Caulk Vs. Expanding Foam Vs. Silicone: A Homeowner’s Guide

When you need a sealant, there are three products to know about: caulk, expanding foam, and silicone. There's not much that tells us the difference between the three. So, it raises the question—what are they, and what do they do? If you need help telling the difference, we're here to help!

You can use caulk, expanding foam, and silicone to seal cracks, gaps, and joints. One isn't necessarily better than the other; they have different purposes. For example, silicone and expanding foam are better at handling environmental conditions than standard caulk. 

A few sentences aren't enough to explain how each one is different than the other. There are a few factors to consider before choosing one of these sealants. If you choose the wrong one, it might not last long. To learn more on this topic, keep reading. 

Differences between 3 images Caulk, Expanding Foam and Silicone, Caulk Vs. Expanding Foam Vs. Silicone: A Homeowner's Guide

The Differences Between Caulk, Expanding Foam, And Silicone

Before we get to the differences, let's establish a basic understanding of what each product does. As mentioned, you can use caulk, expanding foam, and silicone to seal gaps, cracks, and joints. 

Professionals typically use them for fireproofing, waterproofing, and insulation purposes. Does that mean you use them interchangeably? Not exactly.

They have their advantages and disadvantages. If you use the wrong sealant for a job, it might crack. As a result, you'll reapply the sealant without knowing why it's failing.

Of course, you can prevent this by researching the products before you purchase them. So, let's start with the product with the most variety—caulk. 


Roofer Applying Caulk to House Chimney Flashing

Caulk is a general term that describes a range of products. As Home Depot describes it: "Caulk describes any waterproof material that fills and seals joints between building materials."

If you look at stores online or in person, you'll notice not all caulks are created equal. Some use latex, and others use rubber or any combination of polymers. In addition, some are cheap, while others can be pricey. 

There's a good reason for this much variety. 

Differences Between Caulk Materials

Caulk has different chemistries for different conditions and applications. Before you choose one, you have to consider the area you're applying it in. A few factors that come to mind are moisture content, temperature fluctuations, and surface material. 

Moisture Content

First, we need to know how often the area will get wet. If you need a watertight seal, the sealant needs to be waterproof. 

Temperature Fluctuations

Secondly, consider how frequently the temperature will fluctuate from hot and cold. Temperature fluctuations can cause materials to contract and expand. 

Therefore, the caulk you choose should be elastic to handle these conditions. Otherwise, it's going to fail at some point. 

Surface Materials

Finally, some polymers can form bonds on materials better than others. If you choose the wrong caulk, it might not adhere well to the surface. So, you have to question whether the caulk you pick is acceptable for wood, glass, plastic, or metal. 

Types Of Caulks

The few caulk you can choose from are polyurethanes, solvent-based, or water-based. 


Click here to see this polyurethane caulk on Amazon.

Polyurethane caulk is typically for outdoor usage. It's durable and flexible enough to handle outside conditions. In addition, it's a material you can paint over. 

This way, the caulk doesn't stick out like a sore thumb. You can use polyurethane caulks in areas like driveways and trim. 

Solvent-Based (Butyl-Rubber Caulk)

Click here to see this butyl-rubber caulk on Amazon.

Solvent-based caulks typically perform similarly to polyurethane caulk; it's durable and flexible. Yet again, it's another type of caulk for outdoor usage. 

However, solvent-based caulks are different because they come in various colors. Plus, you can apply them on wet substrates. Professionals will typically use solvent-based caulk for roofing jobs and gutters. 

Water-Based (Latex Acrylic Caulk)

Click here to see this acrylic latex caulk on Amazon.

Water-based caulk is the one you would use for indoor applications. They're elastic but not as flexible as solvent-based or polyurethane caulks. 

Nevertheless, they're still a good waterproof caulk. Plus, they're paintable; this is why they usually carry the name of painter's caulk.

Professionals use water-based caulk indoors because they're low in volatile chemicals, stinks less, and is easy to clean up. 

Silicone Sealant

Click here to see this silicone sealant on Amazon.

Silicone sealant is an adhesive that looks, feels, and acts like a gel. As the name implies, it uses silicone instead of latex acrylic mixtures. Silicone is used because of its elasticity and water resistance. 

Mans hand caulk skirting board with caulking gun and silicone cartrige

Silicone sealants and caulk are nearly the same. However, silicone has a few advantages and disadvantages over caulk. In terms of elasticity, silicone sealant performs the best. 

Since it's more elastic, it can withstand high and low temperatures better than caulk. For this reason, it's one product worth choosing over caulk for kitchen and bathroom applications. 

However, silicone has one downside; you can't paint over it. If you attempt to paint over it, there will be streaks.

Here's a video demonstrating the differences between silicone and caulk:

Expanding Foam

Spraying polyurethane foam from a gun to install and fix the interior door

Expanding foam is not the same as caulk or silicone. More specifically, it's more use-specific. If you see expanding foam in stores, you'll notice it comes in a can; some cans will have a long spray nozzle. 

Like caulk, not all expanding foams are created equal. Some are low-expansion, while others might expand more than you'd like. Expanding foam fills in a need that caulk or silicone can't satisfy. 

You can use it to fill in gaps and cracks where using a silicone sealant or caulk is nearly impossible. For example, use it to seal air leaks in tight spaces in an attic. 

Another area expanding foam would do well in is rough openings in doors or windows. Expanding foam will fill these areas and give you many benefits. 

It serves as a form of insulation. In other words, it's preventing air leaks. In addition, it leaves no room for pests to come through. 

Areas Where Expanding Foam Doesn't Make Sense

The main attraction of expanding foam is its ability to fill in gaps entirely. It could give you a sense that it could work anywhere. However, that's far from the truth. 

There are some areas where expanding foam wouldn't make sense. For example, you'll never want to use it to fill in cracks in house foundations. It's a bad idea. 

It begs the question—why is it a bad idea? There are many reasons why cracks can form in a foundation. Regardless, the more important part of the crack is its severity. 

Does it look like a structural problem? If it is, look elsewhere. Never use expanding foam as a fix to a structural problem. It's not a structurally-rated product. 

If you'd like tips on how to use expanding foam, here's a video explaining it in detail:

When And Where To Use These Sealants

There's a lot of information to take in. As we can see, there's a clear difference in performance between caulks. However, silicone sealants are where it can get confusing.

They perform nearly the same as some of the best caulks, but you can't paint over them. It can get a bit confusing choosing one or the other since that's not a big disadvantage. 

Fortunately, we don't have to complicate things; we can keep things simple. If you need an indoor sealant, use an acrylic latex caulk. 

However, if the area gets wet frequently, use a silicone sealant. For outdoors, you can pick between polyurethane or butyl-rubber caulk. 

Finally, expanding foams work well in areas that silicone or caulk can't reach. If you decide to use an expanding foam, follow the manufacturer's instructions for the best experience. 

Should I Use Silicone Or Caulk For Shower?

Caulk Gun Applying Silicone to shower area

Now that we've covered the information you need to know, we can get into the specifics. Let's say you need a sealant for the shower. We can limit our choices to caulk and silicone with the information we know. 

So, which one will work best for this area? Bathrooms can get wet frequently, and they face temperature fluctuations too. For this reason, silicone sealant is the best choice for sealing gaps in a shower. 

What Is The Best Caulk For Large Gaps?

Now let's take a look at a different situation. What if we need to fill in large gaps? You could try using caulk, but you'd need a lot of it to fill it in. Caulk is best for filling narrow gaps around doors, windows, baseboards, and crown moldings. 

So, there's no best caulk for large gaps. Instead, consider using expanding foam. You can fill gaps around pipes, electrical outlets, and window jambs with it.

Is It OK To Caulk Over Old Caulk?

Caulk fills in small gaps to prevent air leaks—we know that much. Over time, it will begin to wear out. At this point, we'll know it's time to reapply it. 

However, if you've never reapplied caulk, there's one detail you might miss. Should you remove the old caulk or caulk over it? Some will say it's acceptable to caulk over old caulk, but that comes with some risks

If the old caulk is shrinking, it will continue to shrink. When you apply new caulk over it, the old caulk might break the seal of the new caulk. For this reason, it will separate much earlier than you'd like. 

In general, it's better to remove the old caulk before recaulking the area. 

In Closing

Differences between 3 images Caulk, Expanding Foam and Silicone

Caulk, expanding foam, and silicone all serve a similar purpose. However, they provide certain advantages over the other. Hopefully, you can pick the one you need with confidence now. Good luck choosing a sealant! 

Before you go, do you have more concerns about expanding foam? We have other topics you can check out!

Can I Use Expanding Foam Around Heating Pipes?

Expanding Foam Stickability – Does It Stick To Metal, Plastic, Wood, Glass, & PVC?

Hydraulic Cement Vs. Expanding Foam: Which Should You Choose?

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