Grading a pad

Discussion in 'Heavy Equipment & Pavement' started by queen of spades, Mar 12, 2010.

  1. AWJ Services

    AWJ Services LawnSite Platinum Member
    from Ga
    Posts: 4,276

    Our soil here may be different than where your from. Gravel under a slab helps but it is not a must. We also do not have freezing issues here since our frost line rarely gets more than a few inches deep.
     
  2. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    Rebar is cheap insurance if your in doubt put a good grid of 1/2 rebar and get a high strength mix of concrete. The worst thing you want to happen is a crack and there is never any gaurantees of getting the ground perfectly compacted.

    A 32x24 is a decent sized slab I would get professional placers to do the job.
     
  3. queen of spades

    queen of spades LawnSite Member
    Posts: 217

    GR: what should I expect to pay for enough rebar for a 32x24 pad?
     
  4. ksss

    ksss LawnSite Fanatic
    Posts: 7,128


    You might also check with your concrete provider and price fiber mesh. I think its very effective, cheaper both in material and labor (its already mixed in the concrete so you do nothing). Might be something to look into.
     
  5. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    Prices are different everywhere its been awhile since I have had to buy any rebar.

    If you want the slab really strong then a 1 foot grid with 1/2 inch bar you wouldn't have any problems. You could go with a 2 foot grid that would give you a decent strength. Buy the pre looped tie wires and a spinner to twist the bailing wire.

    If you had good stable ground you could get away with that light wire mesh but I prefer rebar. If you don't want to use 1/2 inch use 3/8s rebar it is a little cheaper.

    Do you want to chance the slab cracking then you have to redo a section or the whole thing.

    Third option is this slab going to be power troweled to give a smooth finish if not you can use the wire mesh and have the redi mix company put the kitti hair into the mix which is the fiberglass strands. That will give you a strong slab without all the rebar BUT you can't power trowel fiberglass reienforced concrete you get the fuzzies.

    Any which way you choose you can never have enough reinforcing in concrete.
     
  6. AWJ Services

    AWJ Services LawnSite Platinum Member
    from Ga
    Posts: 4,276

    I have mixed feelings about fiber. I actually refuse to use it. It only adds about 250 psi strength yet adds about 10 dollars a yard here. Each step up in strength here adds 500 psi and costs 5 dollars per upgrade.
     
  7. Danny Boy

    Danny Boy LawnSite Senior Member
    Posts: 255

    Up here 5/8 rebar 20 foot long is about 8 bucks a length and for a 16 x 16 inch grid at these prices a budget of 500 for the material would likely do, plus your labour to install it, I would not do a slab without it, and also put a layer of 6 mil poly under it too to keep the damp down and prolong the life of the concrete....
     
  8. ksss

    ksss LawnSite Fanatic
    Posts: 7,128


    Its increases in psi are not as great but its ability resist cracking and peeling are much better. If you have ever had to remove fiber reinforced concrete the difference between fiber and non or even fiber and rebar is significant. You can power trowel fiber concrete. The hairs shed themselves.
     
  9. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    I'am not sure if I would use 5/8s in a 4 inch thick slab I assume this is a 4 inch slab ?

    In a 8-10 inch foundation wall I would use 5/8s.

    For myself we don't have red clay or pour concrete or work over clay. For a slab for a shop some guys are using 2 inch sytrofoam SM under the slab for a thermal break.

    It all depends on the areas and you should do what ever is recommended for your area but universally you always want a good bed of rebar in your concrete.

    The only reason why I wouldn't use 5/8s in a 4 inch slab it is too rigid. When your placing your slab no you don't pour concrete you want the rebar in the middle of the slab thickness. Using 2x4s you don't get a full "4" inch thick slab is its 3 1/2.

    For your case if you want a thicker slab you can form it up with 1x6 that you rip on a table saw to 4 inches.

    So you will have 9.5 yards of concrete approx not sure what concrete costs in your area but that would be about 1000 dollars for a a person like me. In B.C. we have trucks that will deliver that in one load I assume in the USA it is the same.
     
  10. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    The concrete placers here don't recommend power troweling fiberglass entrained concrete. These guys do some large slabs ie supermarket size slabs.

    You want to make somebodies day throw some brown sugar on their slab :laugh:
     

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