You’ve finished a project, and now it’s time to fill all those pesky little gaps. But when you get to the sealant aisle, there’s a hundred different caulk and silicone choices. But what’s the difference?
Caulk and silicone are both types of sealants that make joints air and watertight. While latex caulk is less expensive and easier to work with, silicone is more durable under extreme weather conditions, and can be used as a binder as well.
There are plenty of other things to consider when choosing a sealant, so keep reading!
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When To Use Caulk
“Caulk,” aka, latex acrylic caulk is your best friend when sealing dry cracks around the house.
It’s cheap, easy to work with, and easy to clean up. It dries quickly, and is paintable.
And it makes everything look better.
See the gaps in the molding of this desk:
Caulk to the rescue!
The edges of this board and batten? Caulk:
The seams on this pegboard wall? More caulk:
If there’s an unsightly gap, and I’m working in a relatively dry area of the house, I’m using caulk, because it’s so much easier to use than silicone.
But the big downside of caulk is that it doesn’t withstand harsh conditions very well. This includes water, extreme temperatures, and expansion and contraction of the space around it.
Regular water exposure will cause caulk to mold and eventually break down. Extreme temperatures will cause it to crack.
And caulk is rigid, so when the materials around caulk expand or contract, the caulk doesn’t change. This means that either a crack appears, or the caulk pushes out of the space.
My DIY butcherblock shop countertops are a great example of this. I (foolishly) filled the empty space between the wood with caulk during the winter. Now it’s summer, and the humidity has caused the wood to expand.
Do you see how the caulk is being pushed out of the cracks? It’s fine, I’ll just peel it off, but it’s a great example of why caulk isn’t the ideal substance to use between materials that will change size.
All this to say, caulk is perfect for indoor, fairly dry spaces. But bathrooms and exterior areas are going to need something stronger.
When To Use Silicone
Silicone is significantly more durable than caulk. It expands and contracts with the materials around, and holds up in extreme weather.
Silicone is also a binding material – it can hold two materials together in a way normal caulk just cant.
But silicone is messy. It doesn’t clean up with water, which makes it a pain to apply. It’s also more expensive than caulk, which is another reason to only reach for the silicone when your project really requires it.
So when does your project really require it?
Exterior Applications
If you’re applying sealant outside, where it’s going to see extreme temperature changes, as well as rain, snow, and regular weather, then silicone is the way to go.
If there isn’t a specific type of silicone for your application, then All-Purpose Silicone is your best bet.
Bathrooms
In addition to the regular water mess that appears in bathrooms, bathrooms are generally humid places. Silicone is the way to go.
Most of the time, you’ll want to purchase a specially formulated silicone mixture for the exact space you’re working on.
So if you’re applying sealant to a bathtub, you’ll probably want something described as “Tub and Tile Silicone Caulk.”
If it’s to a doorframe or window in a bathroom, you’ll want something like “Door, Window and Siding Silicone Sealant.”
Note that if you’re going to paint the silicone, you want to make sure to get a type that is specified as paintable. Not all silicones can be painted, but formulations are getting better and better, so you’ll hopefully be able to find one for your purpose that can be.
Sinks
I’m making this it’s own category, because sinks are found outside bathrooms too! And sinks are wet, as you probably realize.
So silicone is the way to go. But this isn’t just a case of sealing gaps, but also an example of binding.
Most sinks are held in place by silicone securing them in place. As an example, on this vanity makeover, I secured the sink top in place with silicone.
I used an All-Purpose silicone for the binding, since I wanted to make sure it’d be strong enough to hold the sink in place. While the tub and tile silicone is certainly waterproof, I wasn’t confident enough in its binding properties to use it.
Caulk Vs. Silicone: A Quick Comparison
As a quick recap, here are the properties of caulk compared with the properties of silicone:
| Caulk | Silicone |
| Inexpensive | More Expensive |
| Easy to clean, water-soluble | Messy |
| Easily paintable | Only specially silicone is paintable |
| Rigid, wont expand or contract | Ideal for areas that expand and contract |
| Good for sealing cracks in dry places | Good for sealing cracks in high-moisture locations |
| Not a binder | Is a binder – can work to seal two materials together |
I keep caulk in inventory, but I do a lot more woodworking and interior house projects than I do exterior work, so caulk is a lot more handy to me than silicone.
Obviously, your situation might be different!