Replies

1. 
   brownbagg | Apr 27, 2008 07:32pm | #1

   vapor barrier is 100% necassary, it will keep the soil moistue from migration into your slab and also keep the concrete from drying too quick causing cracking. If moistue migrated into the dlab you can never paint the slab because the paint wont stick. beside vapor barier are cheap insurance
1. 
   john7g | Apr 27, 2008 08:28pm | #2

   used to work in a small hangar complex. both hangars side by side.  1 floor would sweat incessantly in the spring and be like a skating rink until the moisture balanced out.  Only thing I could figure is that the palstic was left out on that slab. 

2. 
   CaptainMayhem | Apr 27, 2008 09:43pm | #3

   Not to sound arrogant(because I'm rather young and naive) however, if you don't put vb down below your slab(and foam board for that matter, you might as well not pour at all. As far as the rebar goes, on a standard 12 inches on center, closer for more dead load. I mean come on, 5 bar is dirty cheap and for the added strength compared to the few dollars extra, youy really can't go wrong....

   p.s. DEFINITELY use vapor barrier

   good luck either way

   All I ever wanted in life was an unfair advantage...

3. 
   KenHill3 | Apr 27, 2008 10:06pm | #4

   5" for heavy equipment?

1. 
   IMERC | Apr 27, 2008 11:40pm | #5

   doesn't sound like enough does it??? 

   Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

   WOW!!! What a Ride!Forget the primal scream, just ROAR!!!

1. 
   KenHill3 | Apr 28, 2008 12:00am | #6

   Doesn't SOUND like it, but I'm neither an engineer or a concrete guy.

4. 
   davidmeiland | Apr 28, 2008 12:08am | #7

   It is very simple for an engineer to spec a slab like this. The guy I call has slab design software on his desktop and can punch in a few parameters and give me thickness, reinforcement, mix design, etc., over the phone. I am guessing you want 6 inches, 3000 PSI, #5 @ 12" OCEW placed low in the slab, control joints placed 10' apart or less, and of course your subgrade should be immaculate.

1. 
   brownbagg | Apr 28, 2008 01:42am | #9

   I am guessing you want 6 inches, 3000 PSI, #5 @ 12" OCEW placed low in the slab, control joints placed 10' apart or less, and of course your subgrade should be immaculate.i would go everything but 4000 psi with no more then 5 slump

1. 
   davidmeiland | Apr 28, 2008 04:14am | #10

   PSI.... let's talk sacks.... would your 4000 be 6-sack?

   Around here it seems guys say 3000 = 6-sack. Last time I had to have a crush test it was 6-sack and the 28 day test was 4300 or something like that.

1. 
   brownbagg | Apr 28, 2008 05:33am | #11

   proberly closer to a 6.5 sack

5. 
   Oak River Mike | Apr 28, 2008 12:09am | #8

   "moist climate"

   Don't forget the termite pretreatment if its required in your region...

6. 
   [email protected] | Apr 28, 2008 07:00am | #12

   The need for a vapor barrier is dependent on how much soil moisture you expect to see, how well draining your base aggregates are (where you are they need to be free draining to help prevent frost heave), and how porous your concrete will be. 

   Not going to get into specifics, but a "standard" commerical driveway is 5.5-inch of 4000-psi concrete, with #5 bars on 18-inch centers, joints on 10-ft spacing.  Depending on where you are, there may be a county or city standard for commercial driveways.  If there is don't build anything less than that.