Need Help Framing a Turn-Down-Slab

[LittleBittyBigJohn]

Title says it all. I have my pad built and I think there may be a picture in my shop thread. I wanted to break this thought out so there would be more visibility and hopefully I'll get some good thoughts. I'm planning on renting a mini-x this weekend and getting it ready for concrete. I have 2 things I need help with.

1) I want to dig the footer turn downs to the finished size and add forming above instead of digging wide and using 2x12 boards all the way to the bottom of the footer. This way I can save money on boards and get a little deeper footers. But, I've never formed anything and I don't really know how to make it all line up and hold together.

2) How do I get 4 runs of re-bar to hold together. I know there are rebar chairs that will hold the bottom 2 off the bottom but I don't know how to elevate the top 2.

 

[scootr]

We always used wood stakes and tie wire. The outer form is set and the grade is finished. Then a wood stake is laid across the footing resting on the form board and the slab grade. Tie wire suspends the rebar from the wood stake. The footings are poured first, the wires are cut, wood stakes removed, and the slab is poured all in a single pour. Remember to overlap your rebar joints 40 times the bar diameter.

 

[paulsharvey]

Typically, if you want 4 rebar, you would tie it up like a box, and place it all together. easiest way, would probably be #2 smooth ties, in a square, and tie your 4 bars to that. You can tie the boxes up as sections, and overlap (check your local spec for requires overlap)

 

[scootr]

That is some serious overkill - I'm certain the engineering simply calls for 4 bars - no hoops

 

[paulsharvey]

You could take a #3 rebar, and wrap it around a 6x6 or 8x8 timber, making the squares, order them from any rebar supplier, use a rebar bender, or even the ball on a trailer Hitch (hard to keep it exactly uniform). Once you have your squares, tie one every 4 feet or so, with the bottom 2 #4 bars (odd they spec 4-#4s, I stead of 2-#5 or 2-#6), then put your

top 2-#4s, tie them as well. The 'beam' will be kinda floppy, so don't think you can lift/place more then max 20ft at a time. The bottom of the box will need supported by chairs or a'dobe' bricks. (basically a solid brick with a 2 tie wires in the top of it.

Another possible option is driving 2 verticL rebar stakes, and tieing horizontal bars. Issue is, the stakes will be exposed to rusting (bottom of stake js in plain soil not concrete), which will eventually wick up, and over the years (or decades) allow your horizontal bars to corrode.

 

[paulsharvey]

A ghetto option, (not endorsing), is pour 3-4" of footer, lay bottom 2 bars, pour next 4" and add 2nd 2 bars; not how I would do this, but in residential type work, I'm sure it happens a lot.

Edit: I don't mean pour, let set, add bars, and pour new on old, that is beyond ghetto, and is a a disaster. Do not do.

 

[paulsharvey]

You can also look for some 4" tall dual bar chairs, and then some 8" tall dual chairs, and not tie anything but laps and corners.

 

[paulsharvey]

Looks like a #3, 6"×8" rectangle stirrup is 4.08 Cunuckistan Copek, or about $3/each. Trouble will be finding them in stock, but Whitecap and many other custom bend rebar.

 

[Chewwy]

Title says it all. I have my pad built and I think there may be a picture in my shop thread. I wanted to break this thought out so there would be more visibility and hopefully I'll get some good thoughts. I'm planning on renting a mini-x this weekend and getting it ready for concrete. I have 2 things I need help with.

1) I want to dig the footer turn downs to the finished size and add forming above instead of digging wide and using 2x12 boards all the way to the bottom of the footer. This way I can save money on boards and get a little deeper footers. But, I've never formed anything and I don't really know how to make it all line up and hold together.

2) How do I get 4 runs of re-bar to hold together. I know there are rebar chairs that will hold the bottom 2 off the bottom but I don't know how to elevate the top 2.



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Your project is almost identical to one I had done over 20 years ago. I did not do it myself but paid close attention to the work that was done.

The area had been cleared, flattened, and leveled (supposedly) prior to the form work.

The area was laid out using 2x4 corner posts and string pulls to designate the area to be formed and poured. A transit was used to establish the string heights as well as to ensure they were level. 2x6s were used to make the forms using 2x2s posts pounded into the ground every 4 ft as backers to the forms.

The footer area was dug by hand (quite a feat in our red clay). The dirt that was removed was used in the areas where the forms and existing grade had gaps. The rebar in the footer were supported by pieces of broken bricks both at the lower level and the upper level.

The total pour was 24ft x 40ft and was done in two pours over two days. After the concrete had cured for about a week, the area was cut into 4 sections (one lengthwise and one widthwise using a diamond saw) to minimize future cracking. To date, there have yet to be any cracking in the finished pad.

 

[paulsharvey]

On item #1; you are correct, earth form bottom/inside, form boards on the exposed portion of the outside. Spray with diesel or release agent will make stripping easier. Account for some additional waste/over run on concrete, maybe 10% of the FOOTER total to account for the less exact dimensions when earthformed.