concrete floor questions

[J Persons]

While talking to a contractor about my proposed shop, he stated that they use 5000psi concrete for the floor, at 4" thick, and 5" where the lift will be. And if I wanted any rebar and/or mesh that I would have to provide it and he would install it at the time of the pour. He stated that he also uses the fiber concrete. This is a pole building.

Question is, what size of rebar and steel mesh should I provide? The slab will be 30X50 under roof with a 12X50 lean to type porch on the back of the building.
Thanks in advance, John

 

[Edger]

While talking to a contractor about my proposed shop, he stated that they use 5000psi concrete for the floor, at 4" thick, and 5" where the lift will be. And if I wanted any rebar and/or mesh that I would have to provide it and he would install it at the time of the pour. He stated that he also uses the fiber concrete. This is a pole building.

Question is, what size of rebar and steel mesh should I provide? The slab will be 30X50 under roof with a 12X50 lean to type porch on the back of the building.
Thanks in advance, John

I always worry when a contractor cannot supply all the goods for the job. I would advise you to get other quotes. The biggest con men always tell people that they only supply the best methods and materials which is often true except that they cannot install it properly and mess the whole thing up. Another trait of con men is that they never own proper equipment, trucks, staff etc. so they find supplying everything needed to be more difficult. If he wants you to supply the mesh I would be wary.

 

[383]

It takes a while to install, what does he mean by "at the time of the pour"? I installed 1/2'' re-bar in a two foot grid.

 

[ConCretin]

383's picture shows a nice installation though I might have placed my supports a bit closer together.

Wire mesh is really all you need. Get a W6x6/2.9x2.9 wire in sheets, not rolls. Make sure it is well supported. Don't trust the finishing crew to pull it up as they go - it doesn't work and they'll lay waste to your vapor barrier.

Fiber mesh and wire mesh make a good combo but 5000 psi is overkill for a slab.

 

[the king crew]

Mine was 3/8" rebar 24" apart. It took my contractor the better part of an afternoon to cut and tie it togther. My contractor supplied everything that went into and under the slab. The blueprint called for a 3000 psi miix.
Lee

 

[buening]

I too would be leary of a contractor that cannot supply the reinforcement. He should also have enough experience to guide you on what to use in your situation (rebar and/or fibers).

Wire mesh (also called welded wire fabric/WWF) in sheets allows for quicker installation, but keep in mind it is beneficial if the wire spacing is large enough so that a shoe can go through. Granted a concrete worker will still step on the wire, but if you can space it far enough that they can stand in between the wires it will prevent it from getting all bent up. I tend to prefer #3 (3/8") rebar at 24" centers which is a bit overkill, and if you don't mind the time with all the rebar tying and stands/chairs. The rebar isn't intended for additional strength, but rather to minimize the shrinkage cracking of common unreinforced slabs. My experience is in industrial floors and not garage floors, so take this with a grain of salt.

There are a million different thoughts out there on slabs, from only using mesh fibers, using both rebar and mesh fibers, using WWF and mesh fibers, etc. While specifying 5000psi is overkill, your standard 5bag (3500 or 4000psi) mix will likely test that high at the 27day test anyways from my experience.

 

[Falcon67]

I went close to code specs - two 1/2" bars in the footings and a grid of 3/8" on 18" centers. The concrete was speced at 3500 minimum, concrete guy said the mix should top out at near 5000 anyway. I went 4" more or less, 12x12 footings with three beams across and one down the middle. 24x40.

"at time of pour" - WFT, no way. Took my guys two full afternoons to get it all bent, cut, suspended and tied. Plus I called for inspection.

 

[buening]

Spot on Falcon

 

[J Persons]

I've decided not to go with the contractor mentioned in my original post, there were just too many things that didn't seem right and I couldn't find anyone that he has done business with. He also said he would e mail me a copy of the quote and a plan, and as of today nothing has shown up. I think my best bet is to contact Muller buildings and proceed from there. They have a facilities in Southern Louisiana and East Texas, and will be much easier to deal with.
Thanks to all those that responded,
John

 

[Edger]

Well done, good decision, always hard when you have to do that.

 

[joes169]

If you're in Texas or La., 5000 psi for an interior floor is WAY overkill, and is probably a good indicator that the contractor is in over his head. Good choice in moving on from him.

As for reinforcement, don't buy into the fibermesh alone, it's nothing more than "snake oil". 6x6x10 guage WWM or #3 rebar on 3' or less centers each way will perform much better over time. If it's relatively humid where you are, I wouldn't think twice about adding a vapor barrier under the floor as well.

 

[macdabs]

Many contractors want the customer to supply the rebar now do the constant changing steel prices.. I have seen #4 and #7 rebar in 20 ft lengths with 350 pieces per order change 2-$5.00 per stick in less than 2 days.

With the high cost of concrete and steel I recommend #4 on 12'' centers,4000 psi 5-6" thick. And look at the guys past work first.A good concrete guy is like a top notch auto painter, never out of work and get a preium for his work.

Mac