Need Help Framing a Turn-Down-Slab

[LittleBittyBigJohn]

If I'm understanding correctly I'm just driving in 2x4 stakes on the outside of the form. If that's the case is there any worry about the footer blowing out as thin as the dirt will be?

 

[paulsharvey]

Also, I dont know if You are pouring, or hiring that out, But, it's better to pour a bit drier (lower slump) and work a bit harder on the pour, than pour wetter (high slump), have an easier pour, and longer finish time, as well as lower final strength. A 5" slump is 100% workable, maybe 6" with the footers and bars, but don't let anyone tell you it has too be an 8" or higher slump. Seen plenty of guys that order a 6", and immediately, without even seeing g the mud, flash the driver, add 20 gallons...

 

[LittleBittyBigJohn]

I'm hiring out the pour and finish. I have a group lined up for $1,500

 

[paulsharvey]

If I'm understanding correctly I'm just driving in 2x4 stakes on the outside of the form. If that's the case is there any worry about the footer blowing out as thin as the dirt will be?

View attachment 816031

Not really, but if it is an issue, add a kicker, or a 2nd stake back a couple feet, and a board from rear stack to front stack, angled. Also, steel stakes are easier to drive and it would be less issue. The round style are 5/8" diameter, a out 16-24" long, there is also a flat style, that's about 3/8" thick x about 2" wide. Both styles drive Way and pull way easier then 2x4s, and have pre-drilled holes for your duplex nails. Not overly expensive, but a couple dollars each will add up, if you never need them again.

 

[paulsharvey]

Seems steel stakes have gone up too... But really, $3.60 per stake isn't that much more then buying 8 ft 2x4s to cut up into stakes. And you can drive them with a framing hammer. That's not going to happen with 2x4 stake, that's 8 lbs sledge time if you want to drive them very deep. They dont hold equal to a 2x4, hence the 24" vs 48" spacing.

 

[LittleBittyBigJohn]

I went by the lumber yard in the way home from work. They said to form first then dig the footers. Said if i dig footers first the stakes will blow out. Does that make sense?

It sounds good but I'll have to be creative with the machine to get it straddled over the forms.

Also they said use a rebar chair for the lower 2 rebar runs. Then another chair on top of that run for the top 2.

 

[paulsharvey]

I went by the lumber yard in the way home from work. They said to form first then dig the footers. Said if i dig footers first the stakes will blow out. Does that make sense?

It sounds good but I'll have to be creative with the machine to get it straddled over the forms.

Also they said use a rebar chair for the lower 2 rebar runs. Then another chair on top of that run for the top 2.

Yes. You will have to 'clean' the sides up with a flat shovel after digging with the machine, unless you are just plain a stud hoe operator.

As for the dual chairs, I guess that would work, but you will definitely need to wire tie the top chair to the bottom bars, or it will fall off, especially when you start pouring.

Do you plan to be onsite when they pour? I would definitely try, and I know it might be uncomfortable, but don't be shy telling them to pick up the wire, if it's not supported well with wire chairs or wired to bricks. The chairs are like $0.60 each, in packs of 100, and they really do help keep the wire off the ground. Wire under the concrete does nothing, but does wonders when it's in the center. Engineers will tell you it just prevents cracks during curing, but it does more than that...

For the machine, you can rotate the cab, then off set the hoe, and dig more or less straight. See below video, around 4m33s, if you aren't familiar with what I mean.

View attachment 816093

 

[LittleBittyBigJohn]

I had a couple of fails yesterday after work. I started laying out my corners using 18" rebar as the corner pins. The ends of my tapes are too small to go around the rebar. I got one wedged on there good enough to hold and ended up tearing off the tip. Then I decided to go ahead and start my batter boards. I cut a 2X4 at an angle and started pounding. Started with my 4lb shop hammer then went to my 12 pound sledge. I didn't get it but 6-8" in the ground. There is no way I'm going to be able to drive them farther than that.

Couple questions, I don't want to buy the metal stakes if I can help it, they are expensive. How far do I need to get the 2X4 stakes in the ground around my forms. I assume I need them pretty deep since the dirt will be so thin once I dig the footer in front of them. Also, I can probably get them deeper if I rip them in half, making them 2X2, will that be ok?

I tend to overthink everything but this is a big expense and I have literally zero experience with this.

 

[paulsharvey]

You want your form board to be able to withstand the force of the concrete weight pushing out. That's going to be in the neighborhood of 50 lbs per linear foot I'm guessing, depending on wet it is, ect. Your soil conditions really determine how much you need to stake. Ripping 2x4s, to 2x2s might work, and is common practice on sidewalks/driveway pours, where you are holding back 4 or 6" of concrete. You can always throw fill on the outside of the form boards to provide backing support. I can't really advice beyond that, other than, the time to add stakes is Before a blow out/bow.

Edit: don't know if most people can picture how heavy a Cubic Yard of concrete is; think of 42-80# of quickcrey, Plus water, and that's a single yard. Now, you aren't supporting nearly that, but you are fighting some real weight wanting to push out. Also, does a 1" bow out in a 40 ft wall cause you great concern? Maybe, Maybe not; but a 3 or 4" Bow might. Depends on what/how you are building on top of the Slab, as well as your personal level of acceptance. You don't want to know how out of square/level/straight many new construction homes are.

 

[ning]

Buy the metal stakes, they'll last forever and you'll find things to use them for all over the place in landscaping or other construction.

 

[Omega Woods]

Not an expert at this by any means but this guy is.

 

[Chewwy]

As previously described, the guy who built our forms use 2x2s for the forms for a 5 1/2 inch thick pad and they were placed about every 4 ft. Our soil is mostly red clay that is slippery that owl s _ _ t when wet and hard as bricks when dry.

If you are unsure you could use 2x2s every two feet.

But considering everything, the metal stakes might be the best option and are unlikely to cost that much relative to the cost of the concrete, forms, rebar, wire mesh, and labor.

They will certainly be much easier to drive in the ground

 

[MossRoad]

Not an expert at this by any means but this guy is.

He said something about lifting the wire, but I never saw them lifting the wire, and they were finishing it and the wire still appeared to be flat on the plastic. I think it's about useless if it's at the bottom of the slab VS embedded in the center of the slab.

I'd have preferred to see them put it up on chairs so it stayed suspended in the concrete.

If I missed something, ignore the comments. I just didn't see it.

 

[MossRoad]

...

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.

You could make some u-shaped pieces of rebar to look like giant staples, then push them into the dirt to the depth you want the upper run of rebar to be. Then tie the horizontal runs of rebar to each side of them at the desired heights.

Rebar is cheap and you can bend u-shapes with your knee and hands pretty quick. Or use a rebar bender, as they are cheap as well.

 

[LittleBittyBigJohn]

Ordered the materials. Not as bad as I was expecting. $1,360

15 pcs - 2x4x20
40 pcs - 1/2x20 rebar
120 pcs - 3" dual rebar chairs
1,000 pcs - Rebar ties
2 pcs - rebar wire twister
1 roll - 6 mil 20x100 plastic
12 pcs - 6x6 welded wire 8'x20'

 

[paulsharvey]

Might want to grab a bag or 3 of wire chairs.

 

[Mike1955]

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

He may have a dozer in there. Not an overkill then

 

[scootr]

He may have a dozer in there. Not an overkill then

My remark was based upon 30 yrs of Residential, Commercial, and Govt specified concrete work.
But you are right, he might put an M1A1 tank in there ... maybe it should be more excessive?

 

[paulsharvey]

The stirrups or hoops were suggested more as an easy/cheap way to keep the 4-#4s in place. Not being an engineer, I can't say how much difference there is between 2-#5s vs 4-#4s in tension/shear, but around here, that slab would typically just have 2-#5s. The hoops/stirrups where not suggested to add strength, just for ease of installation.

Edit: 0.20 square inches per #4 vs 0.31 square inches per #5; so yes, 4-#4s are 0.80 square inches vs 0.62 sq inches; so the quad 4s are significantly stronger then dual 5s.

 

[LittleBittyBigJohn]

He may have a dozer in there. Not an overkill then

Dozer is borrowed it won't go in there. But I do like the tank idea....