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A deck beam is a supportive post that holds the weight of decking materials and any persons or items placed on the deck. These are typically bolted to the established deck beam posts. When attaching deck beams to posts, it is important to provide support for lumber above and beyond nails and bolts, which may weaken over time and fail to properly support the structure.
Most often, deck beams are created from lumber that measures two inches (5.08 cm) by 12 inches (30.48 cm). The wood will be cut down to the proper length based upon the deck plan. Each deck beam will need to be secured to a deck post using either a deck beam joist or a notch-and-bolt technique.
The deck beam joist is a metal bracket that is bolted to a footer post and a deck beam. Joists support the weight of the beams, floor boards, and handrails attached to the deck. One footer is required at all four corners of the deck, and at measured spaces on the underside of the deck for additional support. The number and spacing between footers and beams will be determined by the overall weight of the deck. This weight can add up to several tons, once furniture is placed on deck floors and people begin to use the space.
Deck joists are also used to attach deck beams to the structure of the home. These joists need to be bolted into a solid stud through a home's exterior. Footer posts can also be used to support the weight of deck beams, if studs are not strong enough to support the deck.
A notch-and-bolt technique can be used in place of deck beam joists to support the beams. This technique uses oversized footer posts. Posts are notched with a circulating saw to hold the width of deck beams. The deck beam is then attached to the footer using carriage bolts.
Notches can be cut out of two sides to support corner deck beams. The remaining posts are often notched in the middle to support the single beam that runs the depth, or width, of the entire deck. Deck beams can be placed either parallel or perpendicular to the home, depending on the approved deck plans.
Properly supported beams are required by many local and state building laws and codes. Before building a deck, local building agencies may need to approve the deck plan. After the structure is complete, an inspection may be needed in order to pass local and state construction codes.