How to Bend Metal Flashing

Lead Image for How to Bend Metal Flashing
  • 4-10 hours
  • Intermediate
  • 30-100
What You'll Need
20 or 40-ounce sheet flashing
Sheet metal brake
Brake mounted slitter

The type of metal flashing you are using, will determine the exact process for bending the metal. Much aluminum flashing can easily be bent by hand. However, 40 ounce of copper flashing is the best when it is bent with a machine. If you are roofing a large area, you will want to use a sheet metal brake. The metal brake will allow you to have perfect folds even along long lengths of flashing. A metal brake can be rented from your local home improvement store for not more than $100 per day. Most do-it-yourselfers won’t need the brake for much longer than that.

The actual process for bending the metal flashing is going to differ depending on the type of flashing you are making. Step flashing and drip edge flashing both require a different process, but can both be created easily with a sheet metal brake.

Step 1—Take Measurements

If you are using a sheet metal brake, you will probably purchase large sheets of metal flashing. Therefore, you will need to take measurements of the area you are trying to protect to determine the proper size of the flashing before making any bends or cuts. If you are making step flashing, you can buy it pre-cut and simply bend it on the brake.

Step 2—Cut Flashing to Width

You can actually cut the flashing once you have clamped it into place on the brake. By attaching a brake mounted slitter to the brake you can make any necessary cuts with the metal flashing already clamped down. It is best to use a scrap piece of flashing first, to make sure that your cut will be accurate. Once you are sure of the proper placement of the flashing, slide the slitter across the flashing to make the cut.

Be sure to remove the slitter before proceeding.

Step 3—Make the Necessary Bends

This is where the process will change depending on what type of flashing you are making. If you are making drip-edge flashing, you will first make the bend for the hem. In order to do this, you will slide the flashing ½ inch into the brake. You will clamp in place and lift the bending plate until it won’t go anymore.

You may have to make more than one bend depending on the type of flashing you are creating.

Step 4—Compress Any Seams

Some bends will be compressed into seams. Compressing the seams will take place after the bend has been made but before any new bends are made. If you are making drip-edge flashing, you will compress the bend that you just made at the hem. You will clamp the bent portion of the flashing into the leading edge of the clamp. Release the piece and you can see that the bend has not been made into a tightly compressed seam.