Flat Concrete Floor, How to

[BuickFarmer]

I see lots of concrete slabs being poured on here. I seldom see any hub stakes set that can be used for screeding or any other means to ensure the floor comes out flat. I know some concrete finishers probably just have a "good eye" for ensuring it is flat/level but do I really want to count on that. I am not planning on any floor drains and am not sloping the floor to the door or anything, I just want the floor nice and flat and level. Talking about a 40x36 foot slab in a pole barn here. Thoughts?

 

[dieselgarage]

The guys that did mine used a laser level. They would smooth out a a few spots at grade then just hand screeded it from those spots. I did not want any rods or re-bar pounded through my vapor barrier. One guy I had quote it wanted to put in 40 bars.

 

[T-Mac]

what i did-set the screed pipes up with a laser level

 

[JimVonBaden]

I've never seen it done with screed pipes. How do you get them out and the divots filled once screeding is done?

Jim

 

[T-Mac]

yanked them out and filled divots by throwing concrete into divots and bull floating-i just had 3/8 rebar welded to pipes driven far enough into ground to support screed

 

[Big Bad Dad]

The conc guys I used to use would cut a "story sticK' to length and guage down from the ceiling joists overhead. (Of course, this only applies if you have a level ceiling framed up prior to pouring the concrete.)

 

[ilovevocs]

If your that particular it may be worth looking for a contractor with a laser screed.

 

[T-Mac]

laser screeds are the sh*t

 

[Jere]

A water level will do the trick also

 

[spotco2]

Don't use the guy that did this one for me

http://www.garagejournal.com/forum/showthread.php?t=209193

 

[Justanoldguy]

Lasers are used big time.
A good team can get it pretty accurate without any hassle.

 

[BuickFarmer]

Thanks everyone for your input. Spotco2, man what an ordeal that must have been. The crew I plan on using are guys that use to work for me pouring driveways and sidewalks and other flat work, so definitely won't be those imbeciles you had to deal with. They know me, I taught them well, so am sure they will give it their best. My plan right now is to drive #4 rebar stakes in, in a 11 ft grid pattern so they can wet screed to them, then drive the rebar on into the ground after establishing that grade. The pins will indeed be driven through the vapor barrier but since they will be left in I think the negative impact will be negligible. The filled subgrade is high and dry, is of a sandy clay and at 100+% compaction.

 

[davo727]

Im buying a 20 foot aluminum screed and doing my slab in sections 16 feet wide, one at a time. That ought to make it flat

 

[Hornman]

Im buying a 20 foot aluminum screed and doing my slab in sections 16 feet wide, one at a time. That ought to make it flat

Are you using the tubular rotating aluminum screed they use on the concrete roads in the Houston area?

 

[davo727]

No, just a 2 in x 5 in rectangular aluminum tubing, 20 ft

Are you using the tubular rotating aluminum screed they use on the concrete roads in the Houston area?

 

[NUTTSGT]

We used a laser level on mine, it helps to have family members that work in construction.



You can see the pole with the detector standing in the corner by the breaker box. Attached to the beam,above the wheel barrows is the laser itself. We poured the back corner (out of the picture) bringing out halfway and to the front. Once that was done, we went to the back wall and finished out to the front again. The floor is flat without any drains or taper, other that at the doors.

 

[ConCretin]

Keep in mind that a achieving a flat floor goes well beyond the method used to establish grade and screed the concrete. Most important is skill and experience of the finishers.

The screeding process determines the overall levelness of the floor. Subsequent finishing operations determine the localized waviness of the surface.

Most crews up here use the wet screed method. They use a laser level to build pads of concrete at the desired grade. They use the pads to screed a level strip of concrete in between. They turn 90 degrees and use the level strips on both ends to guide the screed.

For really level floors, a walk behind or machine mounted laser guided screed works wonders. We rarely use pipe screeds and never poke holes in our vapor barriers with rebar (amateur hour)

Screeding is harder than it looks and requires good rakers to maintain the proper amount of concrete in front. Next you bull float, which seals the surface, brings up the cream and further levels the surface. On super-flat floors, a bump cutter is used to knock down high spots and fill low spots. Finally you float the floor, which is typically done with a power trowel. Floating basically levels the layer of concrete paste on the surface. Pans work best for a really flat floor. After this you're basically just shining things up.

All the aforementioned steps require exact timing and vary greatly with weather conditions. Getting a really flat floor is an art. If you want one, ya gotta find the right guys. Definitely not a DIY operation.

Wow, that was longer than I thought. Sorry

 

[racedaymechanic]

Keep in mind that a achieving a flat floor goes well beyond the method used to establish grade and screed the concrete. Most important is skill and experience of the finishers.

The screeding process determines the overall levelness of the floor. Subsequent finishing operations determine the localized waviness of the surface.

Most crews up here use the wet screed method. They use a laser level to build pads of concrete at the desired grade. They use the pads to screed a level strip of concrete in between. They turn 90 degrees and use the level strips on both ends to guide the screed.

For really level floors, a walk behind or machine mounted laser guided screed works wonders. We rarely use pipe screeds and never poke holes in our vapor barriers with rebar (amateur hour)

Screeding is harder than it looks and requires good rakers to maintain the proper amount of concrete in front. Next you bull float, which seals the surface, brings up the cream and further levels the surface. On super-flat floors, a bump cutter is used to knock down high spots and fill low spots. Finally you float the floor, which is typically done with a power trowel. Floating basically levels the layer of concrete paste on the surface. Pans work best for a really flat floor. After this your basically just shining things up.

All the aforementioned steps require exact timing and vary greatly with weather conditions. Getting a really flat floor is an art. If you want one, ya gotta find the right guys. Definitely not a DIY operation.

Wow, that was longer than I thought. Sorry

I worked construction for 30 years and had a hand in a lot of concrete pours,
Im getting too old for that now so when I needed my floor in my 30x30 shop pour I hired it done, I kid you not it is the flattest floor I have ever seen, they poured it pretty stiff, used a long aluminum rectangle screed and a laser to screed it, no pipes or anything thru the vapor barrier, power troweled then hand trowel, absolutely pool table flat I couldn't be happier

 

[RMW1]

Thanks everyone for your input. Spotco2, man what an ordeal that must have been. The crew I plan on using are guys that use to work for me pouring driveways and sidewalks and other flat work, so definitely won't be those imbeciles you had to deal with. They know me, I taught them well, so am sure they will give it their best. My plan right now is to drive #4 rebar stakes in, in a 11 ft grid pattern so they can wet screed to them, then drive the rebar on into the ground after establishing that grade. The pins will indeed be driven through the vapor barrier but since they will be left in I think the negative impact will be negligible. The filled subgrade is high and dry, is of a sandy clay and at 100+% compaction.

I realize this is a very old thread, but here is a suggestion for future jobs that do not puncture the vapor barrier:
Use a chair like this one linked below to support the rebar grid at locations close enough to the perimeter form so that the screed can reach across these reference points. The top of the chair is flat so you can easily place a temporary spacer of appropriate height on top of it. Place the spacer after the concrete is poured in because the pouring will dislodge the spacer. After screeding, pluck out the spacer and fill the void with a handful of mud and trowel it flat.

https://www.lowes.com/pd/PROWORX-4-33-in-x-2-83-in-Polypropylene-Rebar-Chair/4070207