Porch slabs

I've got several porches/patios which will project from the main structure of my house. The side walls will each be roughly 6-7 block courses high. The floors will be concrete slab with some sort of tile/stone topping. I'd rather not try to fill these rather large boxes with dirt in order to pour a slab on top. Is there an alternative method of supporting the concrete floor that won't break the bank?
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Reinforcing steel.
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MichaelB
www.michaelbulatovich.ca
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snipped-for-privacy@yahoo.com wrote:

Permanent metal forms. Light weight deformed metal sheets used as concrete forms and left in place. Some are available with studs or other mechanical connections to the concrete. TB
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Why not use dirt? Find yourself an excavator that needs to dump some dirt. He'll have to pay a place to dump it or give it to you for free. If you do this method make sure you use rebar in the slab because as hard as you try, you will not compact the dirt enough to keep the slab from cracking. An alternitive is stone, that you will not find for free. How ever you may be able to find a local black top contractor who has some left over that he will give you a deal on. Lou
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the largest will be roughly 12' wide by 23' long.
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As Michael & tbasc both suggest (you need to combine both msgs') you could use pan deck(Q-Deck) with rebar to span the 12'. With respect to that, you'd need an end wall bearing support (more block?)against/beside the building. Depending on the slab depth, you 'may' need temp support for the midspan of the deck until it cures. In essence, it's a deformed metal deck with 1.5" deformations in it and comes in 36" widths and is at least 20 gauge in thickness. Common use is industrial construction. An example, albeit not exact is here; http://www.metaldecksupply.com/products/product_detail.asp?Inventory 5
Essentially you place the deck and install #4 rebar (1/2" dia) midway between the top face of the deck & the exposed surface of the slab. 100% ties on the rebar @ 8~12" on center both ways. 6-6/10-10 WWF [WWF= welded wire fabric/commonly called wire mesh] [6-6= 6" squares/10-10gauge wire both directions] would substitute but the rebar would be better. IMHO
Dan

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I suggest to do the slab on grade system. It will cost you less and much easier to construct. You can use welded wire fabric for reinforcing in the slab on grade over the compacted fill. You should also think about reinforcing the concrete block walls even if they are 48 in high. They will become retaining walls for the compacted soil pressure. The wall foundation will be the simplest.
The other way will be either composite concrete steel deck with the 12 foot span it might be 3 " deck with 3" concrete . If not the next most expensive way is to form a structural one way concrete slab to span the 12 feet span around 5 to 8 inches thick you will then have extensive reinforcing in the slab. You will also have to provide some sort of drainage with the space under the structural slab or steel deck/concrete slab. You might even have to have an access door under the slab. Your foundation for the walls will also be different.
Oh don't forget a railing if you have more than 2'-6" height from the slab floor to the finish grade on the outside of the slab.
Hope this helps.
CID...

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In a previous post snipped-for-privacy@yahoo.com wrote...

Used closed cell foam (think Styrofoam). Find the high strength (100 psi) stuff.
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Bob Morrison, PE, SE
R L Morrison Engineering Co
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Bob, I'm not sure I'm following. You mean to say I'd use the foam boards in lieu of wooden/steel forms to form the pan? Or just as insulation on top of earthen fill and below the slab ?
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In a previous post snipped-for-privacy@yahoo.com wrote...

I recently learned that an engineering firm that I respect recommended the use of stacked Styrofoam blocks to be used as the support structure for concrete stadium style seating. They simply stacked blocks to make the rough shape then formed and poured the steps, seating pads and access ramps to make the seating. No shoring required. No fill required.
In your case, level out the ground, stack Styrofoam up to the bottom of your "slab on grade" (say 4"-5" below finished surface). Pour concrete on top of the Styrofoam. Leave the foam in place. It won't rot.
This method will be more expensive than placing and compacting dirt, but probably much easier for a small area. One other option is to fill the area with controlled density fill (CDF). This is a low strength concrete often used for filling utility trenches. You will have to build side forms to contain this material.
Or you could do as few others have suggested: pour on top of a steel corrugated form deck. Leave the deck in place. In this case your slab will be an elevated slab and would have to be properly engineered to span the distance between support points after the form deck corrodes away.
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Bob Morrison, PE, SE
R L Morrison Engineering Co
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