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How to Install Vinyl Siding Around Windows

Windows can make installing vinyl siding a bit tricky so you will want to learn how to install vinyl siding around windows before starting the project. As with all things involving exterior construction, you need to pay close attention to any edges and seams as they provide places where water can penetrate. Take your time when attaching siding trim around windows so that you can get perfect results. J-channels and drip edges are the two types of siding trim pieces that you will be using.

How to Install Vinyl Siding Around Windows Directions

  1. Confirm that building paper is in place beneath the window’s nailing fin.
  2. Confirm that flashing at the bottom of the window extends beyond the window’s corners. It should overlap the nailing hem of the siding course below the window.
  3. Confirm that window flashing extends 5 inches from the sides and 2 inches from the top and bottom.
  4. Cut a J-channel wide enough to go across the bottom of the window frame and the J-channels on each side of the window.
  5. Position the J-channel piece so that the bottom of the “J” touches the bottom of the frame.
  6. Mark the edges of the window frame on the J-channel.
  7. Snip the bottom edges of the J-channel up to the marks to form little tabs.
  8. Cut off the tabs.
  9. Nail the bottom J-channel below the frame.
    1. All nailing should be done with roofing nails. Leave nails a bit loose to allow for expansion.
  10. Get a piece of J-channel a few inches longer than the side of the window.
  11. Mark a 45-degree angle with the carpenter’s square from the outer edge of the J-channel up to its inner edge.
  12. Snip along the 45-degree mark.
  13. Trim straight across the nailing fin of the J-channel to where the 45-degree cut meets the inner edge.
  14. Cut off extra nailing fin but leave the tab at the back of the J-channel.
  15. Set the J-channel against the window frame and on the bottom J-channel. The 45-degree cut will form a mitered joint, and the tab will slide beneath the “J” of the bottom J-channel.
  16. Mark the side J-channel at the top edge of the window frame.
  17. Trim the side J-channel at the mark and nail in place.
  18. Repeat steps 10 through 17 for the other side.
  19. Now you need a drip edge piece of trim to continue learning how to install vinyl siding around windows.
  20. Measure and cut a drip edge the width of the window plus both J-channels along the side.
  21. Set the drip edge in place and mark where the tops of the J-channels meet the drip edge.
  22. Cut tabs from the drip edge and bend them down into the J-channels.
  23. Nail drip edge over window with tabs fitted into J-channels.
  24. Cut a J-channel piece the width of the drip edge.
  25. Cut tabs in the J-channel to fit over the drip edge tabs and into the side J-channels.
  26. Nail the top J-channel into place.
  27. As you lay courses of siding, cut them to fit around the window behind the J-channel edges.
  28. Leave 1/4 edge of space between siding pieces and J-channels to allow for expansion.

Tools & Materials

  • Hammer
  • Pencil
  • Carpenter's square
  • Utility knife
  • Tin snips
  • Measuring tape

Get Help From the Best Vinyl Siding Installers

Although you may enjoy learning how to install vinyl siding around windows, you might not have time for a big job. Siding around multiple windows or upper-story windows is quite an undertaking. PJ Fitzpatrick has specialized in installing vinyl siding on homes in Delaware, Maryland, Pennsylvania, and New Jersey for decades. Ask us for a siding estimate today.

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