A friend of mine recently bought a house that has a stick framed hip roof over his deck, which is about 14'x20'. The roof does not look to be original to the house and obviously not designed/constructed to code, considering it is sagging significantly. It was probably constructed about 10-15 years ago. Given that I deal primarily with bridges, I do not have the expertise to fully redesign his roof for him, but I would like to let him know what to expect when he hires a engineer/contractor.
A quick description... The hip starts immediately at the connection to the house, which is a vertical wall, 2 storeys high. In other words, there is no ridge beam typical of rafter-framed construction. Similarly, there are no collar ties so the ceiling vaults increasingly as you get closer to the house. If you can imagine, the peak of the hip sits a few feet above the second storey floor. They simply connected the two "hip beams" to a board nailed to the side of the wall. I highly doubt they reinforced the stud wall by adding a built-up column inside. The other three sides of the roof are supported by a 4x8 beam with 4x4 posts at ~4' o.c. and 2x4 cross-bracing beneath the hand rail. I hope this gives the idea of what we're looking at...
My friend (actually his wife) likes the look/feel of the roof so they'd like to replace it as is. My primary concerns are as follows:
1) Hip beams are undersized (I checked). Easy enough to fix during reconstruction though.
2) The vertical reactions of the hip beams are being supported by the exterior stud wall of the house. I feel they need to add a column to the exterior face to take this concentrated load.
3) I'm assuming the lateral thrust is being absorbed through the second floor diaphragm of the house, as well as the cross-bracing of the deck rail. I'm concerned that this isn't good practice and the structure should be laterally self-supporting.
My questions are as follows:
1) Are wood diaphragms effective over the ridges of the hip? I'd assume they would be but just figured I'd ask.
2) Is it common to absorb rafter thrust through diaphragm action to exterior walls, rather than more common methods such as ceiling joists or collar ties?
3) Am I correct in assuming that stud walls should not take concentrated loads of this magnitude?
4) Am I overlooking anything?
Thanks!
A quick description... The hip starts immediately at the connection to the house, which is a vertical wall, 2 storeys high. In other words, there is no ridge beam typical of rafter-framed construction. Similarly, there are no collar ties so the ceiling vaults increasingly as you get closer to the house. If you can imagine, the peak of the hip sits a few feet above the second storey floor. They simply connected the two "hip beams" to a board nailed to the side of the wall. I highly doubt they reinforced the stud wall by adding a built-up column inside. The other three sides of the roof are supported by a 4x8 beam with 4x4 posts at ~4' o.c. and 2x4 cross-bracing beneath the hand rail. I hope this gives the idea of what we're looking at...
My friend (actually his wife) likes the look/feel of the roof so they'd like to replace it as is. My primary concerns are as follows:
1) Hip beams are undersized (I checked). Easy enough to fix during reconstruction though.
2) The vertical reactions of the hip beams are being supported by the exterior stud wall of the house. I feel they need to add a column to the exterior face to take this concentrated load.
3) I'm assuming the lateral thrust is being absorbed through the second floor diaphragm of the house, as well as the cross-bracing of the deck rail. I'm concerned that this isn't good practice and the structure should be laterally self-supporting.
My questions are as follows:
1) Are wood diaphragms effective over the ridges of the hip? I'd assume they would be but just figured I'd ask.
2) Is it common to absorb rafter thrust through diaphragm action to exterior walls, rather than more common methods such as ceiling joists or collar ties?
3) Am I correct in assuming that stud walls should not take concentrated loads of this magnitude?
4) Am I overlooking anything?
Thanks!
