Where posts and beam or girder construction is used to support floor framing, positive connections shall be provided to ensure against uplift and lateral displacement. IRC R502.7 & IBC 2308.8.2 Joists must be supported laterally at the ends by solid blocking or attachment to a full depth header, band or rim joist (IRC & IBC).
The bigger you make your deck, the more you ask of the framing timbers that hold up the deck's structure, and the joists and beams that support the deck's floor can only span so far before the ...
The 2015 IRC includes a new table R507.6 Deck Beam Spans Lengths. The table makes it easier for deck builders to accurately size deck beams and for inspectors to check decks for adequate framing. Sizing deck beams got a lot easier when the 2015 IRC came out.
If a joist spans between two beams or a beam and a ledger, each beam (or ledger) supports half of the joist. The length of joist span actually supported by a beam is what determines the force that bears upon that beam and therefore the distance that a given size of beam can span before another post is required to support that beam.
The tributary area supported by a post equals half the beam length on each side of the post multiplied by half the joist length to the next support, such as another beam or the ledger.
Low decks might not provide enough vertical space for joists attached to the top of a beam. The solution is a flush beam, which is essentially a header that has been doubled for strength. Cut two headers (the boards that will be perpendicular to the joists) and mark lines on them indicating where the joists will go.
Installing 2x8 Deck Beams If the outside edge of your deck is at least 17” above grade, a double 2x8 beam should be installed to support the joists along the outside. The joists will then extend over the beam in a cantilever position.
Beam should be MIN 2 2x12's with 4x6 or 6x6 posts every 8' and if it is a taller deck add 1 more support post. 2' Cantilever over the beam would be just fine and if you did do 2' then 16" O.C. joists would be fine (since the joists are now only spanning 10')
Sample Calculations for Using Joist Span and Beam Size ... With a 12’ deck span, the beam may be either two 2x8s or two 2x10s, depending on wood used. CASE II SOLUTION: ... 2. When joist extends (cantilevers) beyond support beam by 18” or more, add 1” to footing dimensions shown.
For deck joists perpendicular to house wall, a much-preferred alternate method of support is to install a beam (girder) about 2 to 3 feet away from (and parallel to) the house wall. Although this method will cost more than connecting ledger board to house, the support provided is much more secure.
Deck Building Beam Options. The Deck Building Beam sits on the footings, it carries the joists and gives the main support to the surface decking. Depending on which type of deck you want to build - there are different structural options to take into consideration.
Most Decks Can Be "Free Standing" or "Floating" Did you know this? If your deck is 6 feet or less with proper post to beam and joist bracing, it is a perfect candidate for a floating deck.
A beam is a solid structural member that is supported by posts and footings that accepts and transfers the load from joists. Once you know the distance between support posts and the length of the joists that will be supported you can determine the required size by checking our beam-sizing chart.
How to build & install a built-up structural beam for decks, porches, & simliar structures. This article describes how to build a beam used to support a deck or porch floor or similar structure. We describe building the beam out of 2x lumber in four easy-to-follow steps.