The laws of physics do not change when you go from 48" to 49". You find this restriction in Appendix Chapter A3, which was superseded Standard Plan A because engineer Jim Russel, the chair of the Appendix Chapter A3 committee, found Appendix Chapter A3 so lacking that he believed it should be replaced. Both Appendix Chapter A3 and Standard Plan A have this 4' height restriction. Both standards state that if the cripple wall is over 4' one must hire an engineer. There are links to these two standards
on this webpage. The only difference between a retrofit with cripple walls over 4 feet is that you will probably want to put in hold downs in some locations
to resist overturning. Where these should go is simple common sense.
I was on the Standard Plan A committee and its authors well, all of whom were engineers. So far as I can tell this 4' was specified so engineers could get all the easy retrofits where you can stand up, while contractors were given the ones where you had to crawl on their bellies and rub their faces into the dirt. In other words, keep the easy ones for yourself and the crap to contractors. That is the only explanation I can come up with anyhow.
I have no idea if I read this correctly, but that is what I believe about the 4' restriction.
Here is another way of putting it
First you need to understand why Standard Plan A has this recommendation. This has to do with aspect ratios which is the ratio of a shear's height to its length. For example a shear wall with a 2:1 ratio would be twice as fall as it is wide.
When lateral forces are applied to the top of a shear wall that is taller than it is wide, the shear wall will want to flip over or overturn which will pull out all the nails at the bottom the shear wall. This video explains it all. Standard Plan A does not want any shear walls to be taller than they are wide because of the potential for overturning. If there is overturning potential they want you to have an engineer figure out what to do about it. Engineers recommend the same solution 100% of the time. Simply install one Simpson one HDU2 on each end of the shear wall as explained in this video.
Personally, I don't think overturning is a big deal based on these tests.
These videos on more can be seen on this webpage.
Please subscribe to my YouTube channel.
The laws of physics do not change when you go from 48" to 49". You find this restriction in Appendix Chapter A3, which was superseded Standard Plan A because engineer Jim Russel, the chair of the Appendix Chapter A3 committee, found Appendix Chapter A3 so lacking that he believed it should be replaced. Both Appendix Chapter A3 and Standard Plan A have this 4' height restriction. Both standards state that if the cripple wall is over 4' one must hire an engineer. There are links to these two standards
on this webpage. The only difference between a retrofit with cripple walls over 4 feet is that you will probably want to put in hold downs in some locations
to resist overturning. Where these should go is simple common sense.
I was on the Standard Plan A committee and its authors well, all of whom were engineers. So far as I can tell this 4' was specified so engineers could get all the easy retrofits where you can stand up, while contractors were given the ones where you had to crawl on their bellies and rub their faces into the dirt. In other words, keep the easy ones for yourself and the crap to contractors. That is the only explanation I can come up with anyhow.
I have no idea if I read this correctly, but that is what I believe about the 4' restriction.
Here is another way of putting it
First you need to understand why Standard Plan A has this recommendation. This has to do with aspect ratios which is the ratio of a shear's height to its length. For example a shear wall with a 2:1 ratio would be twice as fall as it is wide.
When lateral forces are applied to the top of a shear wall that is taller than it is wide, the shear wall will want to flip over or overturn which will pull out all the nails at the bottom the shear wall. This video explains it all. Standard Plan A does not want any shear walls to be taller than they are wide because of the potential for overturning. If there is overturning potential they want you to have an engineer figure out what to do about it. Engineers recommend the same solution 100% of the time. Simply install one Simpson one HDU2 on each end of the shear wall as explained in this video.
Personally, I don't think overturning is a big deal based on these tests.
These videos on more can be seen on this webpage.
Please subscribe to my YouTube channel.
