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Span Tables in the IRC for exterior decks

Rick18071 said:
I don't think the IRC tables are for treated and wet lumber with snow on it.
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There is no table for lolly columns either....or any posts for that matter......

I was kinda being sarcastic above, as much as the IRC is "supposed" to be a one stop shop for building a house...it is really not....Or at least not for the houses being built today....

And then playing devil's advocate...Where does it say "wet" or "dry"?
 
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The IRC span tables are for dry applications and were never designed for exterior decks.

The IRC clearly points you to the WFCM/NDS in many instances but I still know guys that don't own a WFCM

If you don't own a WFCM or use the DCA-6 (changed in July 2013 due to SYP problems) then I don't know how you are actually doing your job.

The bottom line is that wet use tables and adjustments are necessary AND you should not be using those tables in the IRC for wet use decks.

Every year I rant about this. But still…………………….
 
I've been in the jurisdiction since 97, and we have had one deck failure, and it was due to detachment at the ledger/structure. Have worked locally in the trades back to 76, have never heard of a deck failure due to overspanned joists/beams here.
 
There are plenty of charts to choose from within the IRC that will work. Personally I would not use the floor span charts for a deck I would use Table R802.5.1(7) since the deck is exposed to the additional snow loads and snow drifting that the IRC does not even address.

In reality we use StruCalc and don't bother with the Tables when checking spans.
 
fatboy said:
I've been in the jurisdiction since 97, and we have had one deck failure, and it was due to detachment at the ledger/structure. Have worked locally in the trades back to 76, have never heard of a deck failure due to overspanned joists/beams here.
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Not the point. Not the point at all.

Do you want to continue to set precedence with picking and choosing what codes you enforce.

That excuse is as bad as "I've been doing it that way for 30 years" which we hear all too often.

:)
 
Jeff.....Where in the IRC does it say that the tables do not cover exterior decks? Or that they are for dry use only? He provided a clear code path to use those charts for a deck. It's not what I do, but 502.3.2 seems to cover it....Table 502.3.3(2) specifically references balconies and there is no mention of wet or dry....
 
steveray said:
Jeff.....Where in the IRC does it say that the tables do not cover exterior decks? Or that they are for dry use only?
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"Cuz he said so, and he's been saying so for 30 years. :devil

:popcorn

As a point of reference: 2009 IRC Table 502.3.1 (2) Dead load 20 psf lists a 2x10 #2 syp 16" o.c. max span as 14' - 8"

The DCA-6 addendum published May 2009 list 2x10 sp 16" o.c max. span as 14" - 0"

That is pretty insignificant. And, as FB said, not likely to be a factor in a catastrophic failure
 
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I use DCA6. It is also pretty handy as a hand-out. While you might get a good answer for joist spans out of IRC I have yet to find a good answer for deck beams in the IRC so the DCA6 is a one stop shop for me. It might be a little more conservative (especially on footings) but it is an easily referenced document. I do occasionally use the WFCM but As JAR said, most people don't have it so I find it easier just to stay with the more easily understood "just for decks" manual.
 
Try explaining to a homeowner that his Home Depot deck plan doesn't meet code because he is building in a jurisdiction with an 80psf ground snow load. His deck plan was from south Jersey.
 
I am not saying there are not conflicting charts, and in some parts of the country it may be better suited, and personally I like it...........point being, what is adopted? If I turn down a design, or inspection, based on DCA6, have I adopted it? No, I adopted the 2012 IRC, down in flames at the BOA.
 
I am not saying there are not conflicting charts, and in some parts of the country DCA6 may be better suited, and personally I like it...........point being, what is adopted? If I turn down a design, or inspection, based on DCA6, have I adopted it? No, I adopted the 2012 IRC, down in flames at the BOA.
 
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