huangyhg

deep roof deck
i've got a 17 foot span that i'd like to use 4.5" metal roof deck. is this metal roof deck hard to get, or is it just as prevalent as 1.5 and 3" metal roof deck? any premium in cost?
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i just used 4 1/2" deck on a project in the midwest - yes there's a cost premium from 1 1/2" deck - you could call a few deck manufacturer's to find out. but it was available.
here's a list of some deck manufacturers. i don't re
thanks, jae. i have an epic catalog in front of me now. i guess the question now becomes this - is the cost increase in deck offset by the decrease in half the bar joists now needed?
that is going to be determined by a lot of different factors including what the client wants in the way of space, "look", skylights etc.
i just did a 60'-100' cmu brg wall building w/ longspan jsts spaced @ 10'-6" o.c. and 3" deck and the client definitely wanted the wider spaces and the cost was about a wash one way or the other.
that's right - we used the 4 1/2" deck more for dealing with the nature of our specific problem, not totally for an economic purpose. we were framing a light roof over an entrance ramp to an underground parking area where the long side of the roof connected to an existing wall. we needed a roof with minimal connections to the wall and also wanted to avoid birds nesting on the beams and deck gaps.
so we specified the 4 1/2" deck, supported by tubes (no flanges for nests!) and plugs to go into the flute openings over the beams.
note that with the deeper deck, you are generally working with narrow strips of deck, not 30" or 36" wide sections. so the labor is more intense as well.
don't forget that diaphragm strength may be significantly reduced.
i like b. csi above. their deep-dek offers an overlapping flange that can be screwed together from above so that there is no visible interuption of the surfaces from below. yes, the material will cost more than the 1.5 or 3" deck, but not only are you eliminating the structural complexity to support it, you eliminate the skilled welder and the special inspection of the weld to tie it into a shear panel. as for the 1' coverage, that to me gets the weight down to the place where you can handle the part without having to have a crane. it may be more labor intensive but to me it looks like it may be with fewer laborers at lower cost. i am planning on using 6.0" 18ga. deep-dek at a 32' span. part of this is possible due to no snow load in phoenix, but i wonder why the product is not in more widespread use. is it relatively new to market? or do we sub-optimise? i figure on the 13,000 sf building i am designing an inch of wall height is $1000. the dominant system here seems to be trusses made of angle iron with shear web bracing made of angle iron with the ends flattened into a "u" to fit between paired spar caps of angle iron. to me this looks like a really miserable welding/inspection/weld affected zone on spar cap/elastic stability of shear web situation that leaves me wondering. the axial splices on the spar caps are butt welds reinforced by lengths of rod laid in the angle iron and stitch welded. yeah the test article might have gotten the design a sji certification, but did you ever read the sji weld quality requirements? 1/16" of undercut? on 3/16" or 1/4" thick angle iron you might want to do better. oh and that structural depth required looks like $2/sf to build the walls to support it.

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