"floor" for garage

[N1ST]

I'm putting up a shelter logic fabric garage soon, and think I'd like to dig up the grass, put down a plastic vapor barrier, then crushed rock on top of it. the goal is to keep the humidity down inside, and also provide some type of floor.

With my 4' FEL, would it be easier to try to skim the sod off or would it be easier to til it first?

What type of crushed rock, clay, etc. should I use and how many inches?

Thanks.

 

[joe48]

I'm putting up a shelter logic fabric garage soon, and think I'd like to dig up the grass, put down a plastic vapor barrier, then crushed rock on top of it. the goal is to keep the humidity down inside, and also provide some type of floor.

With my 4' FEL, would it be easier to try to skim the sod off or would it be easier to til it first?

What type of crushed rock, clay, etc. should I use and how many inches?

Thanks.

If you want to remove the dirt and sod and have the tiller, then thats easy. Set the tiller for the depth you want, till it twice with an overlap pattern, then use your bucket w/o teeth. It will skim the loose dirt off the under layer with slow and careful control of bucket angle (dead flat).
lay in your vapor barrier and top with either crusher run with dust for a more permanent hard surface when packed or if ease of removal later use what is know as B 1 B crush, which is a small (under 1/4", bigger than 1/8") stone, washed and uniform in size , packs nice but easily worked with hand tools and easy to remove later if needed. ( commonly used under paver blocks by pros)

 

[EddieWalker]

Humidity isn't determined by the type of flooring you have. It's all about mosture content in the air and the tempature of the air. If you want to control the humidity, you need to insulate and heat/cool it. Ventalation with fans is also fairly effective at cutting down on the amount of condensation that comes with humidity in a shop or barn. In metal buildings, it can feel like rain at times when it's really bad, but the floor type doesn't have anything to do with this. It's all about the water in the air.

If you just want some sort of flooring, gravel is terrible. I'd go with old fashined compacted smooth dirt before I used gravel again. Then in time, pour concrete. If you have limited funds like the rest of us, consider pouring the concrete in sections. You have so much set aside for gravel, so use that amount for a cement pad where you will need it first. Then, when you have more money, do another pad.

Eddie

 

[joe48]

The movement of MOISTURE from the ground to the air inside the enclosure is a legitimate concern regardless of outside air humidity. However air circulation is important to lessen the effects of condensation from humidity as temperatures change.
I have used both tarps and vapor barrier plastic in my shelters. If parking equipment just drive it in and park, if storing other types of equipment or parts etc I usually put them up on pallets so not in contact with ground or tarp and allows air circulation all around.

 

[Builder]

The movement of MOISTURE from the ground to the air inside the enclosure is a legitimate concern regardless of outside air humidity. However air circulation is important to lessen the effects of condensation from humidity as temperatures change.
I have used both tarps and vapor barrier plastic in my shelters. If parking equipment just drive it in and park, if storing other types of equipment or parts etc I usually put them up on pallets so not in contact with ground or tarp and allows air circulation all around.

I tend to agree, especially if your equipment is not used frequently.. Have you ever noticed that equipment parked over grass quickly gathers moisture and will begin to rust even out in the open air. I think "drying out" the ground below it can only hep the bottom of your equipment from wicking up moisture underneath.

Quick story: Years ago, I was going to buy a really nice low mileage F-350 4x4. It was reasonably priced and only had ~8,000 miles on it. I couldn't understand why I drove past it for like a year and noone bought it! Finally I stopped by to test drive it. It was sitting parked on a lawn in front of a business along the road. I was amazed to see how much rust had formed on the frame, axles, etc. under the truck. The owner informed me that the truck was parked over grass most of its' life and combined with low useage, the frame had gathered a lot more rust than a vehicle parked over a dry surface and driven a lot.

 

[LarryRB]

Don't know where in CT you live, around this northeast area, most use Amrec,, This is a combination of asphalt millings, broken up concrete Jersey barriers, 1/2 " stone, and on ocassion you will find new shingles that didn't make the grade, ground up and all this concoction has binder put in., I have most of my 1600 ft driveway in Amrec, most municipalities Ct and lower Massachusetts use Amrec to go over gravel and or dirt roads. Once a rain hits it, it binds right up tight and is hard as concrete.

 

[patrick_g]

The movement of MOISTURE from the ground to the air inside the enclosure is a legitimate concern regardless of outside air humidity. However air circulation is important to lessen the effects of condensation from humidity as temperatures change.

It is with some trepidation that I contradict Eddie but I think the above says it well. Ground evaporation and transpiration of the grass contribute to humidity and in an enclosed space will raise it considerably.

Now for my question... Why go to the effort to work the dirt first? If you are putting a good quality vapor barrier down over the grass and a decent thickness of gravel over that then why bother removing the grass. It will die and NOT be a problem.

A larger problem will be if you use sharp edged gravel and don't put it deep enough to "randomize" the loading from vehicular tires. If you don't want a THICK layer then put down some sand first or fine chat and then top with gravel. This will reduce the punching of holes in the vapor barrier.

In similar situations some folks have used pressure treat or landscaping poles or ... to form a low wall to retain the gravel inside the desired area.

If sometime in the future (and who can say for sure when or if) you want to remove or move the "floor" you can do so using the above methods. It will be easy and not require a lot of filling and leveling. Just move the "shelter building" and its floor and then stirr the dirt a bit and reseed.

Another question might be: Why not go extra HD on the vapor barrier and skip the gravel? You can use sand or kitty litter or diatomaceous earth under leaks. IF slipery is a consideration put on a layer of sand.

Pat

 

[Lynkage]

These all are good answers.
Here is another possibility for you. Use recycled asphalt. You could use a vapor barrier if you wanted but would not be required. The asphalt would provide a non-permeable base if used at 6" thick and out here in Colorado it runs about $5 a ton.

 

[EddieWalker]

I realize that most people don't agree with me on my denial that mosture is coming up through concrete floors. I also don't mind being in the minority on this. It's really a simple thing for me.

If moisture will travle uphill against gravity, through several inches of concrete, then it should do the same in the other direction with the aid of gravity. Test it out, it will never happen.

Why is it that moisture only travels up through the floors of shops and barns, but not in your house? Most every house has openings around there tub and shower dain lines. It's common to leave those openings open. If you take out your tub, you will usually see the dirt around the open space of the drain. The rest of the lines throught the concrete should leak to some small degree. I know they wouldn't be considered water proof when you put a pipe through the slab and pour around it in any pond or lake situation.

If moisture is coming up through solid concrete in a shop, why doesn't it come up through the open spaces inside your house?

As for parking over grass, I think what's happening is the humidity levels are traped under the vehicle and creating condensation on the bottom of the vehicle. More moisture on the grass means higher levels of condensation will form. Over time, this will lead to the rust, because it's never ending.

Has this ever happened to a vehicle parked in a shop/barn with a dirt floor? From what little I know, there have been thousands of tractors and vehicles parked on dirt floors over the decades. Does anybody know of any increase in rust on the bottoms of them? If moisture was traveling up through concrete, those dried out, dirt floors should be letting all sort of moisture through them!!!!!!

I guess that's another point. How do those floors get so dry and hard if there is all that moisture in the ground coming up through them? While I'm at it, has anybody ever been under a pier and beam house? The dirt in those crawl spaces is as dry as it can possibly be. You need to use an electric jack hammer just to dig in it, it's so hard and dry. Why does anybody think moisture is coming up through solid concrete, when the ground under every single building ever built is so much dryer then the surrounding soil?

The mystery has me totally confused.

Eddie

 

[Lasgambler]

When I lived in Louisana we had to put a vapor barrier under all residential slabs. My home in Slidell did not have a barrier under the open carport slab and was almost always wet.
When I lived in Sequim, WA. we built a professional office building w/o a vapor barrier, when the spaces were occupied they used the plastic floor mats behind the desk, the type to make chairs roll easier on carpet. Very soon after they realized the carpet was wet under the mats. IMHO Heating spaces w/o vapor barriers does cause moisture to come up through slabs, I have seen it happen. Just my 2 cents.

 

[patrick_g]

Eddie, Check with a GOOD floor covering contractor. A good experienced floor covering contractor will test a slab for moisture before deciding what sorts of coverings can be used.

One of the simple tests is to tape a piece of vapor barrier to the floor. Leave it for at least 24 hours ( I left several in my basement for a week) and then remove them. If the concrete is darkened it is from moisture. If there is liquid condensation on the top of the slab or on the plastic then that is even a worse case.

Porcelain tile is not permeable and can be "popped" off by the vapor pressure of the water in the concrete.

Concrete is like a wick. Moisture and vapor will pass through it. Radon will pass through it. My basement floor is 5-7 feet under the local water table and is super dry but not because water can't get through the concrete. It is because I engineered the system to prevent water getting to the concrete.

Pat

 

[Rara Avis]

The movement of MOISTURE from the ground to the air inside the enclosure is a legitimate concern regardless of outside air humidity. However air circulation is important to lessen the effects of condensation from humidity as temperatures change.
I have used both tarps and vapor barrier plastic in my shelters. If parking equipment just drive it in and park, if storing other types of equipment or parts etc I usually put them up on pallets so not in contact with ground or tarp and allows air circulation all around.

Ditto...
KISS all the way...

 

[Builder]

I put vapor barrier under ALL concrete. It's not just for vapor coming up, it also prevents all your water from draining out of the concrete, which can cause surface cracks while curing.

Someone asked "why not just leave the grass". Reason: It will cause more settling and smell like the devil when it rots. Also, the scaped-up grass and topsoil will make nice fertile fill around the stone in the garage.

 

[bx23barry]

I really don't know how water moves (except downhill) but I do know around here where my trailers are parked outside, grass doesn't grow under them. Just like it doesn't grow under the house but somehow it can grow through asphalt and concrete cracks (or maybe it makes it's own cracks). Have never seen grass grow in a garage/shop/barn either?

 

[EddieWalker]

Eddie, Check with a GOOD floor covering contractor. A good experienced floor covering contractor will test a slab for moisture before deciding what sorts of coverings can be used.

Pat,

I think this is exacty how people get confused. You are mixing your facts to arrive at a conclusion, but missing what's really happening. And please don't think I'm being rude, I'm trying to type this so it's easy to explain, as that's something I struggle with.

Concrete takes years to cure. The final curing part is a very small percentage of the overal water content, while the initial curing will take place in 24 hours and be hard enough to start construction on. A week after being poured, is solid enough for serious loads, but still not cured.

The test that you describe is for the moisture remaining in the concrete during its curing or drying time. As I'm sure you know, after a few months, there is no more moisture under the plastic that's taped to the concrete. That's because it's cured enough to allow the floor guys to put down their product. If they install the flooring too soon, the moisture from the concrete will either ruin the flooring, or not allow it t bond properly.

This has nothing to do with moisture coming up through the ground under a building that's designed to keep water away from that piece of dirt, nor how water goes against gravity in it's ability to travel through several inches of solid concrete

If this was true, the test would be irrelevant, as the moisture level in the floors would change all the time. Wet seasons, and the floor in your house would be wet. Laminate flooring has a vapor barrier in it thats usualy taped together with masking tape. The tape is just to hold it in place. If the concrete does as some people say it does, then at those seams, there would be failure on those laminate floors. Since the test comes up dry after a few months, there is just another reason for me denial that moisture travels through slabs in shops and barns.

Again, I'm not directing this at you or anyone, it's just my opinion that vapor barriers are not, do not and will not have any effect on moisture developing on a concrete slab in a shop. They do just like Builder said, they hold the moisture in the concrete longer when you pour a slab. The longer the concrete holds moisture, the stronger it is.

Eddie

 

[Builder]

I realize that most people don't agree with me on my denial that mosture is coming up through concrete floors. I also don't mind being in the minority on this. It's really a simple thing for me.

If moisture will travle uphill against gravity, through several inches of concrete, then it should do the same in the other direction with the aid of gravity. Test it out, it will never happen.

Why is it that moisture only travels up through the floors of shops and barns, but not in your house? Most every house has openings around there tub and shower dain lines. It's common to leave those openings open.
Eddie

Not for a long time. I'm required to foam all openings by building code for fire/smoke.

I've actually seen several cases of the interior of a building "sweating" causing lally column poles and interior steel beams to rust. I've bought & fixed up a few old stone homes with dirt floors that have substantial dampness in the basements. That is why foundation vents and vapor barrier is required in all crawl spaces.

I think there's more to it than just one factor. If a floor has dampness coming through the floor in vapors and there's enough drafts of air to circulate & dry the vapors, then it's not an issue, but if the building is tight and vapors are substantial, then condensation will occur.

"Humidity isn't determined by the type of flooring you have. It's all about mosture content in the air and the tempature of the air. If you want to control the humidity, you need to insulate and heat/cool it. Ventalation with fans is also fairly effective at cutting down on the amount of condensation that comes with humidity in a shop or barn. In metal buildings, it can feel like rain at times when it's really bad, but the floor type doesn't have anything to do with this. It's all about the water in the air."

I simply disagree. Pour a concrete floor over damp ground, like rotting grass/topsoil and enclose it with very little ventilation. You will have dampness come through the floor, this will turn the microclimate inside the enclosure into on that is damper than one where a vapor barrier has been used and no moisture can come through the floor.

If the OP builds a airly tight draft-free shelter over a damp floor, a microclimate will be created in the building that will hold more dampness than one with a dry floor. One also must consider expansion joints that will allow moisture to escape from the ground, though the cracks and into the enclosure.

The other consideration is the exothermic curing process of concrete which can be prolonged in enclosed areas. I typically pour the basement slab after a lot of the house has been built.

 

[Rara Avis]

Curing Concrete

 

[N1ST]

Thanks for all the feedback everyone.

Joe48 - The B1B and Crusher run sounds interesting. In addition to storing the tractor and implements, I plan to store some hay and will need to sweep it out periodically. Which would be better for that? Also, I was thinking about using a good quality tarp for durability. Did tarps works as well as vapor barrier plastic?

Eddie - what was it about gravel that you disliked, and what size gravel was it?

Larry - I'm near Enfield. How does Amrec's cost compare to cement (about $100 CU) and who offers it?

Patrick - Framing the floor is an idea to consider. I suppose if I put tarp down over the grass, framed it with 4X4s (at least along the sides), then put down 4" of tiny gravel, amrec, recycled asphalt, etc. the rotting grass smell wouldn't be too bad!

Lynkage - not sure if they have the recycled asphalt around here. How tiny do they grind it?

 

[anojones]

While Eddie's logic is difficult to argue with and there is a lot of controversy over whether or not to use a vapor varrier under concrete, it does seem that moisture can penetrate from below. Whether or not it's significant is difficult to say. The ground under the slab will essentially become a high humidity area and water can travel against gravity by capillary action and also becomes a vapor which will travel from higher pressure under the slab to lower pressure above. I do agree that the environment above the slab including the ambient weather and ventilation could cause moisture to form on the cold slab as it would on a cold metal wall- which in all likelihood causes more damage than any water from below (at least after the concrete has cured enough) to flooring placed on the slab.

 

[Farwell]

During the cold months here in Mid Michigan on any day where the temperature rises there are puddles of water standing on my garage floor. The reason for the moisture is the ground around and under my concrete is frozen causing the slab to be very cold. The warmer air above the concrete contains moisture that condenses on the concrete causing the puddles. The moisture on my garage floor does not come through the concrete because the ground under the slab is sand and water disappears like magic when it comes in contact with the sand. Why this happens in my garage and not in my other buildings, I haven't a clue.
I have to agree with Eddie.