What Type of Caulk to Use? Sealant Types and Their Uses.

Caulk is a handy product for sealing cracks and filling divots. It can be squeezed out into the opening, then flattened to fill in the space.

However, not all types of caulk are the same. While the silicone-based ones are the most popular, they are expensive, and there are better options for interior use.

Different Types of Caulk products
To know which is right for your job, you’ll have to know the different types of caulks available.

Different Types of Caulk

Although most caulk types are applied roughly the same manner, the different types reflect the different substances from which they are made. What follows are five basic types of substances available for caulk. Each one has its advantages and issues.

1. Acrylic Latex Caulk

One of the easiest caulks to apply, acrylic-latex caulk has the advantage of being easy to clean up using water. This type of caulk adheres to most surfaces, including tiles, wood, drywall, etc., and offers moderate resistance to water.

However, it has one major disadvantage. The acrylic-latex caulk is not UV resistant, and hence it is not suitable for exterior use.

While the acrylic-latex caulk is fine for most general-purpose interior jobs, for external use, you should consider products that include silicone for extra flexibility and adhesion.

2. Silicone Caulk

Silicone is a nonorganic material that is perfect for exterior use since it is resistant to UV or ultraviolet light. Pure silicone is technically a sealant that is quite durable and offers excellent water resistance.

However, 100% silicone is difficult to paint over as it lacks proper adhesion once cured. If you plan on using caulk for interiors or to paint over, then acrylic is a better choice.

3. Hybrid Caulk

This is a combination of silicone and acrylic caulk, with the addition of silicone offering better moisture resistance. It’s also easier to apply compared to 100% silicone or polyurethane, although not quite as easy compared to acrylic.

Man holding Acrylic plus Silicone hybrid caulk
The one downside is the cost which can be expensive considering its advantages and demand.

4. Polyurethane Caulk

Polyurethane is a highly versatile, strong, and flexible substance. Because of its water-resistant nature, it’s perfect for driveways and other areas exposed to the elements. However, it’s not easy to work with, so you should check the label to ensure that it is right for the job.

It also takes considerable time to cure, and you may have to wait several days before you can paint on it.

5. Butyl Rubber Based Caulk

This is a specialty type of caulk that is used only for exterior surfaces. Because it is water-tight and can withstand wide temperature ranges, it is perfect for metals such as aluminum, rubber, stone, plastic, and exterior wood and vinyl. You can also use it to seal siding, gutters, and concrete.

However, you should wear protection for the eyes and hands as it can cause irritation. Plus, cleanup is problematic if you get it on your clothing or shoes.

Flex shot is a popular rubber-based sealant.

What Type of Caulk Should You Use?

The type of caulk you should be the one best suited for the job. This means knowing where the caulk will be placed, such as indoors, outdoors, or on surfaces that will be painted or exposed to moisture. Once you identify the area, then the type of caulk will be easy to choose.

What follows are several common areas where caulk is commonly used.

Caulk for Bathroom

Pure silicone sealant works best for bathrooms since it offers superior water resistance and flexibility. Your bathtub will move slightly when you fill the water and step into the tub. The flexible silicone sealant allows these movements.

Tip: Fill water in the tub before you do the caulking.

You could also use hybrid caulk in places where you want to paint over the caulk.

Bathroom Sink and Kitchen Sink

While the acrylic caulk is easy to use, it will not have the staying power needed. Instead, use a hybrid caulk or 100% silicone sealant, depending on its location.

Be sure to check the product label first before purchasing a caulk to ensure it is right for the area in which it will be applied. You can choose from different types of caulks that are waterproof and resistant to mold.

What Kind of Caulk to Use for Crown Molding?

For interior crown molding, acrylic caulk works quite well. Especially if the molding will be painted over at some point.
Acrylic caulk is easy to use and can last for a considerable time in dry environments.

If the crown molding might be exposed occasionally to moisture, then you might consider a hybrid caulk instead.

What Type of Caulk to Baseboards?

Acrylic caulk works well for baseboards. It is easy to use and can be painted over if needed.

You should acrylic-latex caulk for all your interior wood trims since pure silicone sealant will not adhere to wood properly.

For the most part, baseboards are not exposed to moisture or UV rays which is the biggest enemy of acrylic caulk. You can use hybrid caulk exterior baseboards that might be occasionally exposed to moisture and direct sunlight.

Windows (Interior and Exterior)

Of the different types of caulks available, silicone and hybrid caulk are generally the best. This is especially true for areas exposed to the elements. It is true that most silicone products cannot be painted over. However, you can use a hybrid caulk instead, which has enough adhesion to allow the paint to stick.

For the most part, you can apply the caulk to exterior windows with no problem. For interior windows that are already sealed from the outside, you can use acrylic caulk instead and paint over it. This will add to the insulation properties of the area.

Expanding Foam for Interior Use

For interiors, you may consider an expanding foam caulk. This is a specialty caulk normally made of latex that is only used for insulation purposes. Expandable foam has the benefit of being the easiest to apply. Simply place the nozzle on the area that is needed to be covered and press the button.

Exterior Siding

You will need the type of caulk that is the most water-resistant. Plus, caulk type that can withstand UV rays or ultraviolet light. If the surface is to be painted, I recommended that you choose either a hybrid or polyurethane. You get greater adhesion along with better flexibility when using either type of caulk.

If the siding is textured, then you should consider a textured polyurethane caulk. This will help match the texturing of the siding, stucco, or a rough-sawn wood appearance.

Remember that there are other applications for caulk as well, such as insulation for openings that are exposed to the outdoors. Places where pipes or conduit come indoors, may be sealed using a silicone or polyurethane caulk on the exterior.

Caulk for Insulation

Caulk also comes in backer rods and caulk strips that are also used for insulation purposes. The backer rods are larger and meant to cover areas too big for normal caulk to be used.

Just remember to have a caulking spatula to remove the old caulk first or smooth out the caulk you apply for the best results.