Ridge Board or Ridge Beam for Hips?
Ridge Board or Ridge Beam for Hips?
(OP)
Ok, really been scratching my head on this one but probably looking way too much into it...
I have a 4/12 hip roof I am designing for a friend, the width on the addition is 34' and the length is about 22 feet, The roof will tie into the existing with a sleeper. I tried convincing him on pre-engineered trusses but he didn't want them. I am using 2x10 roof rafters (24" o.c.) and 2x8 collar ties/ceiling joists, with a bearing wall (near mid span) running the full length perpendicular to the width. I understand the ridge can be designed as a "ridge board" because the ceiling joists will resist the outward thrust and the collar ties will resist wind. However, for some reason I am having a hard time picturing the same case for the hip ridges. To throw a wrench in the whole thing I have a vaulted ceiling under a portion of one of the hip ridges.I believe I have the right design but maybe someone could chime in and help me have a clearer picture of this...
I have a 4/12 hip roof I am designing for a friend, the width on the addition is 34' and the length is about 22 feet, The roof will tie into the existing with a sleeper. I tried convincing him on pre-engineered trusses but he didn't want them. I am using 2x10 roof rafters (24" o.c.) and 2x8 collar ties/ceiling joists, with a bearing wall (near mid span) running the full length perpendicular to the width. I understand the ridge can be designed as a "ridge board" because the ceiling joists will resist the outward thrust and the collar ties will resist wind. However, for some reason I am having a hard time picturing the same case for the hip ridges. To throw a wrench in the whole thing I have a vaulted ceiling under a portion of one of the hip ridges.I believe I have the right design but maybe someone could chime in and help me have a clearer picture of this...






RE: Ridge Board or Ridge Beam for Hips?
Anyway, that is my long winded way of saying you must resist the horizontal reaction at the top of the hip beam, and the horizontal and vertical reactions at the bottom of the hip beam.
DaveAtkins
RE: Ridge Board or Ridge Beam for Hips?
There is a vast difference btwn. “2x8 collar ties/ceiling joists” and you must sort this out to determine how these help resolve the forces in your roof system, they are not one in the same. The concept of the ridge board and opposing rafters is a long tested and used means of a roof structure. It is easy to understand an analyze, when done properly. The hip ridge or valley member is less easy to design, analyze and rationalize, so it is not unreasonable that these members be treated a huskier beam members. These are often ripped on the top edges to match the roof planes. If you have a bearing wall under the ridge, it is not uncommon to provide a column under the ridge, where the two hip ridge members meet. This just adds a little extra safety to the roof framing system with little added cost. As mentioned above, the horiz. trust must still be considered down at the double top plate of the walls, it can still push that corner, those walls, out if not detailed for.
RE: Ridge Board or Ridge Beam for Hips?
RE: Ridge Board or Ridge Beam for Hips?
RE: Ridge Board or Ridge Beam for Hips?
DaveAtkins