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cantivered 2nd story

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rittz

Structural
Dec 30, 2007
200
My client wants to cantilever the second story 2 to 4ft over the
first story at the front and back. I propose supporting it on cantilevered
WF beams at 10 or 12’ oc. spanning from the center beam to the o/s walls. The beams support no load other than the roof and wall load of the 2nd story.
The floor joist do not cantilever but span from o/s walls to the center beam.
I wonder how to calculate the upward deflection of the cantilevered Wf’s at mid span and even it is significant.
see also attached sketch
 
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Normally, the cantilever is picked up by cantilevering the floor joists. Your framing method with the extra steel beams under the floor joists seems somewhat redundant to me, except for the central steel beam..

Mike McCann
MMC Engineering
 
Another thought here, unless you do cantilever the floor joists, you will read a break in the floor system at the first floor outside wall line of the second floor. The cantilever will eliminate this situation if properly designed. Continuity is good!

Is there a reason why the floor joists are not cantilevered?

Mike McCann
MMC Engineering
 

Thanks Mike
The exterior walls are ICF blocks (6" of comcrete sandwiched between 2 pieces of 2" styrofoam) (incidently I hate them) I was concerned about supporting a concrete wall like that on plain 2x10 joists. and the posible problem with differential shrinkage. Now I'm thinking of cantilevering 16"deep open web pre-engineered wood truss joists and thinking that would work satisfactorily.
The onerhang varies from 2' in places to a max 4' in a short wall.
 
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