A window sill, also known as a window ledge is located at the bottom of the window (both inside and outside). It is an important part of a window as it holds the window in place and provides support to its structure. In addition, also protects the wall from water as it directs the rain away from the wall. That’s why window sills are angled. Another great benefit of a window sill is that it serves as a great place for showcasing decoration pieces, plants, flower vases or candles, etc.

Having a window sill is not an option, rather it is a necessity. They have been a part of windows from Egyptian times and they are still used for the design and functionality of modern windows.

Given the importance of a window sill, it’s essential to keep an eye on its condition and replace it immediately if it is rotting. In most cases, you can see the sill rotting but if you’re not sure whether it is rotten, you can touch it and if it feels soft, it means it is rotting or is rotten. Another sign of a rotten window sill is that it gets discolored because rotten sills usually have mold or fungus, which changes the color of the sill. You can also replace your window sill to give it a new look.

Once you’ve figured out that your sill is rotten, the next obvious step is to replace it. In this article, we’ll show you the steps to replace a window sill. But first, let’s discuss the different types of window sills.

Types of Window Sill

Here are some of the most common types of window sills:

Steps to Replace a Window Sill

You can replace a window sill on your own or you can call a professional. If you choose to replace your window sill by yourself make sure you have the right tools and you also need to follow the steps to replace a sill properly.

Below is a quick tutorial on how to replace a wooden window sill on your own.

What you’ll need:

Step 1:

Start by removing the interior casing molding to remove the stool. Some stools are straight while others are rabbeted. Rabbeted stools usually overlap the window sill you’re your window has a straight stool, you need to remove it from the inside using a pry bar. But if you have a rabbeted stool, you need to remove it from the outside. 

Step 2:

Next, cut the sill into three pieces using a handsaw. Then remove the pieces from the window using a flat pry bar. Remember to remove the middle piece first and then the side pieces. While you’re removing the sill, nails from each side of the window will come out. To pull them out, you can use slip-joint pliers.

Step 3:

Now, take a piece of lumber and place the three pieces of your old sill that you removed from your window on the lumber. Then mark the lumber accordingly and cut it. Since the sill is beveled, you need to cut the lumber accordingly using a circular saw. One thing to keep in mind is that if your old still is too much rotted, you cannot use it to mark your new sill and measure its width, thickness, and length.

Step 4:

Next, install the new sill by pushing it into the jamb grooves on each side of the window. Remember to protect your sill with scarp lumber when you’re tapping it into place. To make sure that the sill sits firmly on the framing, you can insert shims under the window sill.

Step 5:

Now secure the sill in place by using a drill. Next, insert a nail into the sill from the top using a hammer. Make sure that the nails go into the framing below.

Step 6:

Next, caulk the joints to fill in gaps. It’s very important to apply the caulking correctly otherwise water can seep into the sill, which can damage it.

Step 7:

Finally, paint the sill. To do so, first sand flat areas of the sill and then apply primer. Next, sand the primer and finally paint the sill with the color that matches your window.

How to Prevent a Window Sill from Rotting

Although you can replace your window sill when it’s rotten, it’s best to take measures to prevent it from rotting in the first place. The first thing to do is to clean your sill with soapy water twice a year. If the sill has mildew, you can make a mixture of water and vinegar and spray it on the mold directly. Once you spray the mixture, let it sit, then wipe it and let it dry. Finally, clean the sill with soapy water. If your sill develops water sports, you can use distilled water to clean them.


A window still is one of the main parts of any window. Not only does it hold the window in place and provide structural support but it also protects your wall from water. However, since window sills are exposed to rain, they can rot and need to be changed frequently. You can replace your window sill on your own given that you have the required tools. If you want to replace your window sill, you can follow the steps we have discussed in this article. But if you don’t feel confident about replace your window sill or you’re finding it difficult to replace your window sill, you can always call a professional like Kettle Contracting.

Kettle Contracting is a home renovation and home remodeling company that offers a wide range of services, including interior exterior caulking, home painting, window, and door installation, and more. The Window Caulking Experts at Kettle Contracting make sure there are no gaps in your window and they can change your window sills quickly and without causing any damage to your window. Whether you’re looking for Brick Window Sill Replacement or you want to replace wooden, stone, or tile sill, Kettle Contracting is there for you. So, if you want the help of professionals for replacing your window sills, contact Kettle Contracting today!

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