Best Caulk for Exterior Windows and Doors: 6 Top Choices

When it comes to protecting your home's exterior, one of the first things you have to take care of is sealing your windows and doors with caulk. The right caulk acts as a shield, protecting them against air leaks and water damage, as well as improving their energy efficiency.

If you've never applied caulk before, you're likely wondering what the best caulk for exterior windows and doors is, right? With so many options on the market, it can be difficult to choose the right one, especially with the pressure that if it doesn't work, the insulation of your windows and doors will be compromised!

Therefore, in this guide, we'll break down the top caulks that can be used for exterior windows and doors, highlighting their unique features. By the end of this article, you will understand the basics of different types of caulk, which will help you make a decision that's right for your home.

Key Takeaways

• Among the best caulks for exterior windows and doors are silicone, polyurethane, hybrid, and butyl rubber caulks. Acrylic latex caulk and siliconized latex caulk can also be used on exterior windows, but they are not as resistant as other types of caulk.
• When choosing a type of caulk, consider its durability, ease of use, adhesion properties, flexibility, paintability, and suitability for specific materials.
• If you live in a region with a harsh climate, you should apply butyl rubber caulk around your windows and doors, as it is the most durable caulk on the market.

What Are the Best Caulks for Exterior Windows and Doors?

When selecting caulk for your exterior windows and doors, it's important to choose products that offer durability, weather resistance, and flexibility. To help you make the right choice, we've compiled a list of some of the best caulks on the market that provide reliable protection against the elements, prevent air and water leaks, and enhance your home's energy efficiency.

Here's an overview of the key differences between them, which we'll discuss in detail below:

As such, what are the best caulks for exterior windows and doors?

1. Silicone Caulk

Silicone caulk is probably the most widely used type of caulk for exterior windows and doors. It is:

• Highly adhesive.
• Suitable for different materials, including vinyl, metal, and fiberglass.
• Durable and flexible, ensuring a long-lasting seal, as it expands and contracts when temperatures change without cracking.
• Waterproof and weather-resistant, thus perfect for exterior applications.
• Able to withstand UV exposure and temperature fluctuations.

Some silicone caulks, like the Gorilla Waterproof Caulk, are also resistant to mold and mildew growth although this is usually more important for indoor applications. This type of caulk adheres and dries pretty quickly, sometimes within 30 minutes of application, but it still requires 24 hours for a full cure.

Before purchasing silicone caulk, check its label to ensure it is suitable for your door window frame material. Moreover, keep in mind that you won't be able to paint over silicone caulk because paint simply does not adhere to it, so it may not be the best to use on your home facade, for example.

2. Polyurethane Caulk

Polyurethane caulk performs well in high-stress areas, offering a robust waterproof seal for fluctuating conditions. So, it works well on windows and doors that are opened and closed frequently. Moreover, this caulk adheres better to wood. Polyurethane caulk is:

• Highly flexible, resisting cracking and loosening over time
• Moisture- and corrosion-resistant
• Suitable for both indoor and outdoor applications
• Suitable for different materials, including metal and wood
• Suitable for painting

On the downside, polyurethane caulk is not as durable as silicone caulk as it's made from organic materials. It usually lasts only five years, maybe 10 if the window or door is not always exposed to sunlight and movement. Another thing to consider is that polyurethane is not resistant to UV damage. Some products, though, may have additives that improve their performance under sunlight. Last but not least, this caulk requires a longer curing time, usually between 7 to 10 days, necessitating careful planning before application.

3. Hybrid Caulk

Hybrid caulk contains both silicone and polyurethane, thus combining the advantages of both. This caulk:

• Is resistant to moisture, chemicals, and UV rays.
• Has better bonding properties.
• Features superior flexibility, so it can expand and contract with the surfaces it's added to.
• Is paintable, and you can match it with the overall window, door, and home design.

On the other hand, hybrid caulks are more expensive and have longer curing times than silicone caulks.

4. Butyl Rubber Caulk

Butyl rubber caulk is probably the best caulk for exterior windows and doors, especially for homes in harsh climates. This is the most durable caulk on the market, renowned for its durability and performance in extreme conditions. It has excellent adhesion and water-resistance properties, offers a flexible seal that doesn't crack in extreme temperature fluctuations and can withstand UV exposure with ease.

Butyl caulk is not usually the top choice when it comes to windows and doors, being primarily used in sealing exterior gutters, pipers, and roof vents. However, you can definitely use it on windows and doors that require this extra protection against weather conditions. Plus, you can also paint over butyl rubber caulk, although it needs a few days for a full cure.

On the other hand, butyl caulk may be a bit more difficult to apply than other types of caulk.

5. Acrylic Latex Caulk

Acrylic latex caulk is popular among DIYers for its ease of application and effective sealing properties. However, it is primarily used as an interior caulk, so it's not the best caulk for exterior windows and doors unless they aren't exposed to too much water. This caulk is not as water-resistant as silicone or polyurethane caulk, but if you live in a region with a dry climate, you can try sealing your windows and doors with it.

A major advantage of acrylic latex caulk is the fact that you can paint over it, ensuring a finished look that matches your home’s aesthetic.

6. Siliconized Latex Caulk

Siliconized latex caulk is a latex caulk that contains a small amount of silicone that improves its flexibility, adhesion, and durability. The silicone also improves the caulk's water-resistance properties. It can be applied easily and can be painted over because its primary component is latex, not silicone.

Although siliconized latex caulk can be used on exterior windows and doors, it may not be the best for high-movement joints or windows and doors that are exposed to extreme temperature fluctuations. In this case, pure silicone, polyurethane, or butyl rubber caulks would be better. Conversely, siliconized latex caulk may be best for interior windows and doors.

Why Is It Important to Choose a Suitable Caulk?

Choosing the right caulk for exterior windows and doors is crucial because it effectively seals any gaps that can serve as entry points for air and water to seep into the window frame and surrounding wall. The right caulk will cover these gaps, protecting your windows from water leaks. It also ensures the window frames are not at risk of becoming rotten or moldy. Additionally, proper caulking improves the insulation of doors and windows, potentially lowering your energy bills.

A suitable caulk must be able to withstand exterior weather conditions; otherwise, it could crack and compromise the protection. This is why it's important to assess all types of caulk on the market - to avoid using one that is better for interior windows that are not exposed to water, sunlight, and fluctuating temperatures.

Lastly, if you plan to paint over the caulk for aesthetic reasons, it’s important to choose one that’s paintable.

Some Tips for Applying Caulk

Now that you've chosen the best caulk for exterior windows and doors, it's time to apply it! To help you in this process, we've prepared a list of useful tips:

• Always check the label of the caulk you plan to purchase to make sure it's suitable for the window/door you need to seal.
• Exterior caulk is not meant to fill very large gaps. If there are any gaps around your windows or doors larger than 1/4 inch wide, fill them with a foam backer rod first and then apply the caulk over it.
• Use a high-quality caulking gun that will make it easier to apply the caulk.
• Cut the tip of the caulking tube at a 45-degree angle, as it will help you apply it more easily.
• Never apply a new caulk bead over the old caulk bead. Always remove the old caulk first. This can be done with a utility or putty knife, as well as with a commercial caulk softener.
• Clean the surface thoroughly before applying the new caulk. If the surface is not clean, the caulk won't adhere properly. You can use rubbing alcohol to ensure the area is spotless.
• Seal gaps around your windows and doors with caulk during the summer. It's best to apply it when it's not raining to allow the caulk to dry and cure.
• If the window is small, apply a continuous bead on each side. This way, you ensure it's uninterrupted and smooth. If you're applying caulk on large doors, you can apply two caulk beads that meet in the middle.
• Make sure to avoid the weep holes in your windows and doors. These are tiny holes at the bottom of the frame that provide an escape route for accumulated water. Applying caulk over them will block them.
• Make sure to avoid any movable window parts, as applying caulk on them will seal them shut. Check our comprehensive guide to learn where not to caulk around windows and doors.
• Work slowly to avoid applying too much caulk.
• Smooth the caulk bead to eliminate any air pockets and enhance adhesion.
• Once applied and cured, caulk needs to be inspected regularly, especially in the beginning, to ensure it was applied correctly. Then, you can check it every few months.

Frequently Asked Questions

What is the best type of caulk for waterproofing exterior windows and doors?

Silicone caulk is the ideal choice for weatherproofing exterior windows and doors because of its superior flexibility, UV resistance, and durability. It ensures a long-lasting seal against the elements. If you live in a region with a very harsh climate, you can also apply butyl rubber caulk, as it's the most resistant and durable on the market.

How long does polyurethane caulk take to cure?

Polyurethane caulk usually requires 4 to 7 days to fully cure, so it's essential to factor this into your project timeline. Make sure to allow adequate time for the caulk to set properly.

Can acrylic latex caulk be painted over?

Yes, acrylic latex caulk can be painted, allowing you to achieve a cohesive look with your home’s exterior. Just be sure to use a type of paint that is durable enough to resist cracking and flaking over time.

Can you paint over old silicone caulk?

No, you cannot paint over silicone caulk because the paint will crack and fail. Therefore, if you need to paint over the exterior caulk, you can apply butyl caulk, which is paintable and more durable.

Can you caulk over old caulk outside windows?

You should never caulk over old caulk outside windows because the new bead won't adhere properly, and you will have to start over.

What tools are essential for effective window caulking?

For effective window caulking, essential tools include a putty knife, painter's tape, commercial caulk removal, and rubbing alcohol. These tools ensure clean surfaces and straight seal lines for a professional finish.