Deck Building 13 - Applying the Deck Boards

Margin of Error: 1/4"

Most Common Mistakes

  1. Not using enough nails
  2. Not leaving a gap between the deck boards
  3. Not forcing bow out of crooked boards

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You are now ready to start installing your deck boards. This part of the job goes quickly and easily and is rather exciting since you really start to see your deck come together. You need to carefully consider each board you're applying to be sure there will be no unwanted marks showing. Examine each piece and try to put the most attractive pieces in the high-visibility areas. Also, look at each side of each board to make sure you know which side you want exposed. Don't forget to check to see how badly bowed the boards are. If there are a few very bad pieces, reject them outright because they will look crooked once the decking is down.

One advantage of redwood is its outstanding stability. In varying moisture conditions its shrinking or swelling is minimal. It resists warping, checking, and cupping better than other wood.

Start your decking application from the wall and work toward the yard. Be sure that the first course you apply next to the wall is made of good, straight pieces, because this course will be used as a guide, and if it is crooked, it will affect all the other courses. Also, be sure that you leave a gap between the first course and the wall so that water can drain down the wall.

If possible, purchase boards that are long enough to span the entire width of the deck, but if the deck is too wide, this may not be possible. And, even if boards are available, any lengths over 14 feet are often very crooked, in which case it would be better just to use two. If two pieces are needed, the pieces must always join directly over the center of a joist to provide a nailing surface for each piece. Never join all the courses over the same joist, as it will look like a big suture running down the deck. Stagger the joints so that every other course joins over the same joists.

Finishing nails are not recommended for use in deck construction; use double hot-dip galvanized (HDG) 16d nails instead. Hot-dip or double hot-dip galvanized (HDG) fasteners will not rust and are less expensive than both aluminum and stainless steel nails. Beware of electroplated nails, which often do rust.

Except with redwood, it is usually best to use three nails in 2x8 pieces and two nails in 2x4 and 2x6 pieces at each point where the board crosses a joist. However, on 2x4 and 2x6 redwood boards only one nail per joist can be used. Alternate these nails from one side of the board to the other. This method counters any minor tendency to cup or pull. Two nails need to be used for boards eight inches or wider, and all nails should penetrate 1 1/2” into the joists.

I recommend you use a combination square and mark a true perpendicular line across each joist so that you can place all your nails in a straight line. It takes a little more time, but you will be surprised to see how much better it looks once the deck is completed.

The process of nailing on the deck boards is rather straightforward, but there are a few things you need to know. First, be sure you always leave a gap between each course of deck boards to allow water to drain off the deck. You can stick a flat carpenter’s pencil or the shank of a 16d nail between the courses as they are applied; this should leave an adequate gap (1/8-1/4 inches).

No board is perfect, and many will have bows that need to be pulled out, which is done by forcing the bow out as you nail from one end to the other. This is why you never nail from both ends to the middle as you may trap the bow. Put in your spacer to create the needed gap and then force the board into place. It will usually straighten out if the board is not too badly bowed. Use a smooth-headed hammer and try not to scar the wood (though the first few rains will probably draw out most of the dents). Also, a pry bar can be used to force the board straight.

Usually it is easiest to place the deck boards flush with the outside edge of one of the outer joists and let them "run wild" at the other end. This way, all of the uneven ends can be cut all at once.

The only other trick to applying the decking is to drill pilot holes when nailing near the end of a board. This involves areas such as where two deck boards join together in the center of a joist and both ends must be nailed to that joist. Usually you would split the wood if you tried to nail that close to the end of a board. To avoid this, use a cordless drill to drill a pilot hole slightly smaller than the shank of the nail (use HDG finishing nails for these end nailings), and then drive the nail through it. This will prevent splitting.

Measure out from the wall every few courses to be sure all boards are equidistant from the wall as you progress, continuing until you are one course away from the end of the joists. Also, stand up and look down on the deck to be sure you are not trapping any bows in the boards and that the deck, in general, looks good as you go. Mistakes are easier to fix before the entire deck is complete.

Tip: Paint the exposed ends of the joists and deck boards with a waterproofing for added protection.