# Suspended Slab



## FramingPro

BC Carpenter said:


> when I was doing it we would pour all the columns first on a floor, then when all the columns were ready start with flytables or free forming with aluminum scaffold frames, braces, then aluma beams on top, 4x6 stringers on top of that then 3x4 form ply on that,
> 
> the "beams" would be about eight feet to the next one, which would be a difference in width from sixteen inches to 3 feet, each "beam" centered to a column, each flytable would be the width of one beam. Once the floor was poured the tables would be rolled out, or free form taken down, go up to the next floor. Lots of rebar, can't tell you specific spacing.


im starting to become interested in forming too. i have a question for you. about highrise forming. So i see there is posts every 8' feet or whatever and on top of those are steel beams. then across those goes the 4x joists and then nail formply? i think so but near me i only see steel joists.


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## KennMacMoragh

Are you talking about posttension slabs? I've formed those up before, and I've inspected them. There's a lot that goes into them, but I'm not sure which kind of slab you're talking about.


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## JustaFramer

FramingPro said:


> im starting to become interested in forming too. i have a question for you. about highrise forming. So i see there is posts every 8' feet or whatever and on top of those are steel beams. then across those goes the 4x joists and then nail formply? i think so but near me i only see steel joists.


There is a nailer strip


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## FramingPro

JustaFramer said:


> There is a nailer strip


on top of the steel joist? and i guess they only tack the formply


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## BC Carpenter

FramingPro said:


> im starting to become interested in forming too. i have a question for you. about highrise forming. So i see there is posts every 8' feet or whatever and on top of those are steel beams. then across those goes the 4x joists and then nail formply? i think so but near me i only see steel joists.



When I was doing it, when we would freeform it (opposed to flytables) we would put up our frames and braces (or posts, depends on the system) after that aluminum beams would sit on top of the frames, with seats holding them in place, that slid into the top of the frames. There is a nailing strip on top of the aluma beams. But then goes the 4x6 lumber on top of the aluminum, then the formply on that

. When stripping, the labourers just have to lower the feet on the frames, and the whole thing can be brought down. 

Just like with flytables when they bring them out, hook them up and take them to the next floor. There are a lot of different systems out there now that i'm not really familiar with as I don't do commercial work anymore, but that was the basics when I was doing it a few years ago.


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## FramingPro

BC Carpenter said:


> When I was doing it, when we would freeform it (opposed to flytables) we would put up our frames and braces (or posts, depends on the system) after that aluminum beams would sit on top of the frames, with seats holding them in place, that slid into the top of the frames. There is a nailing strip on top of the aluma beams. But then goes the 4x6 lumber on top of the aluminum, then the formply on that
> 
> . When stripping, the labourers just have to lower the feet on the frames, and the whole thing can be brought down.
> 
> Just like with flytables when they bring them out, hook them up and take them to the next floor. There are a lot of different systems out there now that i'm not really familiar with as I don't do commercial work anymore, but that was the basics when I was doing it a few years ago.


nailer strip is to toenail i guess


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## JustaFramer

FramingPro said:


> on top of the steel joist? and i guess they only tack the formply



They are not steel. Mostly made of aluminium. They are formed with a slot to allow for a replaceable wood nailer. 

There are makers of steel forming materials. Efco comes to mind with their deck forming set-up. With E-beams and super studs. It is possible to spike a nail through a E-beam.


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## FramingPro

JustaFramer said:


> They are not steel. Mostly made of aluminium. They are formed with a slot to allow for a replaceable wood nailer.
> 
> There are makers of steel forming materials. Efco comes to mind with their deck forming set-up. With E-beams and super studs. It is possible to spike a nail through a E-beam.


o true, i only see from the bottom so.. but is the form ply completely nailed off to joists or just tacked?


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## mudpad

FramingPro said:


> o true, i only see from the bottom so.. but is the form ply completely nailed off to joists or just tacked?


Just tacked. The weight of the concrete will flatten out any warped ply. 3/4 formply lays pretty flat anyway.


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## FramingPro

mudpad said:


> Just tacked. The weight of the concrete will flatten out any warped ply. 3/4 formply lays pretty flat anyway.


thats what i thought, i don't see any framing guns so that lead me to believe its just tacked and not nailed off. do they normally reuse the ply after that. they must because formply is so durable


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## mudpad

Yes, normally can get at least 2 or three uses out of it, and more if it is a slab or wall that gets a finish over it (or under it as the case may be) I have some pretty rough panels we are using on some retaining walls that have probably been used 8 or 10 times, but these get brick on one side and dirt on the other, so what the heck as long as they hold concrete!


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## mudpad

FramingPro said:


> thats what i thought, i don't see any framing guns so that lead me to believe its just tacked and not nailed off.


Form erectors wouldn't know what to do with a framing gun, other than shoot themselves in the foot. Everything just tacked off. 22 oz estwing hammer is the standard for the industry around here. 

I always say you only have to remember 2 rules for concrete forming. 
1.) it's gotta hold concrete
2.) you gotta be able to wreck it

The fewer nails the better when it comes to rule #2


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## cleveman

So let me get this straight.

I can form up, say a 24' wide pour with 2x4 joists spanning 4 feet, then pour the concrete either 4 or 6" thick with 6" woven wire mesh. After the concrete cures, I can strip the joists and panning. How far can 4" of concrete span? How far can 6" concrete span? What thickness would I need to span 12'?

Will it help to use some rebar as well as the woven wire mesh? 

Is there some published span chart for type of concrete, reinforcement, and thickness of concrete?

Thanks for the thread.


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