Pole Barn Advice

[EddieWalker]

Human nature being what it is, you'll find that most people who do not pour concrete at the begining, rarely ever get around to it. Gravel is a terrible floor no matter what you use. The rocks will work there way to the surface and you'll have to deal with them forever. If there are bigger rocks, you WILL twist your ankles on them. If they are small rocks, then there will be movement of them all the time. Once you start using the shop and storing stuff in there, it's just that much harder to getting concrete poured.

No matter what your budget is, pour concrete from the start. If you have to wait another year, then wait. Doing it any other way will just cost you more money over all. If it was me, I'd figure the size of building that you want to build, make sure it's what you really want, and pour the slab. Once it's poured, you can work on building it over time. Frame it and put a roof on one year, do the walls the next year and so on. There have been threads here where members have spent several years working on their barns. It's not a bad way to save some money to get the most you can with the best results possible.

Good luck,
Eddie

 

[westbrooklawn]

Don't guess. Call around to concrete contractors and find out what type of gravel they recommend. Also ask if a plastic vapor barrier is needed.

I had a 24x42 ft concrete slab poured in June05. The contractor recommended a 6 mil thick Visqueen vapor barrier under the gravel.

My slab is 6" thick, 4000 psi concrete, #4 rebar criss-crossed on 24" centers.

The recommendations I have gotten are to put the vapor barrier on top of the gravel... this post caught my eye because it is contrary to that.

Which is right??

 

[EddieWalker]

The Great Vapro Barrier Debate.

I'm in the minority here in that I don't agree with those who think a vapor barrier keeps water our of a shop. My experience is that water does not go uphill, against gravity, through solid cement.

What a vapor barrier does do is to keep the moisture in the concrete and allow it to cure slowly. When you pour concrete, you want several things to happen. You want it to be as dry a mix as possible. This gives the cured product it's maximum strength. You also want it to have a certain amount of moisture, which it will when mixed, and to retain that mixture when poured. This can change in dry soils, or soils that wick moisture out of the wet conctret mix. If this happens, you will have an uneven mixture, which means a weaker pad when cured.

This means the concrete should be poured direction onto the plastic vapor barrier.

Eddie

 

[TwinWillows]

Perhaps putting it under the gravel is a regional practice I'm not familiar with.

The vapor barrier I'm familiar with always goes on top of the gravel, insulation (if any) on top of that, mesh/rebar on top of the insulation...

 

[woodlandfarms]

My very minor 2 cents on this. Gravel blows. I spend a lot of time kneeling and on my back with my tractor and the gravel in my carport hurts, hurts hurts. I know nothing about rock and gravel (Except what I have learned here thanks to all of you) so maybe the stuff I have is not ground fine enough, but we have a big water problem here with our rain.

 

[thunderworks]

The Great Vapro Barrier Debate.

I'm in the minority here in that I don't agree with those who think a vapor barrier keeps water our of a shop. My experience is that water does not go uphill, against gravity, through solid cement.

What a vapor barrier does do is to keep the moisture in the concrete and allow it to cure slowly. When you pour concrete, you want several things to happen. You want it to be as dry a mix as possible. This gives the cured product it's maximum strength. You also want it to have a certain amount of moisture, which it will when mixed, and to retain that mixture when poured. This can change in dry soils, or soils that wick moisture out of the wet conctret mix. If this happens, you will have an uneven mixture, which means a weaker pad when cured.

This means the concrete should be poured direction onto the plastic vapor barrier.

Eddie

Eddie,

I have very direct experience contrary to your belief that water does not go through concrete . . . Remember, the issue is not water, but water vapor, which while obviously a form of water, behaves differently than standing water. Vapor responds to temperature gradients, moving when there is a temperature differential between ground temp and the airspace above. Molecular water easily passes through concrete. I manage a commercial building for a group of partners where the slab-on-grade did not have a vapor barrier installed during construction. The building has had perpetual problems with moisture condensing under plastic chair mats which are used in the office - so much moisture in fact, that the plastic mats actually turn a milky white. It's an unbelievable problem.

 

[EddieWalker]

I can't argue people personal obsevations, but in several years of this debate, the moisture in the building can almost always be credited with condensation. The believe the water turns to vapor and then passes through concrete from under a slab isn't something I belive is possible. There is an entire chain of events that would have to happen that nobody can explain.

Just because there is moisture in a building has nothing to do with whether there was a piece of plastic put under the slab when it was poured. In fact, a little known secret that those of you who think that piece of plastic keeps out moisture might not know is that the plastic sheet has holes in it. Just think about the utlity lines and explain why there isn't mosture around those areas?

I also did a little experiment with a piece of concrete and a puddle of water. It was told to me that concrete wicks moisture up from the ground through the concrete. I put a 4 inch thick piece of concrete in a water puddle that was an inch deep of water. Does anybody think the water worked it's way up the sides of that concrete to the surface? It does wick it's way up a bit, but not very much. Why can't standing water do this, but some of you believe that minute particles of vapor can?

It's all condensation.

Eddie

 

[flusher]

Don't guess. Call around to concrete contractors and find out what type of gravel they recommend. Also ask if a plastic vapor barrier is needed.

I had a 24x42 ft concrete slab poured in June05. The contractor recommended a 6 mil thick Visqueen vapor barrier under the gravel.

My slab is 6" thick, 4000 psi concrete, #4 rebar criss-crossed on 24" centers.

Oops. My mistake. The plastic goes over the gravel, not under. Sorry about that.

There's the gravel covering bare ground

There's the Visqueen and rebar covering the gravel

 

[Kendrick]

eddie as I understand it, it is a swamp cooler effect. if the soil was warmer then the top of the slab, the slab would draw the moisture down to the ground through capalery convection? Since we like it 74+ and average ground temp is 68- subserface, evaperation trys to equlise it.

 

[rambler]

If you plan to do something with the floor in 12-24 months, leave it dirt now. Do the floor when you can at that time. I have a machine shed dad built in 1964, it is still a dirt floor. Can find the grass roots..... You will be 6 inches too deep, and working in gravel, and improperly compacting it, and what about insulation, if you try to do a sub-grade floor now & wait to pour the concrete. Or you will be hauling material in now, only to scrape it out & redo. Just wait with the whole deal if you are going to wait. Work in the dirt for 12 months, it will remind you to get around to finishing it.

Do do something with the roof insulation as you build it. It is miserable & very expensive to add roof insulation to a metal building after it is up. Check into this. If you want an insulated building, do the roof as you build! Do not try to insulate later.

Walls you can insulate later, hanging batt is probably cheapest, sounds like you are on a budget & won't be doing any foam once you price it or you would just do the right isnulation from the beginning & save money now.

Concrete will pull water through the floor. Check with anyone with a grain bin in the upper midwest. Those with plastic are good, those without you throw away the bottom 3 inches or so of molded rotten wet grain plus you have a crust on the top of the grain that isn't too good from the vapor that travels up. Nothing to guess about there.

--->Paul