No one wants mold on their caulk. Moldy caulk is unsightly not to mention a health hazard. What a lot of people don’t realize is that cleaning caulk doesn’t actually remove the mold. Cleaning and removing are two different things. The best approach to dealing with mold on your caulk is to simply remove and replace it.
Now, once you have removed the moldy caulk, you don’t want to just throw some new caulk in willy nilly. You need to select the caulk you are going to use carefully. Why? Because you don’t want to have to repeat all that hard work a few months down the line. Ideally you would like your caulk to stay mold free forever right?
Good news! There is mold resistant caulk! Yep – you read that right. There are actually brands of caulk with special additives to prevent mold.
So let’s get right to it and discuss all things caulk including which mold resistant caulks I think are best as well as which ones I recommend to caulk around a toilet, in a shower, around windows and more. Feel free to use the Table of Contents to jump ahead of you would like.
- What Is Caulk?
- Why Use Caulk?
- Does Mold Grow Under Caulk Or On Top Of Caulk?
- What Makes Caulk Mold and Mildew Resistant?
- Types Of Mold Resistant Caulk
- Where Do I Need To Use Mold and Mildew Resistant Caulking?
- How To Use Mold Resistant Caulk
- The Best Mold Resistant Caulk For Your Home
What Is Caulk?
Caulk is a moldable material that’s used to fill in and seal gaps throughout a structure. That’s it. Simple huh?
Why Use Caulk?
Houses are living things in a sense. They shift, breathe, and move throughout the years. This means that little gaps open up where there were none when the house was new. Caulk can seal those up easily and in a lot of cases without being noticed.
In addition to that, there are areas of your home that need additional sealing off from moisture intrusion, pests, and air. Caulking performs the essential function of keeping water and outside air where they belong.
Does Mold Grow Under Caulk Or On Top Of Caulk?
Mold grows wherever the heck it wants to. It’s a jerk like that. So mold can grow under caulk and on top of caulk.
There is a pretty easy way to tell whether or not you are dealing with mold on top of caulking.
- Soak a cotton ball in bleach (typically I do not endorse bleach to kill mold but we aren’t using it for that reason).
- If the mold “disappears” in 30 seconds this means the mold is on top of the caulking. If it is still there then the mold is under the caulking.
Having said that – there can still be mold growing under the caulking where you can’t see it coming through yet. So just become the surface mold disappears doesn’t mean that there is ONLY mold on top of the caulk. It could still be under it.
This is another reason why I advocate for removing any caulk with mold growth and replacing it with mold resistant caulk.
What Makes Caulk Mold and Mildew Resistant?
There are two reasons that caulk is considered mold proof.
- It is moisture resistant. Silicone caulk is more waterproof and flexible, so it better resists rot, rarely cracks with thermal expansion (when the shower or tub material expands or contracts with temperature changes), and lasts longer against mold penetration.
- It contains a EPA approved Biocide (also known as a mildewcide) that comes with a guarantee to keep mold from forming for a certain period of time. To learn more about why I don’t love Biocides, read my posts on Mold Removal Sprays.
Remember – mold resistant caulk won’t prevent mold forever. Be sure to look at the individual guarantees as well as recommendations for proper care.
Types Of Mold Resistant Caulk
For interior use (which is what we are discussing today), there are two main types of mold resistant caulk.
#1 Acrylic Caulk
Acrylic caulk is generally regarded as the best residential caulking option, particularly for sealing surfaces prone to repeated mold infestation. Typical areas recommended for acrylic caulking include bathroom surfaces like sinks, tubs and kitchen countertops.
Acrylic caulk is highly resistant to mold and easy to use. This is why most non-handy types of homeowners prefer to use it. You can’t mess it up too much. 😉
Acrylic caulk can adhere well to most household surfaces. It also offers a reasonably-good painting surface.
Acrylic caulk is available in two options:
1. Acrylic Latex Caulk
This is a water based formulation that is easier to handle and a lot easier to keep clean.
2. Blended Acrylic Caulk
This is slightly siliconized and known as a silicone blended acrylic caulk. This is different than silicone caulk which we will discuss below.
Blended Acrylic Caulk is very durable against moisture seepage and is highly recommended in areas wherein moisture penetration is a perennial issue.
#2 Silicone Caulk
These caulks have gained a lot of popularity in the past decade. Silicone caulks offer a slightly higher degree of mold resistance since they are fully synthetic materials.
Silicone caulk has long been the top choice among professional contractors for sealing wet and tricky surfaces like ceramic tiles, glass edges and porcelain. They have much better adhesion to off surfaces than acrylic caulk does.
Silicone caulk doesn’t crack easily. This makes it easier to scrape-off any mold spores and re-patch the silicone caulk strip.
There are two ways that silicone caulk is cured.
- Neutral Cure: This is ideal for wood and metal surfaces.
- Acid Cure: You will need to use this one for nonporous surfaces like glass or glazed tiles. Acid cure silicone can corrode metal and may also cause damage to plastic materials.
That downside to silicone-based caulk is that it is not as long-lasting as acrylic water-based caulks. It may offer better mold resistance but it presents repeated expenses in terms of more replacements. Further, silicone caulk surface isn’t very easy to clean.
Where Do I Need To Use Mold and Mildew Resistant Caulking?
This is a commonly asked question on the internet and one that makes sense. After all why not use mold resistant caulk anywhere you possibly can?
Areas you should seal with mold resistant caulking include:
- Around all sinks where they meet the countertop
- Around the bathtub / shower where it meets the surround, floor and walls. If the surround is more than on piece the corners will need to be caulked.
- Holes where the plumbing comes through the wall or floor
- Around the base of the toilet however if the toilet seal fails, this will trap the water under the toilet and cause the floor to rot. Make sure you are practicing proper mold prevention in the bathroom to ensure this does not happen.
- Around the kitchen counter where it meets the wall or backsplash
- To seal gaps between, above, and below moldings and baseboards
- To seal holes, gaps, and cracks around holes in interior framing, especially around plumbing or electrical conduits (fireproof caulk might be the better option around electrical conduits)
- Around window frames. Be careful not to seal window weep holes! Designed to let water out of your windows, these small openings should never be sealed.
- Around door frames.
How To Use Mold Resistant Caulk
Caulk application is pretty standard. While there are some mold resistant caulks that comes in a ready to use squeezable tube, they are not what I recommend. A good old fashioned 10-ounce tube of mold resistant caulk as well as a caulking gun are truly the best method to use.
How To Apply Mold Resistant Caulk For Maximum Effectiveness
- Any tube of caulk has a pointed tip. Use a utility knife to cut the tip diagonally at the very end. You want the hole to be small, so don’t cut lower down the tip where the opening gets wider.
- Poke a hole in the tube of caulk so it can come out. There’s a small piece of wire on the caulk gun that swivels out from below the shaft. Take this piece of wire and insert it through the tip of the caulk until you feel it puncture the tube. Do this a few times. Wipe off the wire when you pull it out.
- Put the tube of caulk into the shaft of the gun and pull the trigger until you feel it meet some resistance.
- You want to make sure that the tip of the caulk is clean before applying it so give that a quick check and wipe of any dirt or debris that may have stuck on.
- Place the tip of the tube on the crack you want to fill and gently pull the trigger of the gun as you pull the tube across the crack. You want a small, thin, uniform line of caulk over the surface of the crack. You should be continuously moving the caulk gun, not staying in one spot. If you linger in one area too long the caulk will come out in a blob and you aren’t going to want to deal with that.
- Lightly smooth the caulk into the crack. I wear gloves and just use my finger. You want to move your finger in one direction. When you get to the end of the areas you are sealing, wipe off the extra caulk and then clean off your finger.
- Move on to the next area and repeat the process.
A Quick Caulking Tip
Make sure your caulk doesn’t harden too quickly. This allows for breakage which can allow for moisture penetration. It is best to use your caulk in cooler temperatures or to place a fan in the room where you caulked to circulate air.
Also, allow the caulk to dry for 24 hours at least. I give it 48 hours but that’s just me. Even if a caulk says it is ready for use after a short drying time, don’t risk it. Give it time to fully cure.
The Best Mold Resistant Caulk For Your Home
Below are the top brands of mold resistant caulk. Some are meant for use in specific areas of your home while others are more general use. Whichever you choose you can rest easy knowing you have added another layer of mold protection in your home.
#3 GE Silicone 2 + Kitchen & Bath Caulk
GE Silicone 2 + Kitchen & Bath Caulk is 100% silicone and 100% waterproof with 10-year mold-free product protection. It is a neutral cured caulk, which you can use with the confidence that it gives you 10-year mold-free protection.
GE Silicone 2 + is technically ready for water exposure in as little as 30 minutes although like I mentioned previously I would wait 24 hours.
It is formulated for sealing sinks, tubs, showers, fixtures, countertops, backsplashes and plumbing projects.
Pros of GE Silicone 2 + Kitchen & Bath Caulk
- Highly resistant to the growth of mold
- Excellent adhesion
- Smooth application
- Permanently flexible
- Will be ready for exposure in 30 minutes
- Will not discolor most metal and stone
- Resists shrinking and cracking
- Lifetime durability guarantee
- Fits well with most caulking guns
- Excellent heat resistance
- 100% American
- Low odor and low VOC (meets CARB VOC limits)
Cons of GE Silicone 2+ Kitchen & Bath Caulk
- Not entirely clear on setting
- Tubes sometimes burst
- The product has an expiration date
#2 DAP ALEX PLUS Acrylic Latex Caulk Plus Silicone
DAP ALEX PLUS Acrylic Latex Caulk Plus Silicone is a professional quality caulking product formulated to last. It is an all-purpose adhesive caulk ideal for a wide variety of applications for interior and exterior use.
ALEX PLUS contains silicone, which allows for excellent adhesion and flexibility to resist expansion and contraction without cracking. This makes it more durable.
This caulk is best if you want to paint over the caulk. It’s also safe for surfaces that will come in contact with food, which makes it great to use on kitchen counters.
The manufacturer offers a 35-year guarantee.
Pros of DAP ALEX PLUS Acrylic Latex Caulk Plus Silicone
- All purpose formula
- Premium quality and superior performance
- Exceptional strength and adhesion
- Highly flexible and durable for a waterproof seal
- Comes in more than one color
- It can be painted on
- Cured caulk is mold and mildew resistant
- Easy to apply
- Easy water clean-up
- Exceeds ASTM Specification C834.
- Great for both interior and exterior use
Cons of DAP ALEX PLUS Acrylic Latex Caulk Plus Silicone
- Messier than other caulks
# 1 Sashco Lexel Adhesive Caulk
Sashco Lexel Adhesive Caulk is the “duct tape” of all caulks. Super-elastic. Superior adhesion. Paintable. It seals around anything: tubs and shower stalls, sinks and counter tops, window frames and door frames, PVC and metal pipes. Apply to wet or dry surfaces, indoors and outdoors. It’s tough and can handle up to 400% joint movement. It’s scrubbable. It sticks to just about anything. Sashco Lexel CLEAR Adhesive Caulk is 19 times clearer than silicone and won’t yellow or cloud up over time.
This is a mold resistant caulk that won’t let you down.
Pros of Sashco Lexel Adhesive Caulk
- Survives routine scrubbing with household cleaners, including abrasive cleaners.
- Extremely elastic. When the surface moves, Lexel moves.
- No cracking, tearing, or pulling away for a lasting, permanent seal
- Instantly waterproof
- Cured sealant is mold and mildew resistant
- Ultra clear sealant. It won’t yellow and won’t go cloudy.
- Won’t freeze
- Adheres to almost all building materials
- Can be used on wet surfaces
Cons of Sashco Lexel Adhesive Caulk
- Stronger odor
- Lower VOC but not as low as the others mentioned
- Sometimes does not adhere to as expected
- No warranty or guarantee
Be sure to check out my post on Mold Resistant Building Materials! It has all your needs covered.
If you would like to add a layer of mold resistance to a shower, bathroom, and window frames and sills, give everything a good spray down with Endurance Bio Barrier! Let me tell you…this stuff really works to prevent mold. Depending on where you use it Endurance Bio Barrier can prevent mold from growing for anywhere from 6 months to 25 years. Yes, 25 years. That’s beyond awesome.