Building a deck remains one of those perennial favorite projects. A well-built deck definitely adds to the enjoyment of your home, while also adding resale value. With a few carpentry skills and tools, the construction of a basic — or even not so basic — deck is something that’s well within the reach of most home improvement do-it-yourselfers. And there’s something about that combination of fresh air and fresh sawdust that’s irresistible!
Every deck, no matter the size, style or complexity, consists of two basic components — the underframing (including the foundation) and the decking. If the deck sits up off the ground very much, you can add two additional components as well — a railing and a set of stairs.
As with any home improvement project, construction begins on paper. Whether you do the design yourself or enlist the aid of a designer, lumberyard or home center, the design needs to incorporate all of the structural elements such as the size and layout of the support piers and framing lumber. If your deck will have stairs and a railing, that design should be included as well.
FOUNDATION AND UNDERFRAMING
This is the structure that supports and braces the load of the deck and its occupants, and while it’s rarely seen, it’s actually the most important part of the entire structure. Due to its location, where it’s in close proximity to the ground and also subject to water runoff from the deck above, pressure-treated lumber is typically the best choice for this part of the project.
Typically, construction of the deck begins with the layout, digging, and pouring of the concrete piers or footings that will support the deck. Smaller decks can often utilize precast pier blocks, while larger decks may require piers that are sunk into the ground to a depth below the frost line. Galvanized steel brackets imbedded in the concrete provide a convenient and stable attachment point for the transition from the concrete to the faming lumber.
If the deck is attached to the house, the next step is installation of the ledger. The ledger provides an attachment to the house, and serves as the starting point for the deck framing. A ledger is typically made of the same size and type of material as the deck framing, and it’s important that it be securely bolted to the house’s structural framing.
It’s also important that the ledger be level and at the correct height, depending on where the finished deck will be in relation to the house. For example, if you will be stepping out a door and directly onto the deck, the ledger should be located at a distance below the door that is equal to the thickness of the decking material you’ll be using.
Using the ledger as a reference point, the rest of the framing takes off from there. Using string lines, a laser level or other means to establish their location in relation to the ledger, the support girders are installed next. The girders are supported by posts attached to the piers, and are installed perpendicular to the direction of the joists.
The final underframing step is the installation of the joists. These are installed perpendicular to the direction that the decking boards will run, and rest on top of the girders. They are also attached to the ledger at one end. Since the decking is typically installed parallel to the house, that means that the joists would be perpendicular to the house, intersecting the ledger at a 90-degree angle. Galvanized steel joist hangers are the most common method for attachment and support of the ends of the joists where they meet the ledger. Depending on the size of the deck, blocking and/or bracing may be required as well.
If your deck is freestanding and is not attached to the house, the overall construction process is pretty much the same. However, since a freestanding deck lacks the rigidity of the house to anchor one side, it often requires some additional bracing to stabilize the framing.
With the basic framing complete, you can now move on to the installation of the deck boards, which are laid perpendicular to the joists. The most common attachment method is to screw down through the board into the joist below — don’t use nails, which have more of a tendency to work loose as the framing dries out. If you would prefer not to see the screw heads, there are several different methods of concealed fastener installation — check with your designer or a local lumberyard for options that will work best for your particular deck design.
For the best appearance, use the longest boards possible so that you can eliminate some of the end-to-end joints. For example, on a 16-foot deck it’s preferable to use 16-foot boards instead of two 8-foot boards. If the deck is large enough that joints are required, stagger them between successive rows by a minimum of two joists. For example, a 24-foot deck might start with a row of two 12-foot boards, followed by a row made up of three 8-foot boards. This will look better and be a little more stable than a row with one 10-foot and one 14-foot board.
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