What is the first code year that required minimum 7/16" roof decking

[Corbin@roofsonly]

Hello all,

I live in Austin Texas and my boss has tasked me with figuring out what year Austin adopted the code that requires minimum 7/16" roof decking to be installed for asphalt shingles. Austin tends to adopt new code very quickly so I'm assuming that whenever that became code is about when Austin started requiring it. I can not for the life of me find what code year made that the minimum requirement. Can anyone please help me with this?!?!?!

Thank you in advance!

 

[Yankee Chronicler]

I'm not sure what you mean by "for asphalt shingles." For as long as I can remember, the IRC in chapter 8 has deferred to Table 503.2.1.1(1) for minimum roof sheathing thickness for wood structural panels (plywood). There was a change to that table between 2006 and 2009, but it didn't affect roof sheathing for spans of 24 inches or greater, and it doesn't make 7/16" the minimum for anything under 32" o.c. unless the panels are rated for both roofs and subfloors.

Here's the 2006 table:



Here's the 2009 table:



And here's the 2021 table:

 

[steveray]

Still not required in the 2021 code.....Just span rated....

 

[Yankee Chronicler]

Still not required in the 2021 code.....Just span rated....

I disagree. The table includes a column for minimum thickness as well as for span rating. If the thickness didn't matter, why was it changed from 5/16" to 3/8" from 2006 to 2009?

 

[steveray]

I disagree. The table includes a column for minimum thickness as well as for span rating. If the thickness didn't matter, why was it changed from 5/16" to 3/8" from 2006 to 2009?

I meant 7/16 not required...if it is thinner, or thicker for that matter, it absolutely needs to be rated for the span in question....

 

[Yankee Chronicler]

So let's get back to the original question:

I live in Austin Texas and my boss has tasked me with figuring out what year Austin adopted the code that requires minimum 7/16" roof decking to be installed for asphalt shingles.

Where does the Austin code require 7/16" minimum for use under asphalt shingles? Looking at the Austin residential code in UpCodes, Table 503.2.1.1(1) appears to be the same as in the ICC IRC. The table allows 3/8" structural wood panels for roof sheathing with spans up to 24 inches. (With edge support. -- what we call "plyclips.")

 

[Joe.B]

This is a pretty typical misunderstanding that I see quite frequently. It probably went something like this:

(The following story is based on a true story; however, identities have been changed to protect the innocent.)

On one fine November day in 2012 Jim Bob and his crew showed up to do a roof on a newly constructed house. They didn't bother looking at the plans because, after all, they have been doing this for 30 years. They start to sheath the roof with 3/8 plywood, just like they've always done, and the GC calls up to them: "Hey boys, plans call for 1/2" plywood."

Jim Bob knows better, and says: "Well that's just horse pucky, them plans are wrong. All I gots is 3/8's, you want this roof done or not?"

GC is no greenhorn, so he tells them: "Look, codes changed, plans call for 1/2" and so does the contract you signed, so get that crap off my roof and do it right."

From that day forth Jim Bob and his crew knew the code changed and only ever brought 1/2" plywood to his jobs.

 

[Inspector Gift]

...From that day forth Jim Bob and his crew knew the code changed and only ever brought 1/2" plywood to his jobs.

Great story, Joe! Thanks for the laugh and making my day better!