We are a week and a half away from this, but I want to be prepared. It is a slab on compacted fill, radiant heat tubing tied to the mesh, and we will pour it atop a layer of 2″ rigid foam insulation. We are using sheet mesh rather than rolled mesh, so we don’t have to deal with “roll set” in the mesh.
At pour time, what would you do to insure the slab top is as level and dip-free as possible?
One other question: what would you do to get the mesh and heat-tubing array elevated more toward the center of the 4″ slab?
Replies
Talk to the finisher in advance, and ask him about using "pans" on his machine. I am not sure if you can use them on a "walk-behind" machine, but I know that on a dual-rotor "rider" a set of pans and a good operator can get it flat within thousandths of an inch. That is how it's done on huge slabs such as automated warehouses. You may not have anyone with that expertise in your area, or be able to afford them, but it is possible.
Try this link to see what I'm talking about: http://www.alleneng.com/
To find a contractor in your area that can do this kind of work (if it's what you really want), give Allen Engineering a call and they'll get the name of someone in your area.
Edited 6/7/2003 8:29:40 PM ET by RUSTYCAS
To elevate your mesh, you would be looking for "chairs" or "jacks", now finding those, is phone calls to lumber yard, masonry supply , or a rental yard, I know ya won't be returning those things, but give them a call anyway. Note: I have always been told- you want your rebar/mesh in the bottom 1/2, or ideally 1/3 up from bottom. You want your slab flat, well, you either have to trust your General Contractor to have quality subs,, or call the Redi-mix company (s) and try and talk with the person who schedules the concrete, get some references. Oh, one last note my concrete finisher, well, he likes all unfamiliar people with the concrete trade to take at least two valiums, prior to pour, if they are on site. Good Luck Jim J, don't forget to have Plenty of help "good/experienced" people at time of pour, and I'll take care of the weather, and you make certain you have water on site.
Way back when I started. We used to pour motel slabs. The guy I used to work for was absolutely nuts about the pours. They had to be flat. The day before the pour we would run around setting the screed pipe supports. The supports were simply 2X stakes set with a transit with a couple of nails driven into the top to hold a piece of pipe.
All of these slabs were poured in 10' swaths with one edge of the screed always resting on a 2" pipe.
After a rain you could walk across a 300 X 60 ft slab in a pair of sneakers and not get your feet wet.
Turtleneck
the only miracles I've ever produced are waiting for me at home
We use a laser on the concrete rakes to insure it is level. Also a motor screed. The mesh amd radiant heating tubes should be in the bottem 1/3. Nothing fancy just rase the mesh while they are placing the concrete with your hands and/or rakes.
Tim Kiser
This is a new sub I am working with, and I am sure he does not have a motor screed. He does have a good laser level, though. The foam insulation under the slab sort of complicates things. Doesn't permit us to hammer in pegs on which to mount screed pipes or anything (I think.)
This is low tech, and strictly residential, but I don't want high spots or puddles. Any advice?
Laser level secured to the handle of the rake, a good straight edge and a competent finisher will get you a good job. If for some reason this does not work you can get concrete sander to smooth out the floor.
tim
Describe in a little more detail, please. We have a laser level, and its target/receiver is mean to screw-clamp to a level stick. By "rake," what do you mean? Is it something different from a bull float? Where on the rake's handle do you fasten the laser target?
Clamp the target/reciever to the a pipe or stick on the screed. Set the laser on the foundation wall or some blocks a little ouside of the pour. Works pretty well with rotoray laser levels and some good men on the screed. You need a good man on the bull float too. The best of them can "feel" the highs and lows in a slab and drag out the highs, and call for a shovel full here and there for the lows.
If you don't have a rotary level, rent one for the pour. Just be carefull the concrete truck doesn't run over it. Something about expensive levels and concrete trucks seem to attract each other
Dave.
http://www.concretenetwork.com/concrete/slabs/highquality.htm
I just found this site check it out. A come-along (a tool that looks like a hoe and has a long straight edged blade) it what I cakk a concrete rake.
tim
I gotta ask: Why do you NEED this floor to be "perfect"?
It is "your money" but some times you need to look at the diminishing returns of getting increased accuracy on any particular task.
Getting it within a 1/4" will be nominal.
an 1/8" will cost a bit more.
A 1/16th will cost alot more.
And a 1/1000" will probably be prohibitive unless you are planning on doing laser eye surgery in your basement.
JMNSHO
Mr T
Do not try this at home!
I am an Experienced Professional!
I didn't say "perfect." I am just looking for some good advice on the techniques concrete guys use to get a level and flat slab. I am getting some good tips here.
In my neck of the woods, very little housing gets its main floor on a slab, and this spec I am building has that feature, with a white oak wood floor over it. My 'crete sub is used to doing basement floor and garage floor pours, and I just want a heads up so I can work to achieve a good flat base.
He has a power screed and a good laser, and says he will pole it in to dial the level right. I want to see that he cuts the bumps and fills in the puddle holes as much as he can. I may buy him a good tamper rake, and outfit the handle on it so it will work with his laser receiver target.
My brother owns a commercial GC outfit that does WalMarts and Targets, among other things, and he has told me all about how the big flatwork specialists do those floors to the Fn numbers demanded by the big guys. I am not looking for that, just some advice so I can assist my guy in doing a good job on this 1200 sf pour.
OK Mr T
Do not try this at home!
I am an Experienced Professional!