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Tutorial: How to build a Deck

5. Decking

So how many boards will you need to cover your deck?  Your deck is 10’0” deep which equals 120”.  If you divide by 6” (remember you’re using a 2x6), then you will need to buy 20 boards, right?  No, you will really need 22 boards.  Its not a 6” board but rather 5 1/2”.  This is why “nominal” versus “actual” is so important.

decking woodHow will you nail them to the deck?  If you look at the butt end of the boards, you’ll notice a semi-circular grain pattern.  What you’re looking at are the annual growth rings of the tree from which it came.   The grain orientation of your deck boards should be nailed pith down.  Another inherent problem with wood is called cupping.  This occurs across the width of a board and is more pronounced in wider boards.  The sides rise up higher than the middle thus trapping water in the cup.   In the winter, this turns to ice, which becomes potentially dangerous.  Nailing the boards with the grain facing down won’t prevent the cupping, but it will keep the ice at bay.  The cupping will be minimized because of the constant traffic on the boards pressing down against the natural tendencies of the wood.  The spacing between the deck boards should be the width of a nail.   The reasoning is because wood is a living, breathing entity. It expands and contracts depending on the amount of moisture in the air.   By the way, this is also true of the wooden floors inside your house.  By allowing some gapping between boards, you are allowing the boards room to move.  This also allows pooled water to drain through the deck to the ground below.

Begin nailing the decking at the ledger board and work out to the double header.  Lay out all the boards first to see if there are any unforeseen problems.   As each deck board crosses a joist, drive two 10d nails, about 3” apart, aligned with the joist.  Remember not to nail within 1” of the edge of a board, to use double hot-dipped galvanized nails and drive the nails into the center of the joist below.  Measure out from the house, at each end, every few boards to make sure the leading edges are an equal distance.  Because CCA lumber can no longer be used for decks, different coatings on the hardware must also be used.  The new arsenic-free alkali-based treated lumber is highly corrosive and will eat through the standard galvanized nails.  Any hardware that comes in contact with this new wood will also have a different type of coating.  Stainless steel hardware is the best but also the most expensive.  Ask your salesperson about it.  There is also hardware available that will allow you to secure the deck boards to the joists without the nails being visible.  This is just another option.

If you really want to run the decking at an angle (say 45°), then you can use any length board.   Check again with your local lumberyard and find out which lengths are cheapest.  Take the price per piece and divide it by the length. The reason why the length won’t matter is because you will be cutting the boards at 45° where they cross over a joist in order for the end to rest on a joist.  Around all four perimeter edges, the end of the decking must be flush with the outside edge of your deck.  The deck boards ending on a joist must rest on only half (about 3/4”).  The continuation of the deck board needs to use the other half of the same joist.  Be careful about nailing the two deck-ends to the same joist.   Angle the nails slightly towards the center of the joist from about 1” from the end edge of each joist.deck wood

If all of the decking is to be angled parallel, then buy boards 16’0” in length.  Why? If you do the geometry arithmetic, then you would know that your boards, after you cut them, are slightly more than 14’0” long. Now you have a different measuring problem.  Your 45° angle cuts, at each end, will be opposite to each other.  Do you need to know the longer dimension of the two edges?  No.  The ends should be flush with the outside edge of the deck.  And at the two opposite corners of your deck, the boards will get shorter and shorter.  Lay out one single deck board at 45° to your double header.   Stand at the front of your deck and hold this deck board in both hands.  You will only deal with the right-hand edge of this board.  At the opposite end from where you’re standing along the right edge, align the corner of the board with the corner of the deck.  Yes, a small part of this board is hanging over the edge of the end joist while nearly 2’0” is overhanging the double header.  Drive one nail in each end to hold the board in place.  Use the double end joist and the double header as a guide to mark the two angle cuts.  Make these two cuts then finish nailing this board in place.  Use two nails at each end and align the nails with the header and end joist.  It probably should be mentioned that a circular saw would be the fastest and easiest method of neatly cutting wood.  Additionally, there are choices to be made pertaining to the type of saw blade used.  Use a carbide-tipped blade rather than a standard blade because it will last longer.  The more “teeth” on a blade, the smoother will be the cut.  Don’t be so quick to throw away a short piece of a cut board.  Remember the corners need short pieces.  It cannot be stressed too many times that you should take your time measuring a board before you cut it.   It’s neither stupid nor a waste of time to double-check a measurement.

One you’ve installed this first deck board, it can be used as a guide for all the rest.  Cut the one end that goes up against the house, and then nail the board in place. Let it overhang the header board. Install several boards, and then draw your cut line using the header below as a guide.  Set the blade depth on the circular saw to 1 1/2” and go to it.  Finish off the rest of your deck the same way.  A file or a fine trim saw can clean up the sharp ends protruding.