rmayo
January 16, 2016, 4:44am
21
Bradley,
I switched the pdf files for pictures.
frotte
January 16, 2016, 5:19pm
22
kshepard:
Traditionally-framed cathedral ceilings sometimes use rafter ties on extended centers with more heavily reinforced framing to accommodate the increased lateral loads.
Things sort of turn into a mess every time you start dealing with terms. The “Rafter Ties” are whatever struts connect the bottoms of opposing rafter pairs together to keep the bottoms of the rafter pairs from spreading due to the weight of the roof.
Collar ties go in the upper 1/3 of the roof and are designed to prevent damage form wind uplift.
In a typical home, rafters are resting on tops of walls and the ceiling joists keep the walls from spreading. In an A-frame, the rafters connect with the floor assembly instead of the tops of the walls, so instead of the ceiling joists, the floor joists serve as the rafter ties.
Whatever you call the struts that connect the bottoms of opposing rafter pairs, they need to terminate in the lower 1/3 of the height of the roof, measured from the point of bearing of the rafter heel (whatever the rafter rests on at the lower end) to the bottom of the plumb cut at the ridge. Some people might argue that it’s the top of the ridge, but I’ve never seen any specific dimension, only the lower third of the roof called out as correct.
A bird’s mouth has almost nothing to do with the need for struts connecting opposing rafter pairs, and the forces that try to spread rafter bottoms apart. Bird’s mouths are just notches in rafter bottoms that provide better bearing and nailing characteristics.
The laws of physics don’t change, and if you’ve got a bunch of homes that appear to defy the laws of physics, they obviously don’t, so you might try to get your hands on a set of plans. I’d like to know how they’re built. No! Don’t call them out as defective. Please investigate and post.
You’re repeating yourself.
jkeresztury
January 18, 2016, 12:22am
23
Doesn’t he always ? He did delete 3 or 4 repeats !
irobertson
January 29, 2016, 10:23pm
24
Thanks Joe. It looks like it still has a self supporting ridge and metal connectors though?
irobertson
January 29, 2016, 10:31pm
25
kshepard:
Traditionally-framed cathedral ceilings sometimes use rafter ties on extended centers with more heavily reinforced framing to accommodate the increased lateral loads.
Things sort of turn into a mess every time you start dealing with terms. The “Rafter Ties” are whatever struts connect the bottoms of opposing rafter pairs together to keep the bottoms of the rafter pairs from spreading due to the weight of the roof.
Collar ties go in the upper 1/3 of the roof and are designed to prevent damage form wind uplift.
In a typical home, rafters are resting on tops of walls and the ceiling joists keep the walls from spreading. In an A-frame, the rafters connect with the floor assembly instead of the tops of the walls, so instead of the ceiling joists, the floor joists serve as the rafter ties.
Whatever you call the struts that connect the bottoms of opposing rafter pairs, they need to terminate in the lower 1/3 of the height of the roof, measured from the point of bearing of the rafter heel (whatever the rafter rests on at the lower end) to the bottom of the plumb cut at the ridge. Some people might argue that it’s the top of the ridge, but I’ve never seen any specific dimension, only the lower third of the roof called out as correct.
A bird’s mouth has almost nothing to do with the need for struts connecting opposing rafter pairs, and the forces that try to spread rafter bottoms apart. Bird’s mouths are just notches in rafter bottoms that provide better bearing and nailing characteristics.
The laws of physics don’t change, and if you’ve got a bunch of homes that appear to defy the laws of physics, they obviously don’t, so you might try to get your hands on a set of plans. I’d like to know how they’re built. No! Don’t call them out as defective. Please investigate and post.
So this is what I found out. I talked to the BA and apparently (this is coming from him) the client got the town’s information on it and they apparently passed it. Then he got an engineer in there who apparently said it was fine, but may do better with rafter ties but said they were not necessary. Then he got a home builder in there who said they were not necessary, but the client insisted they were so he gave him a quote for doing it although he said he thinks he doesn’t need them.
So in short, what the code enforcer I talked to said seems to be true: If there is no self supporting ridge you can still have enough structural strength for the ceiling and the collar ties can sort of act as a rafter tie AND the collar ties in certain situations like that. I just looked up a bunch of stuff on it and it all seems to add up.