The worst time to find out that you have a leaky window is during an intense rainstorm. If you can fix the issue ahead of time, you’ll save the integrity of the window as well as the wood around it. Sealing a window is quite simple when you’re using caulking.

So, do you want to know how to seal windows from water leaks? Follow these steps:

  1. Remove the old sealant with a putty knife.
  2. Wipe down the area with a dry rag.
  3. Wait for it to dry (use a tarp if it’s raining).
  4. Apply a thin bead of caulk sealant around the window.
  5. Let it dry and cure for at least 24 hours before removing the tarp.

Throughout this article, you’ll also learn what causes leaky windows, what tools and supplies you’ll need to fix yours, and when it’s time to replace an old window.

How to Seal Your Window to Prevent Water Leaks

Minor water leaks can turn into serious problems by weakening the wood around the window. Over time, a small trickle can cause an entire window frame to have wood rot, breaking it out of the wall. While it might seem excessive, this scenario is far from rare.

The importance of maintaining perfectly seal windows, especially during rainy seasons, can’t be understated. Before you start removing sealant and begin working on the window, it’s important that you have everything you need for the job.

Supplies & Prep Work

Getting the right type of caulk is important if you want your windows to stay sealed. Traditional silicone caulk is a surefire way to weaken your window frame’s seal because it can’t take the constant impact of rain, hail, snow, and direct sunlight.

Along with sealant, let’s check out all of the supplies that you need to start the job, as well as how you can get prepared to start working. Here’s everything you need to be ready:

  • You’ll need a putty knife to remove the old caulking from the area. All windows are installed with caulk around the edges, so there will almost inevitably be a few old bits that need to be removed. Putty knives are thin and long enough to take it off in sections, so try out the Qualihome Putty Knife Set to make sure that you have the right size.
  • Get a new tube of acrylic caulking sealant, like this Sashco Big Stretch High-Performance Sealant. It’s the best kind to use for windows because it can withstand the constant pressure of rain and the heat of direct sunlight. If you use silicone by itself, you’ll have to replace it once every year or two.
  • Several rags are also going to be required since you’ll need to dry the area and remove excess amounts of caulking. Never let it drip. In fact, you can use blue tape, such as ScotchBlue to prevent it from falling all over the place. Remove the tape after you apply it and you’ll be left with a smooth, straight line of caulk.
  • (Optional) Get a tarp or a canopy tent to keep the window dry for at least 24 hours after applying sealant. You don’t need to use either of them if it’s not raining outside since nothing will get it wet (aside from sprinkler systems, fountains, etc.).

A Step-by-Step Guide to Sealing Window Leaks

When you have everything you need ready to go, it’s time to start sealing the leaky window. It’s not a bad idea to put all of the supplies within arm’s reach, especially since you need to be able to act quickly with a sealant that starts to drip.

Here’s the step-by-step process of sealing windows with leaks:

  1. Take a putty knife and remove all of the old sealant. If you try to go over it with a new tube, you’ll still have the same poor foundation sitting underneath. It’ll start to crumble and you’ll be left with the same situation that you tried to repair. Always use a putty knife at a 25-degree angle.
  2. Use a dry rag to wipe down the area where you’ll be applying the sealant. Moisture is the enemy of caulking that needs to cure, so using rubbing alcohol is a good idea. The combination of alcohol and a rag with be more than enough to prepare the area for a new layer of caulk.
  3. Wait for it to dry. This process may take up to 24 hours, especially if you live in a humid area. Remember that you’ll have to replace the interior and exterior caulk since you don’t want to have to go back and repeat the same process later on in the year. Use fans or tarps to protect the edges from moisture.
  4. Use acrylic caulk to apply a thin bead along the edges of the window frame. Don’t forget to use blue tape if you want an accurate placement from end to end. Repeat this step on the inside and outside, ensuring that the lines of tape are even and level. Also, don’t add too much caulking. It should be just big enough to cover the entire crack.
  5. Keep the tarp or umbrella over the sealant until it dries. This process usually takes about 24 hours. Even if it feels dry on the outside, the core of the bead will take a day or so to cure completely and bond with the window frame. Again, using fans and blowdryers is a great way to speed up the drying process.

Why Does Your Window Still Leak After Replacing the Sealant?

If your window still leaks after you’ve applied the silicone caulking around the edges, then something wasn’t done properly. Either the foundation was incorrect or you didn’t allow for enough time before the bead got wet from rain or humidity.

Regardless of the result, let’s check out why your window might still leak after you’ve applied a new sealant:

  • Your window might have a small crack that you don’t see. It doesn’t matter how well you apply the sealant, none of it will fix a cracked window. Cracked windows are the cause of leaks more often than not. Rocks, roughhousing, and all sorts of other mishaps can cause cracks that are too small to notice right away.
  • There might’ve been gaps in your work. If you applied the caulk too quickly, then there’s a chance that holes formed. When caulk starts to dip into the cracks of a window, you need to add another layer to level it out sometimes. If you forget to, you’ll end up with a porous sealant that does you no good at all. Always double check your work!
  • If you don’t remove all of the excess old sealant around the edges before you apply a new layer, you’ll undoubtedly run into trouble. It might start leaking right away or in a year, but layering over old caulking is never a good idea. Thoroughly check the window frame before you start using a new tube.
  • Loose windows cause problems as well. If your window isn’t held in the frame very well or if the wood is rotting away, a simple bead of sealant won’t change anything. It might limit the amount of water coming through, but you’ll have to deal with leaks no matter what. Unfortunately, a new window frame is the only fix for this issue.

What Causes Window Leaks During Rain Storms?

Leaky windows are a pain to deal with no matter what. However, if you’re able to figure out what’s causing it, you can prevent it from showing up. With that being said, all sealant has a limited lifespan.

Caulk usually lasts for about 5 years, so don’t expect much more than that. Below, you’ll find the five main causes of leaky windows:

  • The main cause of a leaky window is loose sealant. As mentioned throughout this article, you have to replace and maintain caulking by following the steps above. Old sealant dries, crumbles, and falls off of your window. Without proper sealant, leaks are bound to show up.
  • Using the wrong type of caulk can also cause all sorts of issues right away. Acrylic caulk is the best kind to use for windows and other outdoor purposes, so stick with it if you have the opportunity. Traditional silicone and low-quality caulk can break apart and loosen from the window frame.
  • Single-pane windows allow water to get through much easier because they provide less of a barrier. Double-pain windows have more durability and structure, so they don’t crack as easily. They also have infinitely better insulation, so there are more than enough reasons to upgrade.
  • As mentioned in the previous section, cracked windows are another common cause of leaky windows during rainstorms. They’re made much worse with heavy winds and as time goes on, so it’s best to repair the crack with a resin material as soon as possible. You’ll save yourself tons of money, too!
  • If you bump any window hard enough, the caulk could lose its seal. You might not notice anything by looking at it, but water will start to pour through to the other side. Unfortunately, you might have to repair the sealant much sooner than you initially thought.

As you can see, there are a plethora of causes for leaky windows. Luckily, you now have the knowledge that you need to repair such issues. That being said, you probably don’t want to have to remove the entire strip of sealant if you don’t have to. For patchwork suggestions, proceed to the next section.

How to Patch Old Window Caulking

If you have windows that are partially exposed to sunlight whereas the tops aren’t, then there’s a high chance that the bottom portion will crack first. When it does, you might be tempted to replace the whole deal.

The good news is that you can patch window seals by using caulking, rubbing alcohol, and blue tape. You don’t need to spend hours doing it either. In fact, a simple reapplication can take as little as 10 minutes if you know what you’re doing.

Follow the instructions below to patch your window’s sealant:

  1. Start by using the same putty knife mentioned in the first section. Make sure that you don’t remove any caulking that’s not damaged. Consider putting blue tape over the areas that you don’t want to replace.
  2. Next, use rubbing alcohol or dish soap to clean the surface. This step is crucial to prevent the caulking from loosening too quickly. Wait for it to dry for a few hours or use a fan to speed up the drying process.
  3. Use a brand-new tube of acrylic caulk to seal the window. Overlap the old sealant that’s staying behind so there aren’t any gaps. You can scrape off any excess caulk later on, but right now it’s important to prevent holes from forming.
  4. Remove the blue tape once you’ve finished applying the new sealant. Don’t remove it too quickly or it might fling some of the sealant all over the window. Wait for at least 24 hours for it to dry and cure before you put any pressure on the window.

The most important part of this whole repair process is that you overlap and connect the old caulking to the new bead that you’re applying. By following these four steps, you’ll be able to stretch out the time between redoing the entire window’s sealing.

When Is It Time to Replace a Leaky Window?

If you know what the cause is, then you’ll be able to find a solution in no time. As mentioned previously, the window itself might be the issue.

The average window in a home lasts between 15 to 20 years before it needs to be replaced. If you take proper care of your windows by cleaning them and replacing the sealant every five years while doing repair patches in between, then you don’t have to worry about anything else.

Unfortunately, improper care and neglect can cause windows to break easier. If you don’t reseal as often as you should, then cracks will form and the glass will become less durable. As moisture gets in, mold will form and the wood surrounding the window will rot.

Even by simply cleaning your windows regularly with cleaner, you’ll prevent it from cracking. Dust and dirt that build up cause heat to roast your windows quite literally! Try to make it a routine to wipe down your windows at least twice a month (once a week is best).

Finally, you might consider replacing your windows if they don’t keep out the outside temperature. Single-pane windows are terrible for insulation, but some windows have thinner glass than others. If you want to upgrade, you’ll improve the integrity of your windows and lengthen the time between sealant applications.


When your window leaks during a rainstorm, it can cause all sorts of issues. Not only does it give you a headache, but it can invite mold, termites, and wood rot. By reapplying sealant, keeping your windows clean, and patching it when you need to, you’ll be able to maintain a dry environment around the window frames of your home.

Here’s a quick recap:

  • Rags, rubbing alcohol, sealant, dish soap, and a putty knife are all you need to seal your windows.
  • Make sure you use acrylic caulk rather than silicone since it’s designed for outdoor applications.
  • Always apply caulking inside and outside of each window.

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