Need Help Framing a Turn-Down-Slab

[LittleBittyBigJohn]

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.

You are saying I can just dig the lower portion of the footers and not frame the bottom 12"?

 

[paulsharvey]

Around here, that design is typical, monoslab, and although you might pour the FOOTER portion first, you will pour footers and slab as a single placement to avoid any cold joints. IE, truck#1 pours (or pumps) the entire perimeter FOOTER, truck #2/3/4 pour the flat work, and everything is a single, monolithic slab, or thickedge slab. Probably 95% of homes in this area are poured that way. Stem walls are almost unheard of, here in N Fla, but we aren't dealing with freeze-thaw, or mountain sides, where a stem wall can 'step' up or down on the grade.

 

[paulsharvey]

You are saying I can just dig the lower portion of the footers and not frame the bottom 12"?

Correct. Only the exposed part, and maybe a couple inches below, to prevent blow outs. Place 2x4 stakes every 4 ft to keep things straight; concrete is Heavy, and that weight will want to bow the form boards out.

I need to look back at your drawing; but; how much of the slab/footer is exposed? If it's more then say, 8-12", you might need stacks and kickers, as well.

 

[LittleBittyBigJohn]

The drawing is pretty vague, it's the picture on the first post. He said the biggest thing is just to make sure there is 12" under ground. I was planning on 12"x12" footer with the 4" slab on top of that. So the footer portion should end up about 16" thick.

I have an option of a 12 or 18" clean out bucket. I don't know that I need to go 18" wide on the footer?

 

[paulsharvey]

Quick sketch. Looks like a 2x10 form board will be plently; and for that, I dont feel kickers will be required, as long as you don't use 2x2s or 1x2s as your form stakes. Also attached a generic image, that I think, explains a bit of what I mean about just forming the exposed face.

 

[paulsharvey]

The drawing is pretty vague, it's the picture on the first post. He said the biggest thing is just to make sure there is 12" under ground. I was planning on 12"x12" footer with the 4" slab on top of that. So the footer portion should end up about 16" thick.

I have an option of a 12 or 18" clean out bucket. I don't know that I need to go 18" wide on the footer?

The 12". Once that native ground or fill is over excavated, you will either have to form it, or deal with Major over runs in concrete. It's very difficult to add material back with earth forming.

 

[scootr]

The drawing is pretty vague, it's the picture on the first post. He said the biggest thing is just to make sure there is 12" under ground. I was planning on 12"x12" footer with the 4" slab on top of that. So the footer portion should end up about 16" thick.

I have an option of a 12 or 18" clean out bucket. I don't know that I need to go 18" wide on the footer?

A 12 bucket will net a 12" plus footer depending upon the soil, rock content, and operator skill. I set forms commercial and residential for 30+ yrs. Use steel stakes upright every 2ft with a wood kicker. Assume a 6" form and possible 4" under crib where needed. No need for forms underground if it's dug properly. There should be a kicker at every stake. String line your forms when kicking them.
If you have never set forms or poured concrete before hire somebody to work with you who has experience. Forms gone bad are a nightmare.

 

[paulsharvey]

Word of advice, drive your stakes down flush, or below flush with top of form board, or cut off flush, or you will be cursing while screeding the mud. Have strings set on forms, and check while mud is still not set, so you can push back in, and add stakes to anywhere that might have bowed out. You can also always throw some fill on the outside of the 2x10 form to help prevent blow outs or bowing.

 

[paulsharvey]

A 12 bucket will net a 12" plus footer depending upon the soil, rock content, and operator skill. I set forms commercial and residential for 30+ yrs. Use steel stakes upright every 2ft with a wood kicker. Assume a 6" form and possible 4" under crib where needed. There should be a kicker at every stake. String line your forms when kicking them.
If you have never set forms or poured concrete before hire somebody to work with you who has experience. Forms gone bad are a nightmare.

I had assumed a 10x20 footer, with 12" below native/fill; but I don't see a dimension, and just assumed If he only needs 3.5"-5.5" exposed, steel stakes are great, just drive them closer then 4 ft OC. that allows much cheaper 2x6 forms, or possibly even 2x4 forms. Don't cheap out and use 1x6, the cost savings are small, and you will have a slab that looks like a fat girl in a bikini...

 

[paulsharvey]

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.

Generally, saw cutting the control joints within 24-48 hours is desirable. They don't prevent cracking, they Control where the cracks happen. Depth of the cut should be about 1/4-1/3rd the thickness of the Slab (not footer); so 4" slab=1 to 1-1/4" depth of cut. 6" slab, try for 1.5-2" depth of cut. Tooled control joints look good, but don't work as well as sawed joints. Your plan shows 6x6 WWF, which I personally am a big fan of, even though the world has moved towards fiber reinforcing. As someone who has demo'd slabs, I can tell you, it's harder to break up concrete with wire, then it is concrete with fiber.

Edit: assuming that WWF is IN the concrete, not under... it has to be supported or pulled up, as the pour goes along.