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9/30/2011 3:30:17 AM
When replacing all old sheathing with new sheathing and the rafters spaces are 24" o.c. what whould the the thickness of the sheathing be according to the 2009 IRC?
Also, Whe doesn't the City's that are supposed to be inforcing these codes don't enforce them?
9/30/2011 8:06:20 AM
Welcome to the forum.
According to 2009 IRC, Table R803.1 Minimum thickness of "lumber" roof sheathing; rafter spacing 24"; would be 5/8".
and, for Wood "structural panel" sheathing (R803.2.2 Allowable spans); you would go to Table R503.2.1.1(1) to determine minimum nominal panel thickness.
Many code requirements are not inspected. Section R109 Inspections; are generally considered "required inspections" by the Building Safety Department; and some of those are excluded by amendment or by the building official. R109.1.5 gives the building official authority to conduct "other" inspections. Most cite lack of inspectors and/or time restraints as reasons for not conducting some inspections.
Always contact your local Inspection department for amendments and local requirements.
Hope this helps,
Retired Texas Combination Inspector. Location Oklahoma.
9/30/2011 9:35:49 AM
Pay attention to what UB is saying... "lumber" which is the plank type sheathing is required to be 5/8" where "structural panel" is your OSB type of sheathing, which could be as thin as 3/8"
I've had other inspectors call me before and say "You know what I just read??? Desking on houses have to be 5/8" " I said... No! that's when lumber is used!
Ohhhhhh now I see!
10/4/2011 9:41:20 AM
7/16 " osb or plywood is the minimum you can use without edge support. some departments do not have the man power to do roof sheathing inspection, inspectors can not see everything and assume that the builder knows enough to do some things right. The stamped span rating on the sheathing will over ride the code.
10/5/2011 10:15:06 AM
10/5/2011 3:46:20 PM
Depends on the roof load see TABLE R503.2.1.1(1)
I am in a minimum 46 psf snow loads (live load) for roofs. According to the table 7/16" OSB or plywood with a 24/16 rating installed with 24" oc trusses/rafters is only good for 40 psf so 15/32" or 1/2" are the minimums in my jurisdiction.
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