advise for concrete floor for wire corn crib, or wood floor?

[LorenMN]

I'm going to be putting up an 18' diameter 1000 bu. wire corn crib, and I'm looking for any suggestions for the floor. I'm going to dig out the top soil and tamp in class 5 gravel. Thinking that a concrete floor would be 4" thick, and I'd dig down along the perimeter for 12" deep x 6" wide footing, to keep rats from digging under it. I don't have a drag so I don't need a trench in the floor. I will be putting down the U-shaped ventilators on the floor before filling the bin. I have 4 acres that I will be picking as ear corn, and grinding for steer feed. Hoping I will get a 2 year supply so I can alternate to oats next year.

Is pouring this floor something that I would want to try doing myself? Largest floor that I've done before was 6'x9', haven't done anything that I couldn't put a 2x4 across to get level. Would I want to use fiber filled concrete? Any guesses on cost?

Or....Would I be better off to use green-treated 6x6's with 2x8's screwed to them, and set the crib on that and forget about concrete? Seems like that would be easier and cheaper for me to get done, since I only have about 2 months left to have the crib ready to fill. The space between the 6x6's would leave room for the cats to get under there to control the rodents. If I make the base square, I could dig a post hole under each corner and cement in an anchor for each corner. This option would be a less permenent too, so I could move it if I ever need to.

 

[Anonymous-0]

Just a thought, but a concrete floor then a wood slat(??) floor on top would keep air circulating so the bottom don't mold and the cement don't deteriorate...

 

[Larry NEIL]

Pour the floor. You should get some help pouring it. To level the slab, pound a stake in the middle, pull a line tight across the forms and mark grade.
Not hard to do, but laying down concrete is the important [art, so some help is needed to pour and level properly. With concrete, you don"t have time to "learn".

 

[rrlund]

Don't underestimate the weight of it. The wood floor would have to be awful stout. I've poured quite a few. We put a pipe in the center then used a 2x4 with a nail in it to get the level right. We set the pipe so the center is a few inches higher than the outside so water doesn't run in under the corn.
Do what you want to do as far as a place to put a drag in it. I didn't put one in any of mine but as I got older,I sure wished I had.

 

[MN Scott]

A bushel of ear corn weighs 70 lbs. So your crib when full will weigh 70000 lbs. Thats alot of weight for 4 inch's of concrete. I would go with at least 12 inches, 14 would be better. Make sure your base is deep enough and well compacted.

 

[Traditional Farmer]

Put plenty of rebar under the slab and I'd pour
it 6" deep with 3500PSI concrete with fiber added and yep you'll need help of an experienced concrete finisher the last thing you want is for that slab to hold water.I'd have it a little high in the center and slight drop to the outside.

 

[Traditional Farmer]

If the CONCRETE (not cement) is any good it won't deteriorate,the wood will rot eventually and it'll give the rats an opening.

 

[jal-SD]

Definitely slope away from the center. Concrete guys like to pour stuff flat and level, but don't forget that water needs to run off or it sets in one spot. Even if the floor looks to be dead-on, it will still puddle someplace. When designing “flat” surfaces on something like you are planning, we always figured at least 1/10 of a foot (about 1 & 1/4 inches) of slope to each 10 feet of run to keep water from puddling on the surface. In your 18 foot diameter crib, I would figure at least 2/10 of a foot of slope away from the center to the sides of the circle. 2 - 1/2 or 3 inches wouldn't hurt a thing in 9 feet and you will never notice the rise. If you pack your base well, you can slope that too and save a bunch of concrete. It’s REALLY IMPORTANT to have good base compaction to prevent the concrete from settling and cracking over time. I would also use wire mesh or plastic fiber in the concrete to aid in preventing cracks. The plastic stuff that is available works well for that. It’s less expensive than wire. (Talk to your redi-mix guy.) I’d use a six bag mix, too for a 4" floor due to the weight requirements. This advice comes from a retired engineering technician. (My $0.02 worth. jal-SD)

 

[LorenMN]

I made a typo, it's a 16' diameter crib, not 18', but still 1000 Bu.

Sounds like concrete is the way to go. Only want to do it once, so I better do it right. Didn't think about sloping it, but that does make a lot of sense.

So for a 16' crib, should I go 17' dia. on the concrete?

 

[rrlund]

I wouldn't go but a few inches more than the diameter of the crib. When water drips off the eves,if it hits the concrete,it'll splash back up on the corn.

 

[LorenMN]

Just checked with the redi-mix plant. 5 yds. of fiber filled concrete is $822. Then adding the cost for labor, ouch! Wife ain't gonna be happy.

Thinking more about a green treated floor again. Maybe use eight 6x6's on 24" centers, covered with twenty 2x10's. I have a roll of stainless steel wire mesh I could put under the 2x10's to keep rodents from chewing thru.

 

[RayP(MI)]

My thoughts exactly, domed in the center, so any water will run out to the sides. Would be a good idea to place a plastic vapor barrier under the slab to prevent moisture from coming up through the concrete too. A wide eave(s) around the top would be helpful to keep rain out too.

 

[RayP(MI)]

Also a good idea to precut some grooves in the surface so when it cracks - and it will, it will crack in a controlled manner. Check with your extension office to see if they have any plans availible.

 

[Rich_WI]

(quoted from post at 14:05:08 08/10/12) Just checked with the redi-mix plant. 5 yds. of fiber filled concrete is $822. Then adding the cost for labor, ouch! Wife ain't gonna be happy.

Thinking more about a green treated floor again. Maybe use eight 6x6's on 24" centers, covered with twenty 2x10's. I have a roll of stainless steel wire mesh I could put under the 2x10's to keep rodents from chewing thru.

I dont think you are gonna build a wood base cheaper but thats just a WAG, I didnt put a pen to paper to come to that conclusion. In any case, labor shouldnt be too bad if you get some friends to help, you can get alot of work done with beer and pizza. Even still, with no friend-power you can do it yourself. Its not rocket science, its a dumb grain bin. Normally when friends ask how to pour concrete and start talking about how they are gonna build their own house or something (big project with zero knowledge), I tell them to hire a pro and recommend a few. In this case though, its a perfect time to learn a little and to save some money. Make a plan, take some notes and do it.

I wouldnt go with only 4 inches of concrete, I think they are specing 5 inches for sidewalks in town. I dont think you need 14 inches either but I can tell you one thing, its ALWAYS cheaper to put down more concrete than to tear up and re-pour a thicker pad of concrete. A couple hundred in extra concrete is money very well spent.

 

[Rich_WI]

(quoted from post at 18:32:28 08/10/12) Also a good idea to precut some grooves in the surface so when it cracks - and it will, it will crack in a controlled manner. Check with your extension office to see if they have any plans availible.

Surely you jest. He wouldnt need joints in a slab like that unless he goes with a slab 6 inches or less (which is not recomended). But you also need to factor in the fact that he is pouring a [b:5df007df3f][i:5df007df3f]round[/i:5df007df3f][/b:5df007df3f] slab. That gives you some extra grace. If he pours 8 inches or thicker and uses large aggregate, (highly recomended), you shouldnt put a control joint any closer than 15 feet.

Here is a basic table showing slab thickness and control joint spacing.
http://www.cement.org/tech/basics_joints.asp

 

[Leroy]

Havent use it for several years but have a 12' x 12' crib that I think was about 600 bu. and it is on a wood floor, also a 10' x 10' and again on a wood floor. Both of them I made for use with a drag. They are just set on block pillars and the frame is an octogon (8 sides) and made of homegrown 2 x 8" timber with a 1" board floor. Had a coupel of others on concrete but the wood floor kept the corn in better shape, fact is even tho the concrete floor was higher inside than outside (crib set in the concrete) 2" of water would always be in the bottom of the crib. And the wood will probably last you as long as you are going to be able to have a corn picker. No need to put in something that you will have trouble getting rid of in a few years. I would definatly make it out of wood and with a drag spot even if you do not now have one becase in a couple of years you might find out you want one if your back starts hurting from the shoveling.

 

[JDseller]

I have poured 12 of those corn crib foundations. The way you out lined would be fine. It does not need to be more than 4 inches thick in the center. I drove a 1/2 pipe in the middle to measure off of. I then dug a footer 18 inches deep and maybe a foot wide around the edges. I made the middle crown up a few inches. I used 1/2 plywood for the forms. You can bend it to match the radius you need for the outside. Leave the pipe in the middle and drive a couple of big nails in the edge of a 2x8 an use it as your screed board. Leave the pipe a few inches higher than the sides and you will get your dome easily.

The edges carry the weight of the sides of the crib. I did use 4500# concrete and wire mesh for reenforcement. None of the ones I have ever cracked. I did not put any fill under them. I like hard virgin ground. Fresh gravel will not pack tight enough and it will cause the concrete to crack. Measure the crib and put your anchor bolts in while the concrete is wet.

Like I stated I have 12 of these and they all where poured just like I out lined. I did the first four by myself. You DO NOT need to hire anyone to finish the concrete. Just float it off and hand finish it a little. The ears of corn and mice/rats will not care.

 

[donjr]

I used a piece of 3/4 inch pipe as a center point, and cut sheets of 1/2" plywood for a form on the outer perimeter. Dropping a barn spike into the pipe, and marking a twine made it easy to lay out my outside edges, and then we remarked it and set large tincans with the open end half mashed where our anchors would go, then poured the form and used the twine once again for checking our scree on the concrete. We then erected the crib, placed our anchor clips on the base ring, and concreted in the anchor bolts into the tincan forms. Made it real easy....