Two Story Cantilever

[bnymbill]

I'd like to know what the codes are for building a 3 story house with the 2nd and 3rd floor cantilevered. There are two ways to do this:

1. If the 2nd floor is cantilevered 3' past the 1st floor, can the 3rd floor be cantilevered 3' past the 2nd floor? Both are assuming joists extend 9' back into structure.

2. If the 2nd floor is cantilevered 3' past the 1st floor, can the 3rd floor be built on the same footprint as the 2nd floor?

Does the weight and leverage of an additional story of house reduce the distance of cantilever the 2nd story can extend?

Thank you,

John

 

[ICE]

That sounds like a fun project for an engineer.

 

[Francis Vineyard]

Sure does ICE . . . by the way welcome to the forum John

R502.3.3 Floor cantilevers.

Floor cantilever spans shall not exceed the nominal depth of the wood floor joist. Floor cantilevers constructed in accordance with Table R502.3.3(1) shall be permitted when supporting a light-frame bearing wall and roof only. Floor cantilevers supporting an exterior balcony are permitted to be constructed in accordance with Table R502.3.3(2)

Francis

 

[GBrackins]

Welcome to the Forum!

Francis gave your the prescriptive code requirement. Since what you propose is not compliant with the code you'd need to hire a professional engineer to design it for you.

 

[Frank]

With proper engineering all of the above and more can be done, at some cost that the owner may or may not want to pay. Even to the point of hanging the third floor from properly designed roof trusses that bear on an interior beam and column system with the opposite wall acting in tension.

If the architect can lay it out, the engineer can make it stay up, the only question is cost.

Definately in PE Design range.

 

[DRP]

Brings to mind the old jettied timberframes overhanging the streets in places in europe. In some cases the back walls have more column or even masonry where they are out on heavily loaded overhanging beams in front. as they have deflected and crept over the years not only do the buildings step out over the sidewalk, they lean out over it more. Luckily the streets are narrow.

 

[Daddy-0-]

I agree with all of the posts above requiring engineering so the only other thing to say is welcome. Do you a plan or picture you can post?

 

[bnymbill]

Hey guys - thanks for the responses. Sorry it took so long to respond - I was expecting email notifications when I had responses to view. I'll update if/when I reach a conclusion on this project.