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What Is the Best Caulk for Exterior Windows and Doors? 

 November 8, 2020

By  Dale Keese

Caulking exterior windows and doors is a simple task that offers significant benefits. It saves you money from energy bills, keeps water and bugs out, prevents mildew, and protects your investment. But with all the different kinds of caulk out there, how does one choose the right one?

The best caulk for exterior windows and doors is one that’s made from silicone, polyurethane, or latex. They are flexible, waterproof, impervious to fluctuating temperatures, protect from rot, last a long time, and can protect efficiently from the elements.

Caulking your home’s exterior is simple and can be a quick DIY project, as long as you are working with the correct sealer. Read on to learn about how to choose the right sealer for the job.

There are many kinds of caulk available out there, and each of them are designed for use in a specific situation in your home. Certain formulations are better adapted for exterior use:

Silicone

Made from silicone elastomers, silicone is one of the most popular choices for exterior caulk. It turns rubbery upon curing, making it extremely flexible and can expand or contract depending on the temperature. Silicone caulk is already waterproof, preventing leaks from entering through windows and doors. However, most silicone caulks can’t be painted over and don’t have the best adhesion compared to other caulks. If you require painting over silicone caulk, look for paintable formulas.

Silicone isn’t water based, and this makes it effective in preventing mold and mildew which is why it’s a good choice for sealing the exterior of your home. It might not be easy to apply but if you do it right, silicone caulk can last up to 50 years.

Polyurethane

Polyurethane has excellent adhesion to a wide range of materials and can even stick two different types such as wood and plastic. It’s a terrific all-purpose choice for exterior caulking. They can be used on many kinds of materials because they are non-corrosive. The issue with polyurethane caulk is that they aren’t UV resistant which is why they need to be painted over in order to protect from damage caused by UV rays. It can last you anywhere from 5 to 10 years, depending on sunlight exposure as well as how often the joints are moved.

Latex

Water-based latex caulk is ideal if you intend to paint over it in order to match the rest of your façade. Latex is extremely durable, and can last 10-20 years on average. It’s a great choice if you need to fill in the side of wood, or small gaps that are found in door and window frames. The drawback of using latex caulk is that it doesn’t work well in cold climates; it won’t adhere well if the temperatures drop to below 40 degrees. On the other hand, it works well in dry weather conditions.

Take note that when shopping for caulk, always look for products that indicate they are meant for exterior use.

Other Factors to Consider When Choosing Your Caulk

Elasticity or elongation

When looking for exterior caulk, you should ask about how much it can stretch before it starts to peel or crack. The more the caulk can stretch, the better protection you can expect for your windows and doors. This is measured by its elongation. Look for sealers that can stretch at least 20% for the best results especially if you live in climates where temperatures rise and drop in the extremes during the summer and winter. Alternatively, you can also look for sealers that are designed to stretch.

Application

Caulks are available in cartridge, squeezable tube, ropes, and aerosol cans; each of these are meant for a variety of situations around your home. For easy application on windows and doors, look for caulk in a squeeze tube with a fine pointed tip so that you can squeeze out just the right amount that you need. If you are working on a small project, opt for a small squeeze tube that’s around 3 to 6 ounces. You may also see caulk strips, though these are intended for use in bathrooms, so they are not ideal for exterior windows and doors.

Appearance

For exterior millwork such as windows and doors, they should blend in with its design and be invisible to the naked eye, as much as possible. Look for caulks that match the color of your millwork; the good news is that caulk comes in a wide variety of colors

Application Advice

Caulking can easily be done without outsourcing the help of a professional. Having said that, it requires patience and steady hands, so this isn’t a DIY job that you should be doing if you are in a hurry.

Before you get started, thoroughly clean the areas that you want to caulk. All old paint or caulk should be removed using a putty knife; this way, you’ll be working on a clean, flat surface which gives the new caulk better chances of adhesion. Be sure to dry the area completely so that you aren’t locking in moisture.

Most caulks will completely dry in at least 24 hours, depending on the manufacturer’s directions. If, after application, you find that the caulking has shrunk, feel free to apply more to make sure that it’s a solid seal.

Basic Application Instructions

Proper application of caulk should never be underestimated. This is where the success of your project lies. Here are the steps you need to undertake:

  1. 1
    Inspect the caulk. Make sure you have all the tools you need. If there is existing caulk, look for areas that need replacement; you can tell by looking for splits or cracks. If some part of the caulk has stayed in good shape, leave it alone.
  2. 2
    Get rid of old caulk. For the damaged caulk, use a putty or utility knife to carefully scrape it off. A wire brush is recommended for removing tiny remnants. Finish it off by using a rag to clean the area. Ensure that the surface is completely dry before applying the new caulk.
  3. 3
    Apply the caulk. Load the squeeze tube into your caulk gun, then cut the tip using an angle. Start with small amounts, and add more only if you feel that it’s needed. When it comes to caulk, less is always more. Allow at least 24 hours to dry.

It’s always best that you should follow the manufacturer’s directions; these steps may change depending on the type of caulk used.

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Frequently Asked Questions

How often should exterior windows be caulked?

If your home is newly built, replace the caulk after one year. Following this, or once you are already living in a home built a few years ago, caulking should be replaced every 5 years. The frequency at which you replace the caulk in windows and doors would depend on the quality of the caulking job, so it’s always best to check for cracks and peels routinely. If you notice a sudden spike in your electricity bill, you may want to check the caulking to see if it’s time for a replacement.

Will caulk cure if it gets wet?

If caulk gets wet before it properly cures, it may not adhere properly which can lead to gaps and leaks. It will also take much longer for the caulk to dry. Too much moisture in the caulk before drying can also cause mold and mildew growth.

It’s always best to allow your caulk to dry in a well-ventilated environment. Keep it away from rain or water, which can also cause the caulk to split. You may want to wrap some duct tape around the tube to prevent splitting, but you should be avoiding moisture and water altogether during and right after the application.

Can old caulk be caulked over?

No, you shouldn’t apply caulk over old caulk. If the previous application has already hardened or is peeling and cracking, applying a new caulk without removing the old layer will give you a thick and messy-looking job. Apply new caulk only after scraping off the old caulk using a steel putty knife.

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