Building my first Pole Barn with Concrete Slab - Help on first steps

[sdkubota]

You are going to need 84 Tons of gravel for a 6" base.

 

[sdkubota]

There is more uplift forces on large buildings than downward forces due to wind. Install the posts to the depth the manufacturer recommends and it doesn't matter where your frost depth is.

 

[Mark Page]

When I built mine the posts were first thing I installed. Brace them in 2 directions and back fill with dirt. The dirt will settle while you continue to build. As soon as you have the siding boards in place you can pull the post braces. Plan on building it a little high so you can grade a slope away from the building. Setting the posts deep may seem unecessary, but the extra depth will help prevent racking.

 

[jimmysisson]

All good comments. One that should be emphasized is compacting the fill material. You only get to work on what's below the slab once; a broken slab is REALLY annoying. Also nobody talked about drainage - you want to be sure storm water is diverted away from the building.
Judging from that you have equipment, you probably know all this, but talking to an experienced pole barn builder isn't a bad idea.
Jim

 

[kneedeep]

When I built mine the posts were first thing I installed. Brace them in 2 directions and back fill with dirt. The dirt will settle while you continue to build. As soon as you have the siding boards in place you can pull the post braces. Plan on building it a little high so you can grade a slope away from the building. Setting the posts deep may seem unecessary, but the extra depth will help prevent racking.

I really like the shed- Good Job!! :thumbsup:

 

[lgranch]

One thing I did is add welded wire mesh (6X6) on top of the fill gravel to stop the concrete from cracking. I know others will say that the fiberglass reinforced concrete will work just fine but it has been my experience that fiberglassed concrete cracks any direction and width it wants to. With WW mesh I have had no more than a 1/16 of an inch crack along the zip strip lines on my workshop floor. No cracks to deal with. Just my 2 cents.

lgranch

 

[sdkubota]

Actually, regardless of what you do the concrete will crack. As an engineer, I consider metal mesh to be the least effective because it gets trampled down while placing the concrete. Poly fiber mesh gives the concrete additional flexural strength and will stop microscopic cracking but not normal shrinkage cracking. The thing to do is have the entire slab sawed 1/3 concrete depth within 24 hours in a no more than 12' grid both ways. This allows the stress cracking to occur in a straight line which is easily maintained. A 10' spacing would be better for a 6" slab but I will warn you if you go to 16' it will randomly crack between saw cuts and you will have wasted the money sawing.

 

[lgranch]

You are quite right, sdkubota, the concrete will crack regardless. However, it has been my experience that concrete with properly installed ww mesh, will not continue to crack wider and wider. I'm not saying that the fiber is bad I'm just saying that with the fiber only that the cracks that do occur will continue to widen while with ww mesh the cracks will not continue to widen. Once the fiber has been broken by the concrete cracking there is nothing to keep the concrete from continuing to crack because at that time the fiber is no longer able to support the concrete.
Here in the northwest we use a product called a "zip strip" that is placed just under the surface of the concrete where you want it to crack. So instead of sawing the relief cuts the zip strip slightly weakens the concrete where the crack is desired to form and concrete being concrete obliges.

Just my experience,
lgranch

Actually, regardless of what you do the concrete will crack. As an engineer, I consider metal mesh to be the least effective because it gets trampled down while placing the concrete. Poly fiber mesh gives the concrete additional flexural strength and will stop microscopic cracking but not normal shrinkage cracking. The thing to do is have the entire slab sawed 1/3 concrete depth within 24 hours in a no more than 12' grid both ways. This allows the stress cracking to occur in a straight line which is easily maintained. A 10' spacing would be better for a 6" slab but I will warn you if you go to 16' it will randomly crack between saw cuts and you will have wasted the money sawing.

 

[sdkubota]

Zip strips would work fine and might save some dollars. All metal reinforcement does not take any load until the concrete cracks. Once cracked, moisture can get to the reinforcing steel but inside a building will be minimal. If you are in a zone that freezes frequently and the slab will be exposed to freezing temps then have the concrete "air entrained" at 6% at the concrete plant. This provides microscopic bubbles of air that help reduce the pessures due to freezing within the slab. The best thing that can be done, doesn't cost a dime, but hardest to accomplish is do not let the conctractor add water on site to make the concrete easiler to place. Nothing over a 3" to 4" slump should be allowed. Generally only deeper sections of concrete are reinforced with re-bar and those are to take tension loads. Anyhow, centuries of studying the stuff and it still cracks and still gets hard.

 

[jimgerken]

I'd love to use the stuff you call "zip strip", but cannot figure out how to get it in place in the slab. Would anyone with hands on experience please explain how and when to use the strip stuff for crack control on a slab? Thanks!