Cantilevered Decks and Balconies
Cantilevered Decks and Balconies
(OP)
When you compare Table 2 from the DCA6 to a similar Table (R502.3.3(2))in the 2012 IRC for cantilever spans for floor joists supporting exterior balconies there is a huge discrepancy.
For a 2x10 floor joist @ 24" o/c spacing I can construct a cantilevered balcony per the IRC with cantilever span of 43" and a backspan with a 2:1 ratio.
Using the same 2x10 deck joist @ 24" o/c spacing I can only create a cantilever of 2'-9" and the backspan must be a 4:1 ratio per the AWC DCA6 document.
Why is the AWC DCA6 so conservative? I must be missing something here. I've attached a quick calculation for this scenario and with a 220 lbs point load I'm well below capacity of the joist in bending or any other parameters.
For a 2x10 floor joist @ 24" o/c spacing I can construct a cantilevered balcony per the IRC with cantilever span of 43" and a backspan with a 2:1 ratio.
Using the same 2x10 deck joist @ 24" o/c spacing I can only create a cantilever of 2'-9" and the backspan must be a 4:1 ratio per the AWC DCA6 document.
Why is the AWC DCA6 so conservative? I must be missing something here. I've attached a quick calculation for this scenario and with a 220 lbs point load I'm well below capacity of the joist in bending or any other parameters.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com






RE: Cantilevered Decks and Balconies
Mike McCann, PE, SE (WA)
RE: Cantilevered Decks and Balconies
Also, could it be the incising factor based on the AWC assuming treated wood?
You using same Cd factors? Tables may be assuming different values. I don't have AWC DCA6, just brainstorming.
RE: Cantilevered Decks and Balconies
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com