How to Wrap a Window Corner Sill with Aluminum Coil

Lead Image
  • 2-6 hours
  • Intermediate
  • 100-200
What You'll Need
Coil Stock
Coil Dispenser
Siding Brake
Measuring Tape

When you decide to wrap a window with an aluminum coil, there are a few things that you will need to keep in mind. You will find that once you are able to figure out the necessary tips and tricks and have the necessary hardware you will be able to wrap your window sill with aluminum coil easily and quickly.


You will need to begin this project by measuring your window sill. You will need to be sure to add about 3 inches to the width of your window sill. This will help to add an extra 1 1/2-inches on either side of the sill. You will need this for later on whenever you make your corner caps. Whenever you measure the 3 sides of your sill you will need to be sure that you add about 1/8-inch to each of your measurements. You will need to do this to the face as well as the top and underside of your sill. Once you have all of your measurements, you will need to add all of them up. This will give you the full piece of aluminum that you will need to begin with.

Transfer Measurements

You will need to transfer your measurements as you use the coil stock and your brake. You will need to be sure that the aluminum does not fit tightly around the sill. It will need to have an overall loose fit to it.


You will need to do the exact same thing for the frame of your window. You will more than likely need to go through a few pieces until you get a feel for the process. For the perfect fit, you will need to make bend tabs as well as relief cuts.

Corner Caps

In order to make corner caps, you will need to hold the sill cap made of aluminum up to the actual window sill. As you do this, you will need to mark each end of the sill and then cut each of the slits up to the marks you have already made. Once you have done this, you are going to create a box with these tabs by bending them over the sill.

What to Prevent

It is important to know what it is that you are looking to prevent whenever you are doing this. You will find that if it is not done correctly you will have a lot of problems with moisture. This is because the wall cavity will become exposed and all of the outside moisture will be able to get in. If this is done correctly, you will find that your windows will become much more durable. If this is not done correctly, then it could jeopardize the warranty of your windows. Remember that the windows are what stands between your home and the outside elements. You will need to be sure that you are able to properly protect your home.