smooth, even flow and a pressure release to stop the flow quickly. High-quality caulk guns cost a bit more (about $15), but they’re worth it. Economy guns usually have a ratchet action or a sloppy friction mechanism that pushes the caulk out in bursts, so you apply too much in some areas and too little in others.
Preparation: Remove the old caulk
Photo 1: Cut and peel the old caulk
Slice through the caulk along the walls with a utility knife or with an oscillating tool equipped with a flexible scraper blade. Then use your knife or tool to scrape along the tub or shower floor.
Photo 2: Loosen and remove the remaining caulk.
Squirt caulk remover on all the remaining caulk and let it do the hard work. Then scrape off all the old caulk with a razor scraper. Wipe with a rag.
You can’t apply new caulk on top of the old and expect it to last. So the old caulk has to go. If the old caulk was silicone, you have to devote extra effort to remove all traces of it before applying new caulk. Start by slicing through the old caulk with a utility knife or an oscillating tool (Photo 1). Then scrape off as much old caulk as possible. Next, apply caulk remover to break the adhesive bond and make it easier to scrape off (Photo 2).
Once the old caulk is gone, remove any loose grout between the walls and the tub or shower floor. Treat any mold in the grout along the wall/tub gap with a mold-killing product. Scrub the grout and then rinse off the mold killer with water and let it dry (use a hair dryer to speed the drying). Clean the surfaces one last time with mineral spirits. Let dry.
How to Caulk a Shower or Tub: Mask the gap
Photo 3: Mask the gap
Mask the wall corner gaps first. Then apply tape to the walls above the tub or shower floor. Finish by applying tape to the tub or shower floor.
Some pros scoff at the idea of using masking tape. But they caulk every day and can lay down a caulk bead with their eyes closed. For DIYers, we recommend masking the gap. It takes a bit more time, but you’ll get much better results than caulking freehand. Start by finding the largest gap between the tub/shower and the walls. That gap dictates how far apart you must space the two rows of tape. Then apply the masking tape (Photo 3). If you have a fiberglass or composite tub, you should fill it before you caulk.
Avoid These Caulking Mistakes
Buying the wrong caulk. Always use kitchen and bath caulk in a tub or shower. It contains mold and mildew inhibitors that are not present in other types of caulk.
Caulking on top of old caulk. New caulk doesn’t bond well to old caulk, especially if the old caulk contains silicone. Just like with painting, better surface prep provides better results.
Not removing mold on grout near the caulk areas. Grout is porous, and any mold present in the grout above the caulk line will eventually spread down into the new caulk area and destroy the bond.
Cutting the nozzle larger than the gap you’re filling. A larger opening applies too much product, making it harder to tool and clean up.
How to Caulk: Apply the caulk bead
Photo 4: Cut, push and apply
Cut the nozzle tip to match the gap width. Hold the gun at a 90-degree angle to the gap and push a bead of caulk slightly ahead of the nozzle as you push the gun forward and continue applying pressure. Apply only enough caulk to fill the gap.
There are two schools of thought when it comes to tip angle and whether to pull or push the caulk. Our experts prefer cutting the caulk tube nozzle at a blunt 20-degree angle, instead of 45 degrees. And they hold the gun at a 90-degree angle to the gap while pushing a small bead ahead of the tip (Photo 4). That way, they can complete the entire bead in one pass. Plus, the gun pressure forces the caulk deeper into the gap for better holding power and sealing.
If you cut the tip at a 45-degree angle and pull the gun away from the starting corner, your gun will always run into the opposite corner, forcing you to flip it 180 degrees and start the bead again. That creates a blob where the two beads meet, making tooling more difficult. Plus, pulling the gun tends to apply a surface bead that doesn’t penetrate as far into the gap.
Whichever tip angle you choose, always cut the tip with a sharp utility knife rather than the cheesy guillotine mechanism built into some caulk guns. Remove any burrs with a utility knife or sandpaper before caulking—the burrs will create grooves in the caulk lines.
How to Caulk: Shape the bead and remove the tape
Photo 5: Tool with your finger
Wet your finger with water and start at an outer corner. Wipe your finger across the caulk to create a rounded bead and remove excess caulk from the gap.
Photo 6: Peel off the tape
Lift a corner of the tape along the tub and pull it off at a steep angle while the caulk is still wet. Then remove the tape along the wall. Remove the tape from the wall corners last.
You can find all kinds of caulk-shaping tools at home centers. But if you take our advice and tape off the wall, you won’t need any shaping tools. Just use your index finger to tool the caulk (Photo 5). After tooling, remove the masking tape while the caulk is still wet (Photo 6). Let the caulk cure for the recommended time before using the tub or shower.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
You’ll also need a razor scraper, single-edge razor blades and an oscillating tool.
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.