How to Plan Deck Framing & Support

Foundation

• 1

  Stake out the area first with string and stakes pounded into the ground to get a good idea of the size you want to build your deck. Take into consideration the span of the deck. If you build a deck that requires longer spans, the deck will need additional support underneath the deck joists.

• 2

  Pick a foundation type for your support posts. While deck posts can be built on pre-made concrete piers, for a secure deck, it’s best to build concrete footings to support the deck posts. Determine the number of supports after determining deck and lumber sizes.

• 3

  Check with the local building department to ensure your foundation plans meet the code requirements for your deck foundation.

Framing Lumber and Supports

• 4

  Make a decision to build a freestanding deck or one attached to the house. For one attached to the house, check if your house has the capability to accept an exterior ledger. Broken ledgers are one of the leading causes of deck failures because the do-it-yourself builder doesn’t attach the ledger properly to the house. The ledger is part of the external support of the deck and must be bolted to the house with through bolts, such as carriage bolts or massive lag screws to prevent it pulling away from the house.

• 5

  Settle on the lumber type for the support structure and framing. While redwood is a good wood for the deck surface, it is a soft wood and isn’t that good at supporting the deck. Douglas fir is a good choice for deck posts and joists, either as 4-by-4 inch support posts or larger and 2-by-8-inch to 2-by-12-inch ledgers and joists. Then pick a deck surface, such as redwood or a hardwood that weathers well such as teak, taking cost into consideration (teak, for example, is expensive).

• 6

  Calculate the joist span and determine the spacing between the joists. This is critical when building the frame for the deck. The rim joists, ledgers and supporting joists are graded based upon their maximum spans and support capabilities. Larger support boards also contribute to the weight of the deck and this needs to be figured in when choosing the support posts. Don’t undersize the wood for the framing if you want a deck that lasts and has structural integrity. The spacing between joists also adds to the distance the joist can span. Standard deck building practices call for joists 16 or 24 inches center to center, or "on center."

• 7

  Pick quality lumber. Sight boards along their edges down the length to choose only the boards that are straight and not crowned. Boards that have a slight warp to them don't provide the right support and usually warp even more once in place. To sight a board, hold one end up to your eye and sight along its length while it is on its shortest side. Turn the board over and sight again along its widest side. This allows you to note any board imperfections, twisting and warping. Choose only straight lumber for your deck. Kiln dried is best, as it is already dried wood.

Hardware

• 8

  Pick the hardware for the application. For instance, if attaching a ledger to your house when building an attached deck, purchase carriage bolts and ensure you have access to secure them with a nut on the inside area of the house through its rim joist. The other alternative is using heavy-duty lag screws, but check with local building codes to confirm these will work.

• 9

  Select joist hangers and post brackets needed for the type of deck you will build.
  Small deck screws won’t cut it for securing the ledger to the house. Decide to build a freestanding deck or an attached deck, as this is critical to making a list of the right hardware and lumber needed.

• 10

  Use the right wood screws for securing the deck boards to the frame. Most deck boards are 2-by-6 boards and require deck screws capable of going through the deck board and fastening securely to the support joist below. Don’t use nails, as hot and cold expansion during weather changes will cause these to pull out. Standard deck screws are typically 3 inches or longer.