Lake06
Civil/Environmental
- Feb 22, 2011
- 45
I am involved with a repair for a newly constructed home. The home has a valuated ceiling area and it was determined that a ridge board was utilized with collar ties located in the upper 3rd height. I realize that this should have been constructed with a ridge beam and not a ridge board. The home has all its finishes completed.
Owner would not like to utilize a ridge beam for the repair because this would involve ripping up the top of the ceiling and the height would make it difficult to install. I am thinking of utilizing 3 lvl boards (14”x1.75”) laid on their side and 2 lvl (9”x1.75”) running vertical to form an inverted T shape. This beam would run parallel to the top double plate of the house were the rafter meets the exterior wall. (I will post a picture of this detail later). I would install 2x12 joists which would tie the rafter into this lvl beam at 24” o.c. The double top plate and proposed beam would run parallel but would be aprox 1.5’ apart. There would be a proposed beam on each side of the home.
The home has a 12 on 12 roof slope with 2x12 rafters at 24” o.c. The valuated ceiling area is 28 feet wide by 20 feet long with the ridge running in the 20 foot dimension. The rafter is currently nailed into the double top plate with 5, 8d common nails and has a hurricane strap with provides 160 lbs of lateral resistance. I have calculated the lateral thrust due to dead load to be 210lbs per rafter. The lateral thrust due to dead and snow load was calculated to be 760 lbs per rafter. The exterior walls are 2x6 construction with ½” osb sheeting.
I have seen this detailed before to utilize this lvl beam but not sure of how to connect the beam at the ends. The lateral reaction would be very high at the ends of the beam. I was thinking of utilizing a 3/8” dia cable. This cable would be located at the ends of the beam and tie the beam into the opposite proposed beam located on the other side of the room. The cable can be hidden in the wall. Does anyone have any thoughts or comments on this? I guess the alternative would be installing rafter ties spanning the room located 4 feet above the top exterior plate spaced at 4 feet on center with ties nailed or bolted to both sides of the rafter.
Owner would not like to utilize a ridge beam for the repair because this would involve ripping up the top of the ceiling and the height would make it difficult to install. I am thinking of utilizing 3 lvl boards (14”x1.75”) laid on their side and 2 lvl (9”x1.75”) running vertical to form an inverted T shape. This beam would run parallel to the top double plate of the house were the rafter meets the exterior wall. (I will post a picture of this detail later). I would install 2x12 joists which would tie the rafter into this lvl beam at 24” o.c. The double top plate and proposed beam would run parallel but would be aprox 1.5’ apart. There would be a proposed beam on each side of the home.
The home has a 12 on 12 roof slope with 2x12 rafters at 24” o.c. The valuated ceiling area is 28 feet wide by 20 feet long with the ridge running in the 20 foot dimension. The rafter is currently nailed into the double top plate with 5, 8d common nails and has a hurricane strap with provides 160 lbs of lateral resistance. I have calculated the lateral thrust due to dead load to be 210lbs per rafter. The lateral thrust due to dead and snow load was calculated to be 760 lbs per rafter. The exterior walls are 2x6 construction with ½” osb sheeting.
I have seen this detailed before to utilize this lvl beam but not sure of how to connect the beam at the ends. The lateral reaction would be very high at the ends of the beam. I was thinking of utilizing a 3/8” dia cable. This cable would be located at the ends of the beam and tie the beam into the opposite proposed beam located on the other side of the room. The cable can be hidden in the wall. Does anyone have any thoughts or comments on this? I guess the alternative would be installing rafter ties spanning the room located 4 feet above the top exterior plate spaced at 4 feet on center with ties nailed or bolted to both sides of the rafter.
