cost comparison 9steel0 question

huangyhg

cost comparison (steel) question
steel framed building - typical bay size is 20'x20'.
which is more economical for a roof framing system-
a.  1 1/2" roof deck on w10x12 at 6'-8" o.c.
b.  3" roof deck on w12x14 at 10'-0" o.c.
i think the 3" roof deck would be a better solution, even though 3" roof deck would cost more.  you have fewer beams, (even though they are slightly heavier), fewer connections.  heavier roof deck would take more labor to install, but i'd imagine that would be at least offset by installing fewer beams.
anyone have any thoughts or similar experience?
thanks.
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lppe:
i posed a very similiar question to a fabricator and erector (teamed up for a design build project) one time. 30' x 42' bays, with eithier beams at 10' spacing and 3" deck, or beams at 6' with 1 1/2" deck.
their response was that the costs would be virtually identical @ approximately $5.00/sf
however, substituting open-web joists for the beams reduces the cost to about $4.00/sf.
obviously, those costs are very project specific, and may not be representative of your situation, but it does give an idea of the magintude of savings that can be realized from using joists.  
one thing to consider, if the owner is going to need an fm rating for their insurance, there are no 3" metal roof decks that have an fm rating.  this alone would cause the use of 1.50" deck to be the right choice.
in these areas... the 1-1/2" deck is generally more economical and 6'8" +/- is generally the max span for 0.030 cnt.  it can be used for about 7' max, depending on loading, but is very bouncy for this span...
dik