Introduction: Fixing Moldy Caulking in the Bathroom

About: Hey, I'm Zac, I'm a Toronto area contractor turned furniture maker and lover of DIY.

Close your eyes, try to visualize what the corners in your shower and around your tub look like. Are they pristine and spotless? If so, then then this post probably isn't for you. However, if they're anything like mine you might want to keep reading. As a contractor, I see 2 very common problems in a lot of bathrooms (including my own!) and in this post, I'm going to show you have to fix both.

The first is sloppily applied caulking. Amateur builders love to lay on heaps of silicone caulking in the bathroom. It covers a lot of sins and at first, it doesn't look THAT bad. The problem is that over time those big thick silicon lines are the perfect place for mold to grow. Ya, those black spots accumulating in the corner, those are mold, unfortunately. The more caulking you use, the faster the mold will grow and spread.

The second is that many people use white caulking in bathrooms. I get what they are thinking, there's lots of white stuff in the bathroom. The toilet, the tub, the sink, etc, it's all white. Here's the thing though, there are a million different shades of white. So there's a 99% that the white caulking isn't going to match anything in the bathroom. It's almost certainly at least a little bit off.

Let's fix both of them at the same time!

Step 1: The Video

I know many people prefer to read Instructable posts, but if you're more into video content then I've got you covered. Here's a link to this project in video form!

If you're in the majority of the people who prefer to read, then by all means, keep on scrolling. Let's start this fix this caulking!

Step 2: Supplies

It's a short list of supplies for this project. You'll need:

A tube of clear kitchen and bath silicone caulking (try to avoid the cheap stuff!)

A caulking gun

A roll of painters tape

A flat blade knife like a boxcutter or a razor blade

Step 3: Prep

The first step is going to be an easy one. Just remove everything you can so that you have room to work.

All of those shampoo bottles in the corner? Ya. They are going to have to go. Shower curtain? If you can, pull it down. The more room to work you the easier this job is going to be.

Next, give the whole shower a quick wipe down. You're trying to remove any loose dirt or water left over from the last time you used it.

It's probably a good idea to wait until after it been a while since your last shower or bath before attempting this project. The dryer, the better.

Step 4: Remove the Old Caulking

Here's where things get fun. You're going to have to cut out all of the old caulking. As far as I know, there's not easy, sure-fire way, to remove silicone caulking. It's just a matter of patience and dedication.

You'll need a thin blade, preferably a razor or a box cutter. I use a razor blade in a little holder because it makes it easy to hold and helps keep my fingers away from the blade. Please be safe when you're using any blade.

Then you're going to try to slide the blade between the deck of the tub and the caulking and slice all the way around the perimeter of the tub. You'll then do the same thing except you'll be sliding the blade between the tile or wall of the shower and the caulking.

Likely you won't get it all at first, there will be some residue, try to be as diligent as you can, and remove it all.

Sometimes you'll get lucky and once you get a good chunk of caulking pulled off you can use it to pull the rest off. This doesn't always happen though, mine just kept snapping on me :(


Once you've removed it all, give the whole area another good clean and vacuum.

Step 5: Apply Painters Tape

This step basically ensures that you're going to get a perfect application of silicone. It's also the step that most people skip or just don't know about.

You're going to take some painters tape and apply it around the perimeter of your tub and shower, masking off the area where you don't want the silicone to go. On the deck of the tub, you're going to apply it and leave it back of the wall by about 1/16 to 1/8 of an inch.

On the wall, you're going to apply it 1/16 to 1/8 of an inch above the deck of the tub. If done correctly you should have a thin, straight, unmasked line in the corner of the perimeter around your shower/tub.

While not strictly necessary I took the time to redo my entire tub surround as well. This meant doing the sides of the tub and where the tub meets the floor. I wanted to get rid of ALL of that nasty white caulking.

If you're going to be a perfectionist like me and do a lot of lines, consider breaking the process up into a couple of phases because this is a relatively time-sensitive job. Sometimes I'll do all of the vertical surfaces in 1 pass, and then all of the horizontal surfaces in another pass.

Step 6: Prep Your Silicone Tube

You're almost ready to start caulking, but let me give you a few tips first.

First, use clear silicone. It's much nicer than white silicone, and, if you apply it in a thin clean line it takes on the color of whatever surface you apply it to, which ensures an exact colour match. If done correctly it's basically invisible.

Second, make sure you buy a proper kitchen and bath silicone. They have anti-fungal agents that keep mold from growing on them. In my experience, it's usually worth it to pay the extra few dollars and get a high-quality silicone too.

Finally, third, try to cut the tip on the silicone tube to the same width as the line you're trying to apply it too. It will make the application a lot smoother and you'll waste less silicone.

Step 7: Apply the Silicone

Ok, time to load up that silicone into your caulking gun and start applying. Pick one corner, pull the trigger until caulking starts to come out of the end of the tube, and slowly work your way around the tub.

A light touch is best here, no need to lay down a ton of silicone, that's what you're trying to avoid here remember!

Don't beat your self up if you color outside of the lines a little bit, that's the whole reason you laid down the painters tape.

Step 8: Initial Wiping

After you've finished applying the silicone you're going to take your finger and simultaneously press the silicone into the corner and squeegee off any excess the whole way around.

Try to make sure you're applying a consistent amount of pressure and have a rag handy so that you can wipe off any excess silicone on your finger.

You'll probably wipe off about 3/4 of the silicone you just laid down, don't worry, that's perfectly normal. I like to do AT LEAST 2 full passes the whole way around the tub before I move onto the next step.

Step 9: Remove the Tape

Once you're satisfied you've removed most of the excess silicone it's time to peel back the tape.

Pick a corner and start peeling!

Be careful that as you peel the tape you don't accidentally rub it against anything because it's probably got a good amount of silicone still on it.

Step 10: Second Wiping

It's time for one last pass with your finger.

After the tape is removed your silicone line will have a hard edge on both the deck of the tub and the wall. In order to smooth out that edge and really blend the silicone out, you're going to do one last pass the whole way around with your finger. You don't need to press as hard as your first couple of passes, just enough to feather out the edge.

Step 11: Stand Back and Admire Your Work

Here's what my caulking lines looked like after I was done. They're basically invisible.

Not only are they much nicer and cleaner looking, BUT, because they're so much smaller there's WAY less surface area for mold to grow and accumulate. It should mean that these caulking lines stay mold-free for a long time

Step 12: Caulk the Corners (optional)

Let me preface this step by saying this: If your shower enclosure is properly waterproofed and your tiles are properly grouted, you DONT NEED TO CAULK THE CORNERS. Sorry for the caps lock, but I see this far too often and it's a bit of a pet peeve of my mine.

That being said, the grout in the corner of my shower was in pretty bad shape, so I had to re-caulk the corners. I would've much preferred not to, but in the interest of keeping the whole thing waterproof, I did.

I used the exact same procedure as before after the first application of silicone had dried.

I hope you enjoyed this post, let me know if you have any questions or comments and good luck re-caulking your showers!