Vaulted hip roof?

[MartyM]

  I have done a little searching both here and Google and have found some answers but I was hoping the collective could share some of its knowledge.   

I thought of posting this in the Balloon wall height thread but decided that the hip roof may change the forces at work.

I m wondering if I can put a 4/12 pitch vaulted hip roof on a 8ft x 16ft building?  I have been playing with a tiny house plan and was thinking 9ft walls with small lofts on both ends, one as a sleeping loft the other smaller loft for storage.  The building will have 9ft high walls. The loft floors will be about 7ft. leaving around 18 inch walls in the lofts. I plan on metal coller ties and metal ties at rafter to walls.  Can I do this without a cieling/rafter tie running through my dormers?

[jfmann]

Sketch / diagram would be most helpful to fully understand the proposed configuration. A structural ridge beam might resolve the entire issue .......especially considering the relatively small dimensions which results in relatively small design loads that the beam must resist. However, I do not see (right now) how a hip roof is going to be formed on such a small building unless the entire roof is "hip", or essentially a pyramid shape.

In general, collar ties installed higher than 1/2 the ridge height (above low ends of rafters) result in excessive outward thrust force (for collar tie connections to rafters) and excessive bending force in lower part of rafters.........without detailed design. Also, there is tendency for large spreading at low ends of rafters. Of course, for relatively small dimensions, these problems are not all that significant.......especially if there is no snow load to consider or relatively small snow load.