How to Caulk a Bathtub Large Gap

Do you need to to caulk a bathtub wide gap? Have you noticed moisture or mold in your bathroom? Well, it’s pretty straightforward! You can easily seal large gaps between the tub and the wall with caulk.

Caulk is waterproof and so it would keep moisture out of the space. If you’ve been seeing mold and moisture in your bathroom, it is probably because you have to re-caulk the bathtub wide gap.

You can protect your home and safe money on extensive repairs by simply following these instructions in this article. Caulking is usually easy for most homeowners, even during their first try, so it should be easy for you.

4 Steps to Caulk a Bathtub Wide Gap:

Tools Needed:

  • Chemical caulk remover.
  • Needle-nose pliers.
  • Rubbing alcohol.
  • Caulk removal tool.
  • Putty knife.
  • Cleaning napkins.

Step 1: Spread the Chemical Caulk Remover

Spread over the chemical caulk remover on the old caulk, which would make it easier for you to get rid of the old caulk by softening it. You can purchase the chemical in a hardware store where you get the new caulk.

Step 2: Create a Grip

Next, create a grip by shifting a small section of the caulk with the caulk removal tool. You can also use the putty knife. Ensure that you are shifting the caulk away from the wall.

Step 3: Remove the Caulk Section by Section

Then, remove sections of the caulk with the needle-nose plier. You might have to keep creating a grip and removing a section until all the old caulk has been removed.

Step 4: Clean the area

The area has to be clean and dry so use the putty knife to scrape off any other scraps of caulk. Clean the area with rubbing alcohol and wait for it to dry.

Applying New Caulk with Caulk Gun Between the Tub and the Wall

If this is your first time and you are just learning how to caulk bathtub wide gap, it might get messy.

You can decide to use mineral spirits to clean up the area after caulking or even better, use a painter’s tape. This can be useful in providing a guide for you to follow when caulking. It also protects your bathtub and wall from the mess caused by caulking.

Before starting, you should measure the gap between the wall and the bathtub that you want to caulk. For ¼ inch, you will need one bead of caulk. You can use this standard to purchase the right amount of caulk for the wide gap.

Tools Needed:

  • Silicone-based caulk.
  • Painter’s tape.
  • Caulk gun.
  • Shaping tool.
  • Utility knife.
  • Newspapers

Step 1: Spread the Painter’s Tape

Spread the painter's tape on top of the bathtub and the wall above. The tape should be placed one-eighth inches away from the gap. Ensure that you spread the tape to stand in a straight line so it would guide you better. You should also place newspapers on the floor near you for drips of caulk.

Step 2: Load the Caulk Gun

If you are going to use a caulk gun and cartridge, open a small hole in the tip of the cartridge with a utility knife.

The hole you make should match the gap you want to fill in. Since this is for filling in a wide gap, your hole would have to be wider. Cut the tip at a 45˚ angle. You might not need the utility knife if your caulk gun has an inbuilt slicer to cut of the tip.

Step 3: Connect the Gun to the Tube

At the bottom of the caulk gun, you would see a long, spiky metal attached. This should be placed in the opening of the caulk tube. When you insert it, it would cut the seal of the cartridge and give you access to the caulk.

Step 4: Fill the Tube

Since you are using a caulk gun to seal large gaps between the tub and the wall, squeeze the trigger and feed the caulk to the gap. Do this steadily and consistently as you squeeze the gun's trigger.

Step 5: Straighten it out

After you have filled the line with caulk, pour water on your finger and run it on the line to smoothen it.

If you are using your finger, you should clean it out with a paper towel as it cannot be washed with water.  You can also use a caulk shaping tool here or the back of a teaspoon.

Step 6: Remove the Painter’s Tape

When you remove the painter’s tape, repeat the previous step.

Step 7: Clean Up

Don’t use your bathtub until the caulk has been dried up completely. You should also tidy up the work area.

What Type of Caulk Do You Need?

If you decide to seal large gaps between the tub and the wall yourself, you have to select the right type of caulk. There are different types of caulk.

When you have to caulk a bathtub, the best type of caulk are those that have a hundred percent silicone or those that are silicone-based.

Silicone-based caulk would provide a waterproof filling, last for a very long time and prevent mildew and mold. When you use this caulk, you won’t have to maintain it for a long while.

When picking a caulk in the hardware store, check the color that you want. They are usually sold in white, and come in cans or squeeze tubes.

It is best to buy quality tools that you can use to caulk other parts of your house as well as re-caulk the gap between your tub and the wall.


Now that you know how to caulk a bathtub wide gap, you can see that it’s really easy to do.

Any homeowner can follow these processes within a day and purchase the materials at a cheap price. Caulk can come in different colors, although it is advisable to get white or clear.

Caulking the large gap between the wall and the air bathtub is important in any bathroom. It would ensure that the structure of your walls and bathtub wouldn’t be affected by mold or moisture.

You also get a long-lasting caulked wall that would need less maintenance and attention. You can enjoy your time in the bathroom without being worried about mold, moisture or the open gap between the wall and tub.

With these easy steps, you can seal large gaps between the tub and the wall and maintain your home, whenever the existing caulk has become brittle and old.

Scroll to Top