How to Caulk Your Windows (2023)

By Amanda Lutz

Nov 01, 2023
Construction worker sealing window with caulk, closeup

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Window caulking is an affordable window repair project that eliminates air leaks in your installations. Such leaks cause heating and cooling systems to work harder to regulate indoor temperatures. As a result, homeowners may see their utility bills rise. 

By caulking your windows, you can reduce home energy costs and restore your windows’ efficiency. In this guide, we’ll explain how to caulk windows and what products you’ll need for the job.



Why You Should Caulk Windows

Over time, windows naturally lose their energy efficiency due to normal wear and tear. You’ll notice windows becoming draftier as the seals around the seams and trim deteriorate. As they break down, your home becomes exposed to outdoor temperatures, causing your HVAC or heating system to work harder to maintain a comfortable temperature. 

These air leaks could lead to long-term impacts on your energy bills. According to the U.S. Department of Energy (DOE), up to 30% of homeowners’ heating and cooling use comes from heat loss from drafty windows. One recommended solution is caulking your windows to eliminate air leaks and restore energy efficiency.

Caulk is a flexible material used to seal window joints, trim, seams, and other areas on your window frame less than 1/4 inch wide. Caulking blends in with your existing window design, and some varieties come tinted or can be painted to match. If you’re unsure if you need window caulking, check the current condition of your windows. Check for noticeable cracks or crumbled caulk in the window trim and seams. If you can see the light shining around your window frame or feel the wind blowing through, it’s time to seal your windows again.



Caulking vs. Replacing Windows

Caulking seals leaky windows to improve their energy efficiency. However, there are certain situations when investing in high-quality replacement windows makes more financial sense. Caulking won’t help windows with extensive damage, severe leakage, or gaps larger than 1/4 inch.

In addition, repairing windows older than 10 to 15 years won’t yield the same cost savings as purchasing newer, energy-efficient models. Although a caulking project is less expensive up-front than replacement windows, upgrading to top-quality windows will save money in the long run.



How to Prepare for Caulking

To ensure a successful caulking project, you’ll need to prepare for the task. There are different kinds of caulk available for specific windows and window locations. Choosing the wrong option could lead to an improper seal, unnecessary toxic fumes, and other issues.

Your selected project day also impacts your caulking job’s success because exterior temperatures can affect the substance. Below, we offer some guidance to ensure your project is successful.

Choose the Right Day to Caulk

A critical aspect of a successful caulking project is selecting the right day to work. Your windows must be completely dry before beginning the process; otherwise, moisture could get trapped in the caulk and cause hardening issues. In other words, don’t choose a rainy day to caulk.

In addition, you should caulk when the weather is mild, neither too hot nor cold. Cold weather could freeze the caulk, while hot temperatures could cause it to melt. Aim for a low-humidity, mild day with temperatures between 45 and 80 degrees Fahrenheit.

Obtain the Necessary Tools

Below are the tools you’ll need for your caulking project. They can be found at your local hardware store or home improvement retailer.

Purchase the Right Caulk Type

Several types of caulk are available, each with a specific purpose and chemical compound. Here’s a guide to choosing the right caulk for your home improvement project.

When shopping for window caulk, check each product’s full instructions and recommendations to ensure it’s compatible with your window materials. Check all safety precautions and directions for application.



How to Caulk Your Windows

Below is the step-by-step guide on how to caulk your windows. (Phrases such as “running a bead” or “bead” refer to applying a long caulking strip to your window.)

Step 1: Remove Old Caulk

You’ll want to create a clean, fresh seal with your new caulk, so before applying it, remove any old caulk from your windows with a utility or putty knife. Use a caulk softener for a few hours if your old caulk doesn’t easily remove. Brush away any crumbled caulk, dirt, or other debris until the surface is clean.

Step 2: Clean Your Windows

After removing the old caulk, clean the area with a gentle cleaning solution or warm water. Don’t use anything more abrasive than a damp sponge or old rag. Dry the entire area with a dry cloth to remove any remaining moisture. The surface must be completely dry before applying any caulk. 

Step 3: Prepare the Caulking Gun

To prepare your tube of caulk, you’ll need to remove the tip. Many tubes have indicator lines to help you regulate your caulk bead. Start with a smaller size and increase it later if needed. Cut your tube at a 45-degree angle to ensure a smooth application.

Then, insert the cartridge into the caulking gun and test the bead on newspaper or cardboard. Use your dominant hand to support the gun and pull the trigger while holding the base near the tip with your other hand. Keep your wrists steady and bend at your elbows to apply the caulk. Using this position ensures that you maintain the correct angle during application. 

Keep even pressure on the trigger and start your application away from your body, pulling the gun close to you as you continue the bead. Make any necessary adjustments to the tip size before you move to the next step.

Step 4: Apply Caulk to the Window Seams

Position the caulking gun in the corner of the window farthest from you and apply a smooth, steady line in the crack. Maintain a continuous bead until you reach the middle of the window. At this point, you may need to reposition the gun to finish the rest of the line. Switch to the other corner of the window, and repeat these steps until you meet the original bead of caulk. Apply caulk in all the window frame joints, including where the frame meets the wall.  

When applying vertically, start at the top corner and run the bead from top to bottom. Bend at the knees or elbows (not at the wrists) to keep a uniform bead on the sides of the windows

Step 5: Use Painter’s Tape to Guide You (Optional)

If you can’t maintain a steady grip on the gun or aren’t confident you can apply a straight line, use painter’s tape to guide your application. Apply the tape along the edges of the window seam about 1/8 inch away from the edge. Apply the bead per the previous instructions.

Step 6: Smooth the Bead of Caulk

After applying the caulk, you must smooth the bead to create an even seal. Wet your fingers in some water, and flatten the beam into the cracks. If you don’t want to use your finger, use a popsicle stick or the back of a plastic spoon instead. 

Start in the far corner and flatten the bead in 6- to 8-inch sections at a time. This method helps reduce the overflow of excess caulk out of the sides. If any excess caulk oozes out of the crack, use a putty knife to place it back in properly. When using your finger, rewet it lightly to help create an even surface.

After smoothing, check the window seams to ensure a proper application. If any areas need more caulk, reapply and smooth again. The caulk should stick to both sides of the seam or crack. Once you’re finished smoothing the caulk, carefully remove the painter’s tape, if used, to reveal a clean bead.

Step 7: Allow the Caulk to Dry

Allow the caulk to dry properly. Depending on your type of caulk, this could take several hours or a full day. Read the instructions on your caulk to determine the proper drying time. 

Areas to Avoid While Caulking

Applying caulk to certain window areas could compromise your home windows’ functionality. Avoid these areas while you complete your caulking project.



Professional vs. DIY Caulking

You don’t need advanced knowledge of windows to complete a window caulking project successfully. Many experienced do-it-yourselfers (DIYers) could complete the project in just a few hours. Remember, you must select the right caulk for your interior and exterior windows to ensure you seal your windows properly. You’ll also need to apply the caulk correctly to fix air leaks.

There are circumstances when a professional window contractor should complete the work instead. If your windows are on higher floors, you must use a ladder and other safety equipment. In addition, if your windows have further damage, such as mold, rot, cracked window panes, or other integrity issues, caulking won’t be an effective solution. Instead, consider hiring a professional window installer and opt for new windows.



Our Recommendation

Caulking helps seal windows and eliminate air leaks. Although caulking can’t repair extensive window damage, it provides a cost-saving solution for drafty windows in good condition. An experienced DIYer or a professional window repair company can complete this simple home improvement project. 

Plan to complete your project on a non-humid day that’s not too cold or too hot. Purchase the right caulk type for your interior or exterior window needs. If your window has severe damage or has gaps larger than an inch wide, window replacement is a better option.

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Window Caulking FAQ

Can I caulk windows myself?

Yes, you can caulk windows yourself, as it’s a relatively simple task with little equipment required. However, this project takes some patience and skill to master. A poor caulking job could appear messy and fail to adequately seal air leaks. You should hire a professional contractor to caulk your windows if you’re not a skilled handyperson.

When is the best time to caulk your windows?

The best time to caulk your windows is on a rainless, low-humidity day with a temperature of at least 45 degrees Fahrenheit. The mild temperature prevents the caulk from freezing or melting due to extreme weather.

Do you caulk the inside or outside of the windows?

You should caulk both the inside and outside of your windows to eliminate air leakage and improve your home’s energy efficiency. Use a caulking gun to ensure a smooth, continuous application.