Mansard Roof Framing

jesuscowboy

Just got fired from a job cause GC told me that rebuilding a mansard roof doesnt require support directly under "flat" part of mansard that the hips will support the "flat" section of roof. And that essential a mansard is a hip roof that you just cut the top out of. Any ideas was I wrong in wanting to add supports under the "flat" deck of mansard. He also told me I could just put a corner loadbearing cantilever unsupported for 8 feet because once the hip and jacks tie into the catilever ridge beam the hip will hold the roof up properly.

neolitic

Are you talking about a mansard, or a gambrel roof?
Either one can be framed to be self supporting.
Ever seen a gambrel barn roof from the inside?
What did the print show?
The second part of your post (blue)
lost me completely.
No idea what you mean.

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Snow Man

Were you following the prints?

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jesuscowboy

no prints just told to go do the job; this is an insurance job. and as far as explaining the corner cantilever; basically the GC told me I could build a beam that would be similiar to a corner window header (no support directly at corner) for the front two sides of the "Flat" square of the mansard. It's really a french mansard where the center section is flat.

neolitic

Still can't see the situation.
If I understand, there are cases
when that might work, and
there are cases when I wouldn't do it.
Not enough information to even make
a guess.
Not sure you can find the vindication
you're looking for without drawings
and more facts.
Good luck finding new work.

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Timuhler

I think there is an old FHB article on a mansard roof. Seems that they engineered it so that the flast portion had to posts.

I talked to our engineer at length a couple of weeks ago because the house we framed had a section of the hip roof that was vaulted and the homeowners decided to leave out the walls too and have the whole kitchen, dining and living room open. With one post directly under the king commons. Ended up we had to add a beam in the floor and another post so the hips would bear.

I talked to him about the hips needing a post. It was interesting talking to him. There are basically 4 approaches to our situation.

1) design the walls so that they resist the outward thrust of the roof ie metal or thicker wall with beefy topplates
2) a ridge beam that can cantilever past a post in a wall and support the roofs (big and expensive beam)
3) cable rafter ties to resist thrust
4) Post under the hips

A lot cheaper to post the roof. http://picasaweb.google.com/TimothyU...52422751520578


Long story short, seems to me you'd need posts unless there was something else in the design.