Filling in hole in second story concrete floor.

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Old 08-12-15, 06:10 AM
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Filling in hole in second story concrete floor.

I'm relocating an exterior spiral staircase which goes from the ground floor up to a second story patio. Afterwards I'll be left with 54" diameter hole in the second story concrete patio floor which I need to fill in. What is the correct way to do this? My guess is it involves drilling and inserting steel Rebar into the face of the opening in some particular pattern, then bracing a form up to the bottom and filling from the top with concrete.

* What size Rebar?
* How far to drill in?
* What Pattern ?
* Type of Concrete?


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Old 08-15-15, 08:35 PM
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This is going to be a very difficult project for DYI. Since it's going to have to be very secured to allow people to walk on top of it it's very critical that it's done right. Without knowing a lot more than the information you provided is going to be impossible for anybody here to help you at all. While what you wrote up and basically what needs to be done the details are going to be very critical. Also, knowing how the existing floor was made is going to help an awful lot. Your best bet would be to consult a local structural engineer and have him review the situation and make recommendations. It won't be that expensive and well worth the cost.
 
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Old 08-15-15, 10:10 PM
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You could drill and anchor some No. 4 rebar at 6" centers into opposite sides of the opening, embedding them at least 4" into the existing concrete, and centered at the slab thickness. I'd use either epoxy or even neat Portland cement slurry for the rebar bonding agent, in the holes. Be careful not to drill or cut into existing tensioning steel in the slab while doing so, if it has any. Orient the bars to line up with and lap with bars from the opposite side of the opening (a lap length of at least 16" would be more than ample), such that they can be spliced together with tightly-wrapped tie wire. Then place an array of No. 4s perpendicular to the anchored bars, again at 6" centers, tying all the bar junctions with tie wire. For better bond, roughen the entire perimeter of the opening a bit with a bush hammer or chipping tool, then slap a well-braced, plywood form in place, overlapping the form against the existing concrete at least 6", all around the opening. Then it's just a matter of batching, mixing, and placing your concrete in the formed opening. Remember to consolidate it well, but too much such that the formwork gives way. Don't forget some cure on the concrete, too, if you want it to develop adequate strength, before stripping the form.

The foregoing is based on the presumption that the existing concrete floor/ceiling is sound and reasonably strong. If it's not, forget what I said, and call an engineer for an evaluation.
 
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Old 08-16-15, 03:18 PM
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1st time we did this was a pt. jervis, ny, bridge deck - 4'0 x 4'0 holes in 8" conc deck w/2mats of steel,,, we cored 1" holes & put back in 2mats of #6 bar,,, then we built a frame above the roadway w/4 chains holding form plywood up tight against the deck's underside,,,the chains were fed down thru 1" pvc pipe on ea corner maybe 2' inside ea edge,,, placed conc then dropped chains/forms down 40' to the riverbed then walked out into the wtr & picked them up,,, thought about parachute cord for a tether but that was faster,,, engineer LOVED the idea,,, sure beat supporting forms from the river up

fun job & we made a LOT MORE $$$$$$$$$$,,, caution: core drill the holes - no hammer drilling,,, & WEAR a safety harness, too

pro mtls + tools + methods + knowledge + skills = pro results
 
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