Replacing Window Flashing

A woman points to a window.
  • 2-10 hours
  • Intermediate
  • 0-500
What You'll Need
Safety goggles
Metal snips
Tape measure
Rubber gloves
Pry bar
Nail puller
Putty knife
Silicone sealant
Aluminum flashing
Nail set
Spray bottle
Wood putty

If you notice your window flashing isn’t holding up, it’s imperative that it gets replaced quickly. Allowing damaged flashing to remain can end up causing severe damage to both the window and the homes structure. Replacing flashing may be time-consuming, but as long as you follow the directions you can do this yourself.

Step 1 - Remove Old Flashing

The first thing you will need to do is remove the old flashing. This is going to require you to pull back on the siding to expose the flashing. Removing the first panel of siding will actually work a lot better and make the job a lot easier, albeit time-consuming. Place the siding panel to the side so it won’t become damaged.

Use your nail puller to take the nails out of the flashing. With the nails out, you will need to scrape the sealant or caulking away with your putty knife. Try to remove as much as this as you can.

Make a mix of bleach and water and put it in the spray bottle. Wearing rubber gloves and goggles, spray this mixture on to the casing. This will help remove any dirt and debris that has been left behind.

Step 2 - Prepare the New Flashing

Measure out the new flashing and cut it to size. Make sure you are wearing your work gloves when you do this. The flashing needs to hang over about a half-inch on each side, so allow for this in your cutting.

Place a thin line of the silicone sealer on to the edge of the window. This will help prevent water from running down into the casing and siding. This is important because any water that is allowed to run in can cause severe damage to the structure of your home.

Step 3 - Install New Flashing

You are now ready to install the new flashing. You can slide the new flashing underneath the area where you removed the siding panel earlier. Try to use the holes that are already there to nail the flashing in. Use a nail set to sink the nails for security.

If you have any nail holes left you can fill these in with wood putty. Once the putty has dried, you can use your sandpaper to sand it down.

Step 4 - Replace Siding

You’re ready to replace the siding panel that you had to remove earlier. As long as you were careful you won’t need to worry about replacing this, you can just use the same piece that was previously there.

Your new flashing is now installed. As long as you have taken your time with this and followed all the instructions, it should work perfectly. If you notice any problems with it you will want to fix it as soon as you notice it. Flashing is not something that should be left damaged as it can seriously cause extreme damage to your structure.