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bmwbykrydr 04-05-2010 06:56 AM

Need advice on pouring slab inside existing wall.
I'm going to be pouring a slab, 24'x32', inside a 24" knee wall that I've already poured. I won't be able to place a screed board around it to use like I would an exposed edge slab because I'm pouring the slab right up to the wall. How do I get the level of concrete correct, the slope, etc without a screed board?

I thought I could snap a chalk line but that will only get me close on the outside, along the face of the wall. The centers would then have to be eyeballed. Is that what pro's do, eyeball it?

I also thought I could set up string line posts along the outside of the wall that I level before the pour. As I go along the pour I put the strings up and use a ledger board all along the string as I go. That seems a bit slow and tedious, but I can see it working.

I'd like to hear what people think is the quickest and most efficient way.


concretekc 04-05-2010 10:04 AM

Concrete Slab
You can definetly use a screed board on this project and in order to use one here is what you are going to have to do. First get your height on your knee wall where the top of concrete is going to be and mark it and then pop a chalk line around the entire area so that will mark your concrete height on wall. After you have accomplished that you can pull a string line across various points and give you a point within the area to put grade pins (cut rebar) and bang them down to be even with the string line this will give you the ability to utilize your screed board by giving yourself a screed line to pull off of. When pouring your concrete you will place it up to the chalk line as best as possible then use a mag around the wall to get the concrete even with the chalk line this also gives you a level one foot area around the wall to pull your screed board off of. Hope this helps you out.

Aggie67 04-05-2010 10:11 AM

We build concrete containment dikes, which is pretty much what you described. We do the turndown slab first, then the walls. A lot easier screeding it. But there's no reason you couldn't pour it after the walls are in. Just use string lines and a decent screed. Definitely not a one or two man job. Two guys on the screed, two or three guys raking, a guy working the chute (or two if you're pumping or buggy lugging), then two or three guys out there finishing. And for that size slab, they had better be experienced. That's a little over a full load, and both loads have to go down one after another. No dilly dallying. You can lose a pour quick if you don't know what your doing.

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