Concrete specifications for pole building

[smfcpacfp]

Several months ago, I started a thread about having a pole building built. It is going to be a Cleary building (30 by 48 by 14 feet) and appropriate for the kinds of snow loads (20 to 30 feet per year) we get in the UP of Michigan, and they will build it during the last week of October.

The proposed contract calls for 4" of concrete with wire mesh. I was wondering what you guys thought of this. The soil is pure beach sand, thus there is no heaving in the winter. I read somewhere that you should have 5 to 6" thick concrete if you are going to have heavy vehicles like the RV that will be stored in it.

As someone said either here, or elsewhere, it is cheaper to get concrete right the first time, than to redo it. So what would you guys want for concrete specifications?

 

[AlanB]

I went 6", rebar and remesh not the rolls.

I doubt there would be a problem with an RV on 4". I was concerned with backhoes, dozers etc that have some really heavy point loads.

I would at least go up to 4000 psi concrete, you are probably getting speced 3500

Problem with putting rebar in 4" concrete is it sometimes creates a weak point in itself if it get's to close top or bottom. If you think about it, 4" concrete is usually only 3 1/2" then put a 1/2" piece of rebar in there and you have 1.5" on each side if it is perfectly centered. 6" gives you a little more leeway to work with.

This is what I ended up with, not sure it is right, but nobody said it was not enough, and plenty said it was too much, but the only downside I heard was the extra money I "wasted". I figure if it cracks and comes apart now, I will feel I did everything reasonable. If I had done less, it would eat me up.

 

[smfcpacfp]

Thanks for the reply. I don't mind wasting a little money if it works. To be frank, you never know what you will end up putting on the concrete.

 

[rambler]

Yea, 4 inch would be ok, but concrete does crack - you'll have it scored to control the cracks - and if you have as much salt on the roads as we do, the salt will go in the cracks & rot the wire mesh to nothing in a couple of years. The rebar would be much better. Just in general, rebar is a better thing than wire mesh for several reasons.

--->Paul

 

[smfcpacfp]

Fortunately salt won't be an issue.

 

[Carykong]

your pad is 30x48. if you expect to have a dedicated area for your RV or any other heavy equipment, you could pour the dedicated area 6 to 8 inches thick and go 4 inches for the remainder to save money. wooden planks over your pad for heavy equipment will spread the pressure points,too.

 

[MichiganIron]

The best concrete mix can be ruined by a contractor adding too much water to the mix. A 4000psi mix can be destroyed by adding too much water when the truck arrives. Many flatwork contractors like to add extra water in the truck to make it easier to flow the concrete and trowel the surface. Too much water leads to excessive shrinking during cure, cracking, and aggregate seperation leaving the top of the concrete smooth, but soft.

Concrete water content is measured by "slump". Take a shovel of concrete from the batch and drop in on the ground from knee height. It should leave a pile 4-6" high. If it flows and looks watery, refuse to let them place it.

 

[Duffster]

The best concrete mix can be ruined by a contractor adding too much water to the mix. A 4000psi mix can be destroyed by adding too much water when the truck arrives. Many flatwork contractors like to add extra water in the truck to make it easier to flow the concrete and trowel the surface. Too much water leads to excessive shrinking during cure, cracking, and aggregate seperation leaving the top of the concrete smooth, but soft.

Concrete water content is measured by "slump". Take a shovel of concrete from the batch and drop in on the ground from knee height. It should leave a pile 4-6" high. If it flows and looks watery, refuse to let them place it.

And if it is to stiff to work you will end up with a big pile a **** too.

 

[mjncad]

I second AlanB's suggestions. Do it right the first time, because it will be far more expensive to fix later.

If your budget allows for it, have the control joints sawcut instead of tooled just after the pour. There is nothing more frustrating than moving something on casters only to have it jolt to a sudden stop when a wheel catches in the control joint.

 

[foggy1111]

I just had a 30 x 40 Cleary building built to store my boat and tractor and implements. I put down 4" of 4000 lb concrete with 1/2" rebar on 2' centers which was supported to the middle of the floor. I had a vapor barrier placed under the slab and had it saw cut a few days after the pour. (I think 6 or 8 sections?)

I also put a 8 foot apron on after the floor pour....and had rebar drilled into the garage floor to connect the apron. (things freeze / thaw here in MN......and I hate the "step" caused by not tieing the floor to the apron). I also had the concrete sealed when poured.

The apron has proved to be the real deal on hot days. I can service my tractor or implements outside on a hard / flat surface in a breeze.