"floor" for garage

[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.