Two Ways to Install Sill Pan Flashing With ZIP System Tape

April 13, 2019


ZIP System tape logo

Because ZIP System® Stretch Tape stretches in all directions, you only need one piece to cover a standard sill

This is part one of the three-part series on window installation. The other parts cover Installing the window and flashing the jambs, and Installing head flashing.


Step by step:

  • Measure sill, add 12 inches to measurement, and cut the tap to that length. This allows the tape to fold up the jambs 6 inches on each side.
  • Fold the tape 2 inches down the face of the wall. For 2x4 walls, use 6 inch tape. for 2x6 walls, use 9 inch tape.
  • ZIP System Stretch Tape can be repositioned during assembly, if needed.
  • Use J-roller to seal flashing to sheathing. Focus on wrinkles or air pockets, which can become 'fish-mouths', which can allow water to creep in.


Video 2: Install Sill Pan Flashing With Standard 3 Inch ZIP System Tape

A specialty tool makes placing non-stretch tape in corners easier


To create window-pan flashing using standard 3 ¾ inch ZIP System tape, it’s easiest to cut each piece one at a time. 


Install the corner pieces

  • First, cut one 3-inch strip from the roll of linerless tape and place it into one of the bottom corners, with 2 inches hanging out past the face of the ZIP System sheathing.
  • Seal the tape to the rough opening, using the zip system corner tool or similar device.
  • Using your fingertips, slowly start working the overhanging tape down onto the face of the panel. Wrinkles in this part of the tape are normal.
  • Repeat this process for the opposite corner. 


Apply the outer sill flashing

The next piece we are going to install is the piece that lays across the bottom. This piece will go across the entire bottom of the rough opening and at least two inches of each side. Attach this strip so that two inches of the tape surface will wrap around the ZIP System surface.

  • Attach the end of the tape roll at least two inches up the rough opening, and roll out the tape.
  • Make sure the tape is seated in with the corner of the rough opening by using the ZIP System corner tool or similar device.
  • Lay into place, making sure you have two inches of overhang past the sheathing surface.
  • Using the ZIP System corner tool, press the tape into the remaining corner and attach the tape to the side of the opening.
  • Cut the tape at least two inches above the rough opening corner.
  • Next, make a small vertical cut in the tape at each corner. No need to be precise — the tape will stretch.
  • Fold the tape over the rough opening onto the surface of the zip system sheathing. 


Seal the corners

Next, install two 8-inch strips in each corner. Each piece should extend six inches up the jamb and two inches across the sill.

  • Install each piece, making sure the tape overhangs the sheathing by two inches.
  • Seat the tape into the corners, using the ZIP System corner tool or similar device.
  • Make a small horizontal cut in the tape at the corner of the window. No need to be precise — the tape will stretch.
  • Then, fold the tape over the rough opening onto the surface of the ZIP System sheathing. 


Apply the inner sill flashing

Now install a final piece of tape that covers the sill and six inches up each jamb. It should overlap the previous pieces by a minimum of one inch. In a 2x4 wall, this piece will end up flush with the interior side of the rough opening. As before, use the ZIP System corner tool or similar device to seat the tape well into the corner. 

Finally, go over the entire taped portion of the opening with the ZIP System roller to ensure a good adhesion to the rough opening and the ZIP System surface. 


—These videos are provided by ZIP System®, one of ProTradeCraft’s advertisers. A next-generation exterior roof and wall solution, ZIP System streamlines the weatherization process with an integrated water-resistive barrier and taped seams replacing the need for house wrap or felt, while eliminating the risk of trapped water between sheathing and barrier and protecting against air leakage. View all Zip System's content