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Concrete Deck

 
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Old 02-15-2015, 08:41 AM   #1
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Concrete Deck


I have a concrete floor to pour on an elevated metal. Plans call for 3 1/2" of concrete. The architect did not call for any reinforcing other than fiber mesh. Any thoughts?
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Old 02-15-2015, 08:53 AM   #2
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Re: Concrete Deck


if you deviate from the approved plans its on you... if your really concerned about it bring it up but you will more then likely be told to stick to the plans.

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Old 02-15-2015, 08:53 AM   #3
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Re: Concrete Deck


Seems O.K. to me but I am not the engineer on the project.

What gauge does it call out for?

Andy.
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Old 02-15-2015, 09:09 AM   #4
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Re: Concrete Deck


RFI to the engineer.
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Old 02-15-2015, 12:11 PM   #5
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Re: Concrete Deck


I have seen it done a lot of times. The strength is in the joists, and the dispersing of the load. The concrete is the cheapest, stiffest deck available.
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Old 02-15-2015, 12:53 PM   #6
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Re: Concrete Deck


We are doing the same right now, about 5000' slab and only 2.5" of concrete above the highest ribs, 4" from the lower part of the pan. Our joists are 5' o.c. too
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Old 02-15-2015, 01:17 PM   #7
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Re: Concrete Deck


Since the decking is only 9/16" the joist spacing is probably no more than a few feet, if that. This type of deck is typical for a mechanical mezzanine.
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Old 02-15-2015, 03:07 PM   #8
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Re: Concrete Deck


Yes, I'm not so concerned about the load &/or joist spacing. That has all been through engineering. The joists are on 2'0 centers. Slab is roughly 8000 sf. I was referring more to how the 3000 psi concrete (which was spec) would react and perform at 3.5" on the galvanized deck with no rebar or wire mesh. Rebar would be difficult, because with only 3" of concrete there would not be enough cover unless it was laid on the bottom. At that point, what is the use?
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Old 02-16-2015, 09:47 AM   #9
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Re: Concrete Deck


9/16" decking? Ha, never seen that before.
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Old 02-16-2015, 09:52 AM   #10
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Re: Concrete Deck


9/16 allows for a stiffened pan, and is not for structural, per say.

I have seen decks with welded wire panel reinforcement, but in thinner slabs, rebar pushed to the bottom of the slab could actually cause a structural problem.
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Old 02-16-2015, 06:25 PM   #11
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Re: Concrete Deck


Pretty normal, its interior so not seeing freeze/thaw. We did a 110x125 church the same way. The fibermesh is enough
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Old 02-17-2015, 03:39 PM   #12
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Re: Concrete Deck


The ones we have been involved in have had wire mess in the pour. We've always done EPDM between the decking and the concrete.
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Old 02-25-2015, 07:46 PM   #13
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Re: Concrete Deck


pour it according to the plans...ditto what mark said.
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Old 02-26-2015, 05:39 PM   #14
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Re: Concrete Deck


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pour it according to the plans...ditto what mark said.







Shortly after Falling Water was built and the cantilevers started to sag,Frank Loyd "Wrong" blamed the problem on the concrete contractor.....he added more steel to the pour.


P.S. Even though he reasoned the steel was insufficient and added more,the architect needed someone to blame.
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Old 02-26-2015, 06:08 PM   #15
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Re: Concrete Deck


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Shortly after Falling Water was built and the cantilevers started to sag,Frank Loyd "Wrong" blamed the problem on the concrete contractor.....he added more steel to the pour.





P.S. Even though he reasoned the steel was insufficient and added more,the architect needed someone to blame.

I was just reading about those sagging cantilevers. Deflection eventually reached 7 inches over 15 feet!
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Old 02-26-2015, 07:12 PM   #16
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Re: Concrete Deck


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Originally Posted by fjn View Post




Shortly after Falling Water was built and the cantilevers started to sag,Frank Loyd "Wrong" blamed the problem on the concrete contractor.....he added more steel to the pour.


P.S. Even though he reasoned the steel was insufficient and added more,the architect needed someone to blame.
I thought it was worse than that, the contactor told the homeowner that he thought there should be at least double the steel. The HO told Wright and he freaked out as he took it as an insult. The contractor went ahead and doubled the steel.

Then after it was poured on of Wright's employees realized his load calculation was half of the actual load and double the steel would be required.

But the damn thing sagged anyway.
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Old 02-26-2015, 09:45 PM   #17
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Re: Concrete Deck


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I thought it was worse than that, the contactor told the homeowner that he thought there should be at least double the steel. The HO told Wright and he freaked out as he took it as an insult. The contractor went ahead and doubled the steel.

Then after it was poured on of Wright's employees realized his load calculation was half of the actual load and double the steel would be required.

But the damn thing sagged anyway.
I believe the concrete contractor was an engineer (by education?)...
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Old 02-27-2015, 05:39 AM   #18
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Re: Concrete Deck


Use dimpled tin pans so the tin is bonded to the deck...., 4 or 5kPSi crete would crack more but be stronger.... sealing the crete or covering as soon as it can be walked on with out damaging it would give maximum strength for the $

methods of fastening steel to joists make a large difference and the length of the sheets, the greater the # of 3 span vs 2 span the stronger the deck at the = cost of materials/labor mostly

Unskilled labor will over load the deck/trusses while pouring creating "pot holes" of way over thickness, I NEVER walk under illegals/lazy/under manned pouring floors/roofs....

there is an elementary school in Iowa that has 12" thick spots on a 5" design deck, bowed decking on bowed red iron way past D= L/300....

If the ceiling is hanging several inches below the bottom of the trusses, up size the truss depth and use fewer with a tiny bit thicker floor, saving $$ for the GC and big money for the mechanical, Hvac and electrical subs.

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Last edited by Fouthgeneration; 02-27-2015 at 05:46 AM.
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