How to Fasten Deck Boards to a Joist System

Jim Mallery

This is Part 9 of 9 in our Series on Restoring Wood Decks and Building New Wood Decks. Navigate to the first article: Restoring a Wood Deck

With your joists installed, here are some final tips for deck construction. Even if you are paying someone else to build your deck, some of these are good to know to monitor your contractor's work.

Decked Out: Finishing Touches

  • Ledger Board. The board should be pressure-treated. You'll want to flash the top so that water does not get behind the board. You can buy preformed aluminum flashing for this purpose. You also can buy adhesive membrane to put over the face of the ledger to protect it from water. The ledger should be attached to the rim joist of your house with 3-inch lag screws (3/8") and washers, 16 inches on center and staggered up and down.
  • Wear the Crown. Your boards will have a crown--one side convex and the other concave. Put the convex side up, so the water will run off the board. Even some composite boards have a slight crown.
  • Spacing. Use a spacer to create a uniform spacing between boards. Nails (16d) or strips of wood ripped to the width of your desired spacing will work fine. Trex provides a tool, shaped like a speed square, that gives proper spacing.
  • Beveled Ends. Some builders will use a special technique to butt boards over a joist. They will bevel the end of each board at 45 degrees so that the angle of one board slips under the angle of the other. They will then drill the top board (to reduce the chance of splitting) and nail it to the joist. The nails will pass through the bottom board, holding both boards firmly. The method takes a little more work, but it gives a cleaner-looking joint.
  • Knots. As you lay boards across the joists, look for knots in the joist that impede nailing or screwing. Sometimes they are impenetrable. Set your board in place and drill holes through the board and into the knotted joist where the nails will go. Then pull the board back and finish drilling into the joist. Use a bit sized to make the nail snug, or almost the exact size of the screw. Don't think you can muscle through the knot without drilling--the nail will bend and the screw will break.
  • Membrane. Check with your lumberyard to see if they carry any of the waterproof membranes that adhere to the top of the joist. The membrane will seal around nails and screws to prevent water from seeping into the joist. The protection will add decades to the life of the joist.
  • Black Top. Painting the tops of your joists with black porch paint will reduce the visibility of the joists as you stand on the deck. It's an aesthetic thing that gives a cleaner look to the deck.

This concludes our series on Deck Repair. These finishing tips will help you construct a strong, long-lasting deck that will provide years of outdoor enjoyment.

Next Step: Have a cold drink, and get on with planting a small garden.


About the Author

Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing, and rebuilding homes.

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