When mold is growing on shower caulk, and not behind it, removal is fairly easy. In this post, a professional cleaner shows you how to do it.
Time Less than 1 hour
ComplexityBeginner
CostLess than $20
Introduction
When mold is growing on shower caulk, and not behind it, removal is fairly easy. In this post, a professional cleaner shows you how to do it.
Mold loves moisture, and no place in the house has more of it than the inside of the shower. Given the chance, mold will grow in tile grout, on tiles, around the drain and on the caulking. Mold growth is difficult to prevent in such a water-rich environment, and if you don’t know how to clean mold from shower caulking, your bathroom will never look one hundred percent clean.
Mold growing on the caulking isn’t the same thing as mold growing behind it. When mold is growing behind old caulk, you really have to remove the caulk to do a thorough cleanup, and I can tell you from years of home maintenance experience that this can be a tough job. Although there are products that soften silicone and weaken its bond to the surface to which it’s stuck, nothing actually dissolves it, so the job necessarily involves scraping and pulling.
Cleaning mold is easier when it’s growing on the caulk’s surface, however. In this post, professional cleaner Michael Bogoyavlenskiy shows you how to clean mold from shower caulking.
What Causes Mold in Shower Caulking?
Mold spores are everywhere, but they only grow into mold colonies in places where they find moisture, nutrients and warmth. There is plenty of moisture and warmth in a shower stall, and soap and shampoo deposits, along with stray strands of hair and other debris, provide the organic matter for nutrition. Some mold species can even feed on the caulk itself.
- Pro tip: To prevent mold from growing in the shower stall, provide plenty of ventilation. After showering, leave the shower door or curtain open, open a window, leave the bathroom door open and run the bathroom exhaust fan long enough for everything to dry out.
Tools Required
- Bowl
- Toothbrush
Materials Required
- Baking soda
- Household bleach
- Paper towels
Project step-by-step (5)
Step 1
Gather your supplies
For this procedure, you’ll need two ingredients: household bleach and bicarbonate of soda (baking soda). You’ll also need a bowl, a toothbrush and some paper towels.
“You need to use actual, standard bleach for this,” says Bogoyavlenskiy. “Make sure it isn’t ‘toilet cleaner’ or any other product, as these have a lower concentration of the ingredient you need, which is sodium hypochlorite.”
For those sensitive to bleach, Bogoyavlenskiy recommends hydrogen peroxide as an alternative.
Step 2
Make a mold-killing paste
Mix standard household bleach with bicarbonate of soda (baking soda) in a bowl until it’s the consistency of toothpaste.
- Pro tip: Bogoyavlenskiy recommends this method because it has less effect on the appearance of the caulk than commercial mold-cleaning products. “A lot of over-the-counter anti-mold products don’t work on caulk,” he says. “They will kill the mold, but the bigger problem is the staining it leaves behind, which can make the issue appear worse than it is.”
Step 3
Spread the paste
Use a toothbrush to spread the paste liberally on the moldy caulk. “Although it’s optional,” says Bogoyavlenskiy. “I recommend covering the paste with a paper towel or something similar, just to prevent it from drying out.”
Leave the paste undisturbed for one to several hours or overnight.
Step 4
Wipe and scrub
Remove the paper towels and use them to wipe the paste off the caulk. This should remove the mold and any discoloration it has caused. If some areas are still discolored, scrub them with the toothbrush. “If any of the mold isn’t lifting, repeat the process until it’s as clean as you want it to be,” says Bogoyavlenskiy.
Step 5
FAQs
When should you replace shower caulking?
Now that you know how to clean mold from shower caulking, you should do it periodically to keep the caulk looking its best. However, a paste won’t help if you have to clean mold growing behind the caulk and creeping up the wall or onto the shower pan. The paste can’t get behind existing caulk.
When it’s clear that mold is growing behind caulking in the shower, it’s time to remove and replace the caulk. Bathroom caulk is silicone-based, and you can soften it with mineral spirits, alcohol or vinegar. Once it’s soft, use a utility knife, metal paint scraper and your fingers to cut, scrape and pull off the old caulk. After all the old caulk is gone, you can use the paste to clean the mold that has been growing behind it. Rinse the area with water and let it dry out before you re-caulk.
How often do you need to re-caulk a shower?
Most sources agree with British manufacturer United Silicones that silicone caulk lasts at least 20 years outdoors and in the shower. If you keep your shower well-ventilated and dry, silicone shower caulk can easily last longer than 20 years, but if moisture conditions promote mold growth, the caulk could start peeling and need replacing sooner than that.
About the Expert
- Michael Bogoyavlenskiy is the CEO of Cleaning Express, a domestic cleaning company and a professional facilities’ management provider servicing luxury offices, business centers, retail companies, schools, entertainment venues, as well as private and government-run health clinics.
Source
- United Silicones: How Long Should Silicone Sealant Last Around Your Home?; (2025)
