• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Rafter Thrust

jar546

jar546

Forum Coordinator
Joined
Oct 16, 2009
Messages
11,051
Location
Somewhere Too Hot & Humid
Thoughts on rafter thrust with this beam put in place? What is taking the place of overlap? FYI this house has a ridge board, not a ridge beam.

IMAG0104.jpg
 
That looks like any of a hundred frame jobs I have seen...and failed back in the day. Lots of engineering solutions have been come up with after the fact, many some variation of the strap steveray shows. I encountered this very heavily in the rural south, and saw more than a few failures where the exterior walls were blowing out. Very common in "bonus room" framing which is usually made worse by using knee walls at the exterior. Once demonstrated the issue to a builder (on a very nice home) by having him help me measure across the room at the bottom and the top plate. I asked him if he purposely installed the knee walls several inches out of plumb. This was made very apparent by the "temporary" t-posts they were using to hold up the ridge board. It was bowed so badly the nails were bending at the connection.

In Jar's photo a flat strap across the bottom would do it, but might ruin the finish product. Also, I rarely have seen ledger framing outside of the south, which makes a nice finish, but the ledger nails look a little far apart.
 
I don’t see the problem. Looks like 3 toe nails from the joist, part way into the beam web … we always do it that way …
 
So this is what they are trying to rercreate:

1692625904666.png

3-16d is about 360# in shear if I remember....So lets call it 400# these are not giant forces we are dealing with....The flat strap under is a problem for the drywaller ...
 
Sorry...mis-clip.....at 30# load and a 7 pitch or steeper, it's about the same (what's a 16d or 2 amongst friends..Not that anyone builds with 16ds anyway, so it probably has 10 10ds....And kind of moot as once again...It's all trusses per the energy code around here now...

1692630446221.png
 

Attachments

  • 1692630429179.png
    1692630429179.png
    7.4 KB · Views: 0
steveray said:
I recommend a Simpson VB-7...but it is way overkill, but you can point to it in the book, so it is easy.......You are looking at controlling about 400# if you are using the prescriptive nail connection...

View attachment 11170
Click to expand...
www.strongtie.com

VB

The VB provides lateral resistance force at the bottom of beams when installed approximately 45° or more to the vertical plane.
www.strongtie.com www.strongtie.com

Screenshot 2023-08-21 at 10-23-08 C_VB10_2DP_Cad_ISO_Instld.dwg - C_VB10_2DP_Cad_ISO_Instld.pdf.png
Never seen this used. Usually see CS-22. Almost always specified by an engineer. The dry-waller can work around it.
 
e hilton said:
I don’t see the problem. Looks like 3 toe nails from the joist, part way into the beam web … we always do it that way …
Click to expand...
Referring to the ledger nails. I had it in my head that they should be closer, but the current codes don't give a dimension, and the code I thought they exceeded calls it 4" o/c, so these are probably fine. Ledger framing provides a much better finish, produces less squeaks, and is cheaper and quicker. JMHO.
 
Jar, are there any collar or rafter ties above the CJ/Beam connections to prevent spread?
 
Sifu said:
Referring to the ledger nails. I had it in my head that they should be closer, but the current codes don't give a dimension, and the code I thought they exceeded calls it 4" o/c, so these are probably fine. Ledger framing provides a much better finish, produces less squeaks, and is cheaper and quicker. JMHO.
Click to expand...
You mean this?

1692650201938.png
 
steveray said:
You mean this?

View attachment 11183
Click to expand...
Yes. Back in the day in another state with a state code, they prescribed it in this table and I guess I mis-remembered it as "within 3" of the joist, so one nail under and 2 or 3 within 3" of the joist. But, I went back and can only find that it says 4" o/c. It may have come from an earlier edition, or it may be that I have been wrong all along, and current code has no distance prescription anyway with "At each joist".
 
You must log in or register to reply here.
Top