How to Picture Frame a Deck

Installing blocking is the most important step, and the main difference between framing a picture frame deck and a standard deck. You will need to add two extra joists on each side of the deck: one to support the inner edge of the border board, and one to support the ends of the infill boards. There is no need for additional blocking on the outside edge of the deck where the band/rim joist is located. The space separating the additional joists depends on how far you want your border board to overhang (more on this below). If your deck includes wood posts, install the posts and post blocking first. 

Step 1: Install the First Joist

Install the blocking joist located nearest the outside joist first. To accommodate the deck board screws, align it so the center of the joist is about 1 in. in from the inner edge of the border board. Because of the close proximity of this additional joist to the outside joist, you won’t have access to both sides of the board, which means you won’t be able to install standard joist hangers at the ledger or rim joist. Here is one option to secure the first additional joist: Fasten blocks of the proper thickness at various lengths down the inside of the existing joist, and then fasten the new joist to the blocks. Finally, secure the new joist to the rim joist and ledger using structural angle brackets. 

Step 2: Install the Second Joist

Attach the second, inner joist to the first joist, using the same methods in Step 1. Position it so the center of this joist is about 1 inch in from the end of the infill deck boards. If you plan to have your border board overhang, you might skip the blocks and connect the two blocking joists side by side.

Step 3: Protect Framing with Flashing Tape

Once you’ve added the two extra joists to both sides of the deck, protect the top of all the joists, blocking and stair framing with Trex Protect™ flashing tape. Trex Protect will add life to your deck by protecting the top of the framing lumber from standing water and will prevent water from penetrating the wood by creating a seal around the fasteners. 

Installing the picture frame boards before the infill boards will make it easier to achieve the perfect spacing between the border and infill boards. And remember to use square-edge Trex composite deck boards, not grooved, to picture frame your deck. 

Step 1: Install Fascia or Spacing Alignment Blocks

Aligning your border boards flush with the fascia gives your deck a modern look. Follow these steps for the best results:

1. Install the Fascia First: Use this as a guide for your border boards.

2. Overhang Option: If you prefer an overhang, attach temporary alignment blocks at the top edge of the joists. This ensures consistent overhang across your deck.

3. Measure for Overhang: Trex Composite Fascia Boards are over 1/2 in. thick. Cut blocks to 1-1/4 in. for an overhang of just under 3/4 in.

4. Cut and Install Blocks: Rip blocks from scrap lumber. Secure them with screws at both deck corners and every 3 to 4 ft. in between.

Step 2: Notch Around Posts (if necessary)

If your border boards need to be cut around railing posts, it’s easier to do this before you cut the miters at the ends. Simply set a border board that is longer than you need on both ends, lean it up against the posts, and mark the post locations on the board. Measure from the alignment blocks to the posts to determine the amount that needs to be cut out of the border board. Cut the notches in the border board with a jigsaw. Adding an extra 1/4-inch space around the posts will make the board easier to install and allow for expansion and contraction. That space will be concealed when you install the post-base trim. 

Step 3: Mark and Cut the Miters

Once you’ve cut the notches for the posts, slide the border board into position and flush with the fascia or alignment blocks, then mark the location of the miters with a speed/rafter square. When you measure, make sure to include a gap between the two intersecting miter boards. The size of the gap depends on the outdoor temperature at the time of installation. Leave a 1/8-in. gap if the temp is greater than 40 degrees F, and leave a gap of 3/16 in. if the temp is higher than 40 degrees F. Cut the miters with a miter saw or a circular saw with a sharp blade. Find out more about cutting composite deck boards here.

Step 4: Fasten the Border Boards

With the border boards cut to size, predrill the holes and install two fasteners every 16 in. about 1 in. from each edge of the boards. You can secure the border boards with Trex Hideaway Composite Deck Screws or the Trex Hideaway Decking Plug System, which features screw hole plugs made from the same shell material as the decking, making them nearly invisible.

Install the first infill board at the outer edge of the deck, so if the last board needs to be ripped down to size, the cut side will butt against the house and possibly be hidden by flashing.

Step 1: Cut and Install the First Board

Cut the first and the subsequent infill boards, so there is a gap between the infill boards and border boards. Just as you did with the two-mitered border boards, leave a 1/8-inch gap at each end if the temp is greater than 40 degrees F, and gaps of 3/16 inch. if the temp is higher than 40 degrees F. Install fasteners at each joist location on each side of the board. Even if you are using Trex Hideaway Universal Hidden Fasteners, you will need to secure the side of the first infill board nearest to the border board with Trex Starter Clips, composite screws, or screws and plugs.

Step 2: Install the Center Infill Boards

The infill boards are installed like any Trex composite deck boards. Make sure to follow the recommended installation procedure for the fastener you are using. Given the long lengths of deck boards and the inconsistencies in lumber dimensions, it’s fairly common for projects like decks to have variations. Before you cut all the deck boards at the same size, check to see that the space between the parallel border boards is the same down the length of the borders. If the length varies, you will have to cut your infill boards to accommodate the changes. Double-check that the gap is consistent on both ends before fastening each board. For long decks, it’s always a good idea to run a string or snap a chalk line every few rows as a reference to make sure you are installing the infill boards in a perfectly straight line.

Step 3: Install the Last Infill Board

If necessary, use a circular saw or table saw with a sharp blade to rip the last deck board to width. To secure the side of the board closest to the house, you will need to use either composite screws, or screws and plugs.