Replies

1. 
   Gordy_ | Jan 22, 2002 08:50am | #1

   *
   Nick

   Up here in the interior of BC Canada we are concerned with frost for about 2-3 months out of the year. So in standard practice every slab that is poured would have a min of 6" of crush or 3/4 minus compacted under the slab. This crush prevents moisture from wicking its way up to the underside of the concrete inturn heaving when the weather turns cold. After looking at where you live you most likely do not have this frost problem but you should always tamp the soil before pouring a slab. Saves in the long run

   Gordy

   BC canada

1. 
   eddie | Jan 22, 2002 09:20pm | #2

   *you should always compact any sub-surface under a slab, or else you could have settling cracks, concrete slab's aren't exactly supermodel light you know!good stuff

1. 
   Nic_ | Jan 23, 2002 05:00am | #3

   *Do I need to rent a compactor to so this or can it be done by hand? Thanks guys.

1. 
   Johnnie_Browne | Jan 23, 2002 05:36am | #4

   *yes

1. 
   Mike_Maines_ | Jan 23, 2002 06:08am | #5

   *In other words, for a small area use a hand-tamper, for a big area rent a power model. Or do it by hand and build up those delts and traps.

2. 
   Cliff._Johnston | Jan 24, 2002 07:13am | #6

   *Nic,I would suggest that you pour a 5" slab, 3,500 psi, reinforced with 3/8" rebar on 18" centers (placed just below the center of the slab. The base should not only be tamped, but also I would suggest wetting it - as in soaking it. If you use run-of-the-mill sand the soaking with water will help to settle the fines better. I usually spend an extra buck or two and use washed sand as it doesn't settle/compress as much as regular sand - more stabile in the long run is what I want to say.We're here in an area of Texas where "everyone" has cracked concrete, or so most of the local contractors say - well, not quite everyone. I've got about 1,100 sq. ft. of patio & pool decking that I poured in my backyard (to my specs.) about 9 years ago. I did it after 3 contractors told me that all concrete cracks here. That irritated the ... well, I wasn't happy with them. I'm an old union cement finisher. Hmmm, I'm still waiting for my concrete to crack. Good thing I didn't try to hold my breath.By the way, I'm assuming that your slab won't be more than 10'x10', if so then you need to allow for expansion joints - not control joints, but real expansion joints; otherwise, the concrete will crack on its own every 8' to 12' or so on average. I guess that's OK if you like cracks - I don't.I'd also suggest keeping the slab damp for a good 3 days, if possible. A visqueen cover and the addition of water on the slab and under the plastic will do the trick. I'd check on the water every 1/2 day or so depending on the weather and add water as needed. If the plastic rests on the slab you may get some irregular surface coloration on the slab. If this is a problem and the slab isn't too large then you could make a "tent" of the plastic to keep it off the concrete.Good luck,Cliff.

3. 
   Randy_Rogers | Feb 05, 2002 10:06pm | #7

   *Yea Cliff. Concrete and cracking do not necessarily go hand in hand. Too many seem to expect it which gives permission for poor workmanship. Drive on. Randy