Deck Building 14 - Attaching the Two Outer Joists Deck Building 14 - Attaching the Two Outer Joists

Margin of Error: 1/4”

Most Common Mistakes

  1. Not cutting square ends.

As you begin to apply the last deck boards, a final adjustment can be made. What you are striving for is that the outer edge of the last course of decking boards be exactly flush with the ends of the joists. Some builders don’t bother with this, but it adds a nice finished look. The only way to make this work out is to cut the joists after the next-to-the-last course but before the last course is nailed on. This way, you can tell exactly how things are going to work out. After the next-to-the-last course is in place, measure to the ends of the joists for their final cut. The measurement is made from the outer edge of the next to the last course to a point on the joists that equals the gap between courses plus the width of a deck board (say, a 1/4" gap with a 5 1/2” board measures 5 3/4”).

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Then mark the ends of the joists at this point and draw a line across them with a combination square. Now you can cut the joists at this point, install the final course of deck boards, and have a perfect fit. Be sure you make good, straight cuts so the band will fit on properly. After you have cut all the ends of the joists you can install your last course of deck boards. Again, be sure this is a good, straight course, since it will be more visible than the others. After this last course is in place you can install the band joist (the piece that is installed across the ends of all the joists). Often this band joist is one size wider than the joist, to act as a curb for the decking.

Now you are ready to cut the “wild end” of the deck boards. To do this, make a mark at either end of the deck and pop a chalk line to get a perfectly straight cut. Cut off the wild ends of the decking boards to this line. Be sure your marks are where you want them to be, remembering if you are designing in any cantilever over the joists.

Set your saw to cut through the deck boards plus 1/4” and start cutting. Stop and check every now and then to be sure you are on line and not veering into or away from the joists.

It is a good idea to paint the exposed ends of the joists and deck boards with a waterproofing for added protection.

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