Any Tips On Forming A Monolithic Slab

72chevy4x4

In my area, a monothic slab is 24" deep, 12" wide around the perimeter with the standard 4" slab with 2 bars in the trench. I'm not a concrete guy but have done a number of slabs, but not had a problem with the depth at the edges as they haven't been monolithic slabs. My stakes aren't keeping the forms up b/c of the 2' trench (the moist soil isn't helping), suppose if they were deeper it wouldn't be a problem. I am using 2x4 stakes with 2x12's for my exterior forms screwed (less impact to disturb soil) or nailed together. I pulled my lines and everything was level and straight-come back the following day to lay the rebar and notice some of the forms have settled.

Can you provide any tips for keeping my forms and straight?

neolitic

Kickers.
2X4 braces from the top of the form with a stake to hold it.

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Vabuilder

YEAH, and alot of them too !!!

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cleveman

Kickers are fine if you aren't too high with your forms and you don't wait too long before you pour.

If you want something which will hold up for some time or your forms are high, then build some brackets out of 2x4's. These are a triangle on a longer 2x4. Let's say the top of your forms are 18" above grade. Screw an 18" 2x4 on the end of a 3' 2x4 at a right angle. Then come down at a 45 degree angle from the 18" piece with another piece, screwing everything together.

Drill two 5/8" holes in each 3' piece. One hole can be under the triangle. Fix these to the ground with round stakes. As the stakes are taking hold, slip a nail in a hole close to the 2x4 and give the stake a few more whacks, bending and driving the nail into the wood a bit.

Now screw your 2x12's to these brackets (from the outside of course). These are easy to disassemble and can be used time and time again and will hold up for a long time before the pour and most importantly during the pour.

ConstSvcs

I second that........

Primax

I am a firm believer in tie wire, along with the usual overkill on the pegs and bracing, I safeguard with a length of doubled tie wire secured to the top mesh and either through the form or around the dropper. I use this method to secure 6-800 shutters. Just make sure that you load the mesh up with bulk concrete before pouring the edge beam, the mesh won't move latterally once covered, very strong anchor.

billy d

Hi guys took me some time to get my head round the term MONOLITHIC SLAB(Thick brit,2nations separated by a common language)Sounds like some thing out of a spielberg movie.Checked some back posts and I think I`ve got it now your talking about a slab and foundation in 1 pour. When your shutter is dropping and falling try this,drive a 4*1 peg deep next to the shutter OK, when the ground is to soft to hold a peg for a raked shore try dropping a 4*3 on the soil drive a peg behind it about a foot from both ends and one in the middle drive a peg in front of these on the other side of the 4*3.Get some HD wire about 1 /8" thick and form a figure of 8 on each opposing peg use a set of knips or a screw driver to twist the wire in the middle like a spanish windless so the pegs front and back pull on each other and close on the4*3.this will also work in stony ground as well but you must use ree bar instead of pegs.Lets call the 4*3 position 1 ,nail a 4*1 from the sole of the shutter to position 1 and one from the head of the shutter to position 1, checking for plumb and straight all the time.Lay a 4*3 off cut next to the peg you drove by the shutter and nail them together the 4*3 will stop the peg from dropping and you can nail the peg to the shutter, use shuttering nails they have a double head so you can drive them home and you`ve still got a head on the nail to pull when you strike your shutters.Don`t forget to use a whaling a cross the shutter joints. So lets take this a stage further if it`s not your job try talk to the architect or JC to increase the measurements for the foundation 4" in length .O.A.8" and then nail a4*3 on the inside of the shutter level with the finished hight of the slab so what you`ve now done is create a ledge 3" lower than the cold joint on the slab.This ledge can now be used for your drainage pipe a round the building as we know water will always find it`s own level so the water is always 3" lower than the cold joint.Plus there is no problems with levels if you build in concrete leave the 4*3 where it is and you have a perfect platform for your shutters ,if you build in block it will catch all the spills from the morter and save the job of scratching it of the concrete.Hope this helps any one.

sawyerEd

Dear 72 chev4x4,
yikes, you've got a serious problem. if your forms won't stay put overnight, what does that tell you about the load bearing capacity of the soil? you may be working over a layer of something that will not hold up the structure you are building. Be careful and get some professional advice.

Hoven

I agree with Sawyer get a soil test to cover your A$$. Not seeing the job makes it tough but I usually use 4foot metal stakes for jobs like this. They have holes pre-drilled in them to accept a 16 penny duplex nail. I would also space them about every 3 feet with 2x4 kicker braces to smaller stake in between . I also have screw braces that are made of steel that you attach a 2x4 to and it has a hole in the foot of the brace to accept a metal stake. These are nice because if the forms do move because of the crete weight against it its just claw hammer to tune the brace in or out. Plus no cutting a forest of wooden stakes. The metal will last forever. The thing is the fact that your going from 2ft thick 12inch wide perimeter to a 4 in slab. Perimeter weight issues might cause cracking to be severe down the road. I would beef up the floor area to 5.5 to 6 in thick or haunch the perimeter at a 45 deg angle or less so the pour gets thicker as you make it to the actual floor. Reinforcement is the key.