Return to index: [Subject] [Thread] [Date] [Author]

RE: IRC Table R802.5.1(9) Rafter ties

[Subject Prev][Subject Next][Thread Prev][Thread Next]
You are right on your analysis of the loads and your desire to add posts.
The rafter/ceiling connection requirements would however be close to actual
gable roof values close to the middle of any long walls of a hip roof.  

Be careful on walls running parallel to the ceiling joists.  I've seen a
couple pull apart due to inadequate connection between the two systems.  If
there is a large unsupported area below he may also want to put in a
temporary support to the ridge until the ceiling is sheet rocked so it can
then be "tensioned".  

I would say it's one of the areas where the code is the minimum in all cases
without reduction (erring on the conservative side to hopefully cover all
cases - prescriptively) unless he wants to pay you to analyze the nailing
requirements in a hip roof in order to save (probably not) on a few nails.
;)

Chris
 
Haffner Consulting Engineering
www.haffnerconsulting.com
Office & Fax:  541-478-3052
 

-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com] 
Sent: Wednesday, May 25, 2005 6:38 AM
To: seaint(--nospam--at)seaint.org
Subject: IRC Table R802.5.1(9) Rafter ties

A contractor has asked to tie a rectangular hip roof
in both directions to eliminate interior columns.  IRC
R802.3.1 Ceiling joist and rafter connections states
that Table R802.5.1(9) shall be used to determine the
required number of nails.  That's fine, but is there a
modification factor for hip roofs?  Ties under the hip
rafter areas take considerably less thrust the closer
you get to the parallel walls.  Loads in the longer of
the two directions should also be less than the
shorter direction where the ties are crossing under
the main ridge and carrying a full tributary width.

This is not an engineered design, I am just providing
consultation to a contractor on how to use the IRC. 
But I want to be sure that I give them the right
advice.  Its still my preference to place posts over
the available bearing walls, but that's a moot point
here.

Thanks,
Jim Wilson, PE
Stroudsburg, PA

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********