Once you caulk, you can’t stop
Like most things, caulk weakens as it ages, sometimes cracking and leading to small gaps and leaks that expose your home to heat and drafts. These tiny fissures may not seem like a big deal, but they can result in higher energy bills and a less cozy space.
Re-caulking your windows is a simple springtime home project you can tackle on a weekend afternoon that will make a significant difference in your home’s ability to stay cool or warm, depending on the season. If you’re ready to get started, read on to learn how to caulk windows for a tighter seal.
If done correctly, caulking a window can prevent air leaks and make your window more efficient, but not all caulk is created equal. Depending on the location of your windows, you will need a specific kind of caulk.
Acrylic latex caulk is water-based, so it contains fewer chemicals than other types, making it perfect for interior windows.
Siliconized latex caulk contains silanes, a kind of silicone. It is similar to acrylic latex caulk but better withstands sun and other extreme weather, making it one of the best types of caulk for exterior windows.
Silicone caulk is moisture and mildew-resistant, making it appropriate for high-humidity rooms, like baths and kitchens. You’ll find two varieties: acid-cure and neutral-cure. Acid-cure caulk is best for non-porous surfaces such as glass, while neutral-cure caulk is better for wood, metal, plastic, and vinyl siding.
Polyurethane caulks are solvent-based (vs. water-based). They’re very strong and can be used to caulk between masonry siding and windows like you might find in your basement.
You’re not just caulking inside the house. You’ll need to caulk windows from the exterior, too. Make sure to choose a caulk made specifically for exterior use when caulking the outside of windows since this caulk will need to withstand water and sunlight. For interiors, you may want an acrylic caulk, especially one you can paint over.
If the caulk on the outside of your windows needs fixing, extreme weather can affect your application and finish. The best time to caulk the exterior of a window is when the weather is mild—ideally, between 50 and 80 degrees Fahrenheit. A day without extreme heat or cold will stop the caulk from melting or freezing as you work with it. In addition, don’t caulk on a rainy day (or on a day with high humidity); the moisture in the air can prevent the caulk from hardening correctly.
Don’t caulk over the old caulk! If you do, you’ll be wasting money because the old caulk will take the new caulk with it as it continues to pull away from the window. Instead, scrape away any old caulk around your window frame, and use a caulk softener if necessary (just let it soak for a few hours, then scrape the residue off with a steel putty knife).
Once you have removed the old caulk, clean the area with warm water or a gentle cleaning solution and a damp sponge or soft rag. Go over the area once more with a dry rag to remove any moisture, and wait until the surface is completely dry before you begin the caulking process. The caulk requires clean, dry surfaces for it to adhere and seal well.
Once the area is clean and dry, apply painter’s tape on either side of the window seams where you plan to caulk. You might also choose to prime the windows with a paint primer before applying caulk; this is an optional step that can help the caulk better adhere to the surface. If you decide to add a paint primer, make sure to give that plenty of time to dry, about 30 minutes to 3 hours, before you add caulk. Also, be sure that the primer you choose is suitable for exterior use if you’re doing this for the outside of the windows.
Many caulk cartridges have lines that indicate where to cut them for a specific bead size. Cut the nozzle at a 45-degree angle on the line for the bead size you wish to apply. Start with a smaller bead size; you can always cut it again later to create a bigger hole. The bead size should be small enough to fit snugly in the seam you want to fill. If it’s too large or small, the caulk won’t properly seal the gap.
Place the cartridge into the caulking gun, and test the gun on an old piece of newspaper or cardboard. This is a great way to practice your technique and see if the caulk bead is large enough for the area you’re working on.
Hold the gun steady with your dominant hand and support the base of the gun, near the tip, with your other hand. Start caulking at a point furthest away from you, then drag the gun toward your body while pulling the trigger.
Now that you’ve nailed the technique, caulk your windows! Apply the bead to the seam of your window and caulk a line in a smooth, steady motion without lots of stops and starts; this will ensure a crisp, clean line and better uniformity.
However, you also don’t want to caulk in one continuous line from one side of the seam to the other or from the top of the window to the bottom. That’s because it gets hard to maneuver the caulk gun and keep a straight line. Instead, start caulking from the middle of the seam to one corner of the window. Then, start caulking again from the opposite corner until you meet the caulk in the middle of the seam for the smoothest line possible.
Dip your finger in some water and glide it over the line of caulk to smooth it out. You’re looking to flatten the bead and push it into the seams and cracks. If you get a little caulk outside of your line, just use a damp sponge or cloth to wipe it away. You can use the back of a plastic spoon, a popsicle stick, or a foam paintbrush to smooth out the caulk if you don’t want to use your fingers.
Remove any painter’s tape while the caulk is still wet.
Caulk needs at least 24 hours to dry properly; check the label on the cartridge to ensure you’re giving it enough time, as it could take as long as 72 hours. Do not touch or disturb it until it’s completely dry. After a few hours, the caulk might look dry, but don’t be tempted. It has only just started to harden, and you need to wait the full dry time for the caulk to harden all the way through.
Find more leaks and drafts in your home’s windows and caulk them up using this same process. Make sure to give each window plenty of time for the caulk to dry. This is a quick and easy way to better insulate your house (and keep those energy bills down).
Window caulking is a fairly easy project that you can accomplish between lunch and dinner, making it very DIY-friendly. That said, there are some situations where you may want to call on a pro for a leaky window or if you need them to caulk exterior windows that are difficult to reach without a ladder or other special equipment.
Talk to a local window repair specialist if you suspect your windows are in bad shape and might need replacing or if you want a thorough insulation inspection of all your doors and windows. Finally, if there are any signs of mold or mildew, it’s time to get an expert opinion.
C.E. Larusso contributed to this piece.
You should caulk your windows about every five to 10 years. But you should make sure to inspect the windows every year, typically before winter, to look for gaps or signs of failing caulk, such as cracking or peeling. If the caulk is weak, you may need to remove and replace it before it's five years old.
There are many parts of the window that you should caulk, including the seams around the frame, the trim and molding, and the window joints. Caulk will help fill small gaps that are narrower than 1/4 inch. For larger gaps, you’ll need to first add a foam backer rod before caulking, or go ahead and repair or replace the window frame.
You will need about half of a caulking cartridge to caulk one window. The average home has eight to 10 windows, so you would need about 4 or 5 cartridges to caulk every window in an average-sized house. However, you may not need to caulk all the windows at once. If just one window has a pesky draft, you may only need half of a cartridge to fill in the gaps.
