A picture frame deck is a deck that has been framed using decking boards, the picture frame deck can have just a single frame or it can have a frame within a frame or even a couple of frames within a frame. If a single frame is to be used you can often double up the joists on the edges of the deck, this will support the frame enough and also the cut ends of the decking boards within the frame.

Picture frame deck frame

When building a picture frame deck that is having more than one frame around the deck it is a good idea to position the decking joists similar to this diagram.

Picture frame diagonal decking pattern

The deck boards can be positioned in the deck frame diagonally as in this picture or they can be straight. Positioning the joists diagonally is much harder and requires lots of accurate cuts.

Once the decking frame has been built you can start to build the picture frame, this is done by measuring the deck on all 4 sides, it is critical that the deck is completely square or making the mitre cuts in the corners and fitting the boards correctly is going to be difficult.

If the deck is slightly out of square you can often compensate for it by having one length of a deck board or a corner over hanging the deck slightly.

• Start by finding the longest edge on the deck and then cut two exactly identical pieces and mitre the ends at 45 degrees.
• Now cut two identical pieces for the shorter edges on the deck and mitre the ends.
• Place all the pieces on the deck in the correct positions and then start to join each corner together, a good way of doing this is by using a biscuit joiner and some external wood glue. Also use a long rust proof screw to reinforce the joints. Do this at all 4 corners!
• Now you have a large picture frame where all 4 sides should be perpendicular to each other.  Carefully move the frame to the correct position and screw it down to the joists using rust proof decking screws.

Now you need to calculate how many boards you will need to fit between the picture frame, to do this divide the gap between the two sides by the width of the decking boards + the expansion gap

If you are laying the decking boards straight you can now cut all boards to the correct length (remembering to leave the expansion gap) and place them in the picture frame.

You can then space out the boards using glazing packers or shims of the correct thickness to fill the picture frame up.

It might take a few attempts to get this perfect but changing the gap between each board by 1mm can make a huge difference to the spacing out of the boards.

Once all boards are spaced out correctly you can then screw them into position using rust proof decking screws.