Skirts: How to Install Horizontal Skirt Supports


A deck skirt is a trim panel fitted from the bottom of the deck trim to the ground. It serves two major purposes. First, it prevents small animals, and objects crawling or being blown underneath the deck.

Both the top and bottom edges of the skirt require horizontal support. The top edge of the skirt is supported by the deck face board. A PT 2x4 strip is used to support the bottom edge along the ground. If the rail posts run to the ground, the 2x4 strip can be mounted to the face of the posts.

If the posts are cut off even with the bottom of the deck, you will need to install blocking every 4 feet to attach the support to. Cut PT 2x4 pieces to fit from the bottom of the decking to the ground. Position these blocks vertical with the top end against the back of the deck face plate, or rim joist. Attach with screws.

Sketch showing detail for installation of skirt supports around a deck.

The horizontal 2x4 skirt support board is installed parallel to the rim joist, or faceplate of the deck, so that it is level.

Skirt supports installed on a deck.

  1. Use a string level and chalk line to mark the bottom edge of the support by drawing a line on the faces of the deck posts, or blocks.
  2. Secure the bottom skirt support to the posts/blocks with screws.
  3. Cut vertical skirt sections to fit each face of the deck, using a circular saw.
  4. Cut the skirt to height first, so that the top edge will run level the bottom edge of the deck’s top trim board and the bottom edge of the skirt support.
  5. Cut one section of skirt to length to fit each face of the deck.
  6. Miter the edges of corner pieces for a tight fit.
  7. Use full sized pieces of skirt from either end, working toward the middle of long sections. Cut the center piece to fit.
  8. Fasten the deck skirt in place with nails, flush with the bottom edge of the deck’s top edge trim.
  9. Fasten the bottom edge of the skirt along the face of the lower support using nails or screws.
  10. Fasten 2x4 supports back from the bottom support of the skirt, to the deck posts underneath to make the skirt secure.

Skirting on a Slope

On a slope, install the bottom skirt support parallel to the sloping ground. Mark and cut the skirt to match the angled support. If using single side by side boards for skirting, leave a minimum of ¼ inch between boards. Space the skirt’s bottom edge ¾ inches above grade by using a standard piece of 1x4 lumber on the ground as a spacer.

Skirt Support on Tall Decks

Install skirt supports that are taller using similar techniques. On a tall deck, more support is required. If the height of the deck is over 4’, one horizontal support is required for every 4’ of height. Run braces from the lowest skirt support back to each deck post and fasten in place with screws. Frame doors into the skirt using 2x4 lumber wherever required.

Detail sketch of deck skirt support on a high deck.