![]() ![]() Recommended or allowable joist & beam spans: this article explains typical spans for deck joists, deck beams, and deck flooring, giving both standard span tables and a quick "rule of thumb" that works pretty well. We have no relationship with advertisers, products, or services discussed at this website.įraming tables for decks: joist & beam spans & sizes. He also advises the North American Deck and Railing Association on code issues and provides free education online at tolerates no conflicts of interest. ![]() Glenn Mathewson is a municipal building inspector and deck construction expert in Colorado. Negotiations and research are already underway for 2018 IRC proposals (due in 2016), and you are welcome to contribute. However, they are still a work in progress. These are just some of the highlights of new provisions coming in the 2015 IRC that tighten the reins on the decking industry, something that’s been a long time coming. Requirements for exterior stairway lighting were revised to be more understandable and clearly require a light at the top landing. While the foundation provisions aren’t complete, they are a great start to the subject. 4×4 and 4×6 posts are permitted up to 8′ in length, and 6圆s up to 14′.įor those seeking relief from the invasive lateral load detail that requires access inside the floor cavity, a second “permitted” detail is included that is installed entirely from the outside of the building.įoundations details are also provided, allowing for various design approaches, such as embedding posts into pier foundations and how deep the embedment must be. Sizing provisions for posts are included, appropriately limiting their length based on their size. Similar to joists, beams are allowed to cantilever beyond the end post by up to 1/4 the adjacent span of the beam. When there is no joist cantilever, the maximum beam spans are very conservative. The table is based on joist span, as that reflects the load the beam carries however, it is also based on the joists cantilevering their maximum allowable distance beyond the beam. ![]() Creating a pre-engineered beam span table is no easy feat, and many design assumptions have to be made. It includes 2-ply and 3-ply beams and heavy timber Douglas fir beams. Most helpful to the industry, a beam span table is now included, and it’s also based on all the proper conditions and design properties. Many builders may find spans reduced from what they are accustomed to however, the maximum allowable cantilever for deck joists is also clearly defined, and the limit of 1/4 the joist backspan is a generous design option. The new table also reflects the design value changes to Southern pine published in 2012. The 2015 code adds a new joist span table that accounts for these conditions and includes new species and sizes, such as redwood and cedar. ![]() The joist span tables that have long been in the IRC are not based on a wet-use environment or for incised, treated lumber, both conditions that reduce the maximum allowable spans. However, a second “permitted” lateral load anchor detail has been included. The still ambiguous lateral load provisions for decks have not been completely put to rest, and the notorious anchor detail remains. The 2009 IRC saw deck ledgers addressed, the 2012 set up a section in the IRC specific for decks, and the 2015 brings joist and beam span tables, as well as post sizing and foundation provisions. Largely based on prescriptive tables from the American Wood Council’s DCA6 document, many of the new code provisions may look familiar. We asked Glenn Mathewson, a municipal building inspector and deck construction expert based in Colorado, to provide an overview of some of the biggest changes: The 2015 edition of the International Residential Code brings the biggest update of deck codes the IRC has ever seen. ![]()
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