Concrete form help

[Richard86]

Hey, fellas I'm pouring a pad next to my shop. My existing floor under my shop sticks out about 1 inch from under the wall. Not really enough to work a screed board on. Also I want to pour parallel to the shop. It would be a 15' x 60' pour.

The question is can I place a form close to the wall, but out far enough to run a screed on. Then immediatly after the pour pull it out and float the crete to fill the void.

I've searched the net but can't find an answer to this one. Hope I've explained well enough. I can try to post some pics if I've been to vague.


Thanks Rich

[Lew Hartswick]

I hope your not going to pour that 60 ft on one peice. Not in Nebraska. :-) The first year it'll be in several random shapes. :-)
I've seen that "screed board and remove" done if you use a 1 by
it shouldn't lower the top by enough to even see.
...lew...

[Bob Ford]

On large pours it is done all the time. Round stakes with what looks like lathe dogs 2x4 set on them. 2x4's do not have to be in concrete. After concrete is leveled stakes are pulled and holes filled.

Bob

[Richard86]

On large pours it is done all the time. Round stakes with what looks like lathe dogs 2x4 set on them. 2x4's do not have to be in concrete. After concrete is leveled stakes are pulled and holes filled.

Bob

I like that, I could actually just make, I'll call them mini-goal posts to hold the 2X4's out of rebar then after screed just pull the boards and leave the goalposts in crete. Thanks Bob

Lew, I'm not sure what you mean by one pour. But this is what I did on the shop when I built it. Three pours of 12x60. I also used keyed expansion joints every 12 foot. Thats been 10 years ago and so far so good.

[camdigger]

Or... You can set a small OD pipe (1 - 1 1/2") on bricks or scraps of cinder block to support the screed board at the grade height, and pull after screeding. A few shovel fulls of concrete in the depression made by the pipe touched up with a bull float, and noone the wiser on how you did it.

Air entrainment, fibre reenforcement, and lots of rebar (3/8" rebar on 18" centers) will help prevent cracking, but there are no guarantees. FWIW wire 6" square wire mesh is a good substitute for rebar, and there'll be less tying. My garage floor is 25' x 39' continuous slab. After 10 years, it is still crack free. Oh, the garage isn't heated either, temperatures run from + 28C to -40C in my garage. I'm a bit further North than Nebraska....

[shoprat]

i used to pour and finish concrete i always used 1 1/2od gavinised pipe
8-10 ft long and then use 1x3 wood stakes pounded in about 6 ft apart.
set your pipe on top and pound in 2 nails like a vee to cradle the pipe
then you set your grade with level on the pipe and work your way down
to the end form.

when you are ready to pour you just screed down to the length of pipe
slide the pipe down to the next set of stakes and so on.you can pound the stakes in throw some mud in the spot where the pipe was and keep on going
hope this helps and also concrete work is what 18 year olds were put on this for !!

[darryl]

Sounds like it will be under control. I'm wondering what method, if any, will be used to key the new pad to the old. Do you drill, then mortar in pieces of rebar, or is it something to worry about at all?

[recoilless]

Darryl, it sounds like he is just pouring a slab in which case there would be no reason to dowel into existing. I'd just run a strip of expansion joint between the two and leave it at that.

[Richard86]

This is actually going to be a 30ft.x60ft. addition to the shop. When I originally built my shop I made my own forms out of 12ft. long flat metal with a rib formed in the middle. They are 5 inches tall. This makes for a tongue and groove joint between the pours. These forms are one of the handiest things I've ever made, reusable and very easy to set up.

So the edge of my shop floor has the female part of the t&g. This should tie the edges together. I appreciate all the input, I'm now thinking I'll use the goal posts with 1.5 pipe.

Later Rich

[Peter.]

I've seen concrete gangs using tubing suspended on tripod stools made from three L-shared rebars. The short leg of the L's (about 6") are welded together in a triangle making a tripod with a triangle hole in the top. A length of dywidag bar is dropped from the middle of the tripod with the end bent as a hook to carry a scaffold tube. Several are used to suspend the tube and make it level and the pour is levelled from this. When the pour is in pull out the stools and float the surface.