How to Repair Window & Door Flashing

Slip a vinyl zip tool under the lowest piece of vinyl near the window or doorway. The zip tool unlocks the piece of vinyl from the one below it so you can remove the vinyl piece. Once one piece is out, remove all the other pieces around the window or door.

Cut a roll of 10-inch flashing into 5-inch strips, using tin snips. Cut a 5-inch piece so it is the width of the window or door, plus 3 to 4 inches to go on either side of the window or door. If you are flashing the door, you don’t need to put flashing under it.

Remove the nails holding the bottom of the window in position, using a pry bar. Slide the flashing under the window so the top is directly under the window. The bottom of the flashing should be even with the bottom of the nailing hem on the piece of vinyl underneath it. Trim the flashing with tin snips if necessary to get it the proper width. Replace the nails through the window and into the flashing and the sheathing.

Cover the subfloor and any exposed wood on the door’s opening with flexible adhesive flashing tape. Cut the flashing to the correct length. Pull off the adhesive backing as you place the flashing directly on the wood’s surface. Cut smaller pieces, as necessary, to create a seal and to ensure water runs down and away from the door’s corners.

Remove nails on both sides of the window or door. Slide a 5-inch-wide piece of flashing into the space. Extend the flashing at least 2 inches above and below the door or window. Lap the sides over the bottom horizontal piece of flashing. Replace the nails.

Cut a slit in the building paper in a horizontal line 2 inches above the window or door, using a utility knife. Remove nails from the top of the door or window. Slide a piece of 5-inch flashing under the building paper and above the door or window. Overlap the flashing on either side with the horizontal piece. Replace the nails in the door or window. Add roofing nails to the top corners of this piece of flashing.

Inspect the flashing. Imagine water running down the wall. If you see any spot where water runs anywhere but down, rearrange the flashing to redirect the water.

Reattach the vinyl siding piece. Start at the bottom and work up. When you get to the last connection, use the zip tool to help you reconnect the two pieces of siding.

Examine the reattached vinyl siding for any gaps along the window or door. If gaps exist, run a bead of silicone caulking in them to seal out any water that might otherwise seep in.