hip roof - wood frame construction - typical residence

huangyhg

hip roof - wood frame construction - typical residence
for a hip roof, with hip beam meeting a non-structural ridge with collar ties, is there a need for a post to support the hip / ridge connection point, or will the vertical load go thru the hip beam to the exterior stud walls.
i believe what you are describing would be a king post truss arrangement with the vertical (king post) and collar tie arrangement.  technically, with only small collar ties, the king post would see little load, and so would not be needed.  if, however, the collar ties are more substantial, approaching more like a stiff beam, then the king post would see load, and hence would be needed.  
so, with small collar ties, you probably will not need a king post to support the hip, but will probably need a beefed-up collar tie at the attachment of the hip.
mike mccann
mccann engineering
you cetainly can make it work without the post but it complicates things.
collar ties will add flexure to the roof joists. the hip arrangement  brings more load to select joists than a plain gabled endwall. depending on the system's stiffness, you might need to consider the horizontal thrust on the sidewalls.
the lower the collar ties, the less the kick out of the sidewalls.
mike mccann
mccann engineering
the collar tie roof truss would need to be designed to incorporate the point reactions from the hip beams, probably requiring beefier members than the typical collar tie roof truss.  i usually check the truss with a pin & roller so you don't create a thrust reaction at the supports, the studwall wouldn't be able to resist that reaction anyway.