Thanks, Francis.
The span tables in the IRC are not for wet use. That said, the only result of slightly overspanning is too much deflection. The tables are based on L/360 deflection, which is pretty minimal considering decks don't have any brittle finish beneath them like a plaster or gypsum ceiling below, nor do they typically carry the amount of furniture that causes the serviceability issues from a rocking grandfather clock when the kids run across the room. There was some serious discussion as to if that deflection limit is even an appropriate deflection for decks, and during testimony when it was proposed to specifically add "decks" to the load table next to "floors", there was enough doubt as to what it should be that it was not added. That said, all the new tables in the 2015 are based on L/360. Let's just remember that overspanning does not cause structural collapse. Deflection is the controlling limit when it comes to span.
The 2015 IRC has joist and beam span tables specifically for decks and deck environmental conditions. It also has limits for various post cross sections. I put a lot of work into new deck provisions for the 2015 IRC, but so did many others along my side. The AWC, NAHB, NADRA, CLMA, SST, OMG, and representatives from about six different ICC chapters (and sorry for those others that didn't come to mind right now). It was teamwork and collaboration at it's finest. I hope you think it produced quality code. It sure wasn't easy, but it's how code should be developed.
The span tables in the IRC are not for wet use. That said, the only result of slightly overspanning is too much deflection. The tables are based on L/360 deflection, which is pretty minimal considering decks don't have any brittle finish beneath them like a plaster or gypsum ceiling below, nor do they typically carry the amount of furniture that causes the serviceability issues from a rocking grandfather clock when the kids run across the room. There was some serious discussion as to if that deflection limit is even an appropriate deflection for decks, and during testimony when it was proposed to specifically add "decks" to the load table next to "floors", there was enough doubt as to what it should be that it was not added. That said, all the new tables in the 2015 are based on L/360. Let's just remember that overspanning does not cause structural collapse. Deflection is the controlling limit when it comes to span.
The 2015 IRC has joist and beam span tables specifically for decks and deck environmental conditions. It also has limits for various post cross sections. I put a lot of work into new deck provisions for the 2015 IRC, but so did many others along my side. The AWC, NAHB, NADRA, CLMA, SST, OMG, and representatives from about six different ICC chapters (and sorry for those others that didn't come to mind right now). It was teamwork and collaboration at it's finest. I hope you think it produced quality code. It sure wasn't easy, but it's how code should be developed.