Faster Slab Forming

Justbuilding

Just curious how some of you may be doing your thickened edge slabs for slab on grade. Historically we make some beautiful form panels that make great looking footings and slab edges, then the excavator buries 90% of all that great looking formed concrete. This past job we used 2x 10 staked to grade and stapled the vapor barrior onto it to use as our form edge. Staked and aligned the hell out of it and placed it. We beat the hell out our budgeted schedule, set up a 24k sqft of slab with 3 guys in just under a week, 2 foot thickened edge.

What/ how do you guys use to go fast?

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thom

Around here it's done both ways.

The quality guys put in footings, then stems. The plumber then does his underground. Finally the concrete guys come back and poor the slab.

The cheap guys do a monolithic pour. Hopefully the lines (string) the plumbers pulled off of line up exactly with the lines the concrete guys laid out their foundation with.

Justbuilding

Residential is a different animal, while stem walls are not unheard of, typically that is not a commercial application, for larger buildings anyway. This particular building has almost 600 yds in spread footings and pile caps and 580 yards in slab and thickened edge.

Super-Mike

Around here we build it like the engineer specifies in the prints. If it's monolithic, it's monolithic.. if it's not it's not. More often than not it is.

Secondly.. Justbuilding: Were you saying that you form your slab footings too? Because that would seem like just a big waste of money.

And yea, 2x material and turn buckles is how we do it. Unless it's something small, building box forms is for suckers.

K2

I would think frost and some other variables woud get into the equation. The last one i was on was 40 ft cassions @15 ft centers into a 36 inch grade beam with a mono pour over...


And Thom, the commercial boys around here work off of grid lines so if your dead nut to the grid lines then it wouldn't matter if the concrete guys were a foot off... I made the mistake of using the "outside of the concrete" for a measurement one time. That mistake was worth a couple of grand at that time.

Justbuilding

We used to build box panels for everything, spread footings slab edge forms, we were really proud of what you couldn't see. Some of that was fear trying new techniques, this is just one way that I've recently tried.

Super-Mike, are you stacking the 2x or using expanded metal for thickened edges or?

K2 were you involved in the concrete work? If so how was the slab edge formed?

Super-Mike

When we have large turn-downs for very thick edges we use Symon forms. If it's smaller slabs usually the turn-down doesn't warrant anything larger than a 2x12. If we got a little gap, throw some dirt in it and call it good.

You know, you might want to look into that for your next slab and see how fast that goes. It's probably the fastest thing to form with, and it does not use near as many turnbuckles as 2x.

They are not very expensive to rent and they will produce a slab edge that is just about as good as building boxes (you get a small ridge where the forms are put together.)

And yes, technically they are wall forms.. but there is more than one ways to skin a cat, so my father always says.

joasis

We go monolithic when at all possible, and I don't think it could be called "cheap" if done correctly.

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Super-Mike

I don't like using stem walls either. A: who has the time to wait around for them to be built and B: they are no where near as strong as a properly reinforced 12" thick edge of 4000 psi concrete.

But then again, like I said.. I do what the engineer wants. It's what they are hired to do.

Justbuilding

All our work is thickened edge, at least 18" thick, the one in the picture is 2'. Haven't seen anything less in a long time. I have used symons forms, labor intensive (comparatively), and one thing I liked about this is that the excavation didn't have to be perfect, or constantly screwing with the forms, digging out or wedging up for the joints. One reason I used so many turnbuckles is that I wanted this edge to be as perfect as we could get it for the stem wall that sits on top. If it was just going to be framing, I probably would have used less turnbuckles.

Norm Yeager

I've done several 3-500 yard slabs with monolithic edge footings, some with brick ledges, some without. All designed by P.E.
. We drive 3' steel pins to a string line appx. 6' o.c. Whatever the stepdown is for the brickledge, that's the thickness of the edge form. In this locality, typically 8". The boards are screwed through the steel pin holes with DW screws. The entire form on one side of the building is screwed together and laid on other steel pins laid accross the trench and measured flat
before being stood up and screwed to the driven stakes- many times over 100' long. After all the forms are "standing we'll make 2X stakes and drive them at appx. 45 degrees on the o/s of the forms (nailing them with 16d duplex) to straighten them at appx. 3' O.C. After pouring all the stakes and forms are pulled (usually just before slab is finished) When slab is finished, with enough manpower , you're done with everything on the truck/trailer to move to next job.