All masonry products wick moisture.
If you cannot isolate the slab from moisture you are liable to have at least some moisture movement.

Be aware that fly ash can cause the acid stain to produce a color other than what is intended. Most concrete stain experts will recommend keeping fly ash to a minimum.

Moisture movement should not be a problem if a proper vapor retarder is used. If ground water is so close to the surface (is this a marsh?) that it would substantially increase water vapor pressure below the slab you need a waterproofing membrane under the slab.

Membranes that prevent excess water from escaping downward may cause more bleed water to surface so the finishing time may increase. Don't work the bleed water back into the finish. Using a low water-to-cement ratio with accelerator and superplasticizer admixtures will offset these problems.

I would ask him what surface treatment would be compatible with the moisture problem he is describing. This issue needs to be dealt with regardless of what kind of flooring is used.

The moisture problem might be caused by condensation on an uninsulated slab below grade in a humid unconditioned space.

In my experience, there is no poorer construction methods to be found than near lakes and other vacation areas. I would make no assumptions about the slabs he is describing.

There is a good reason that pier construction has been popular near lakes and in otherwise wet soil.
It is NOT just to increase wight bearing.
Trying to keep water from wicking into a slab with ANY membrane is just a loosing battle.

Our stained concrete flooring contractor told us and coordinated with the concrete sub for the mix to contain no fly ash. As danniegal points out and we were told, flyash will affect the way the concrete "takes" the acid stain (color). Our floors turned out beautifully and we've had no problems that you've mentioned. It's very wet and humid in our part of the state. No problems.

No offense, but it sounds as if the tile guy is making sure you purchase from him and not use stained concrete. I can point you to the website of the company that did our floors; there is a lot of info there regarding specs, care, etc.

Thanks for the great info ya'll. We were in a house a few months ago, that had sort of a white powdery film in places on their concrete floors, but we didn't know what it was. I assumed it to be left over cleaning product, but we sure weren't gonna ask. So, I guess it is *possible*. They don't do basements down here, and I've never heard of this issue, but I'll ask out a membrane. Might be more of a pain than it's worth.

txgal06, we're also in TX, SW of DFW to be exact. I'd be interested in knowing who you used. No offense taken. The inherent conflict of interest in the tile guy's position is why I posted here. Thanks!

We have friends who's stained concrete did this. However, they were pretty much told "water got under the sealer" but not how. I don't think it was ever said that it could have been from underground and through the slab. They way they told it to me made me think it was from mopping or whatever. As we've been sealing our stained concrete floors (in southern OK) I've been thinking of them wondering if my mopping the floors was putting too much water on them before we sealed them today.

So basically I don't know the answer for sure but I have seen in person a sealed concrete floor messing up and becoming cloudy.

I'd think a lot would depend on your soil and the position of the house realitive to the lake.

"We were in a house a few months ago, that had sort of a white powdery film in places on their concrete floors, but we didn't know what it was. I assumed it to be left over cleaning product, but we sure weren't gonna ask."

Far more likely is efflorescence.
Moisture wicked through the concrete dissolves various salts.
When the water evaporates on the surface the salts are left behind.

It's really not difficult to design a slab so that this problem doesn't occur no matter where the building is located.

Here is a link that might be useful: vapor retarders

Even if it is below the water table you can waterproof it.

Here is a link that might be useful: slab waterproofing

We have a place in our kitchen where there is an exterior patio off of this particular wall. The exterior patio has a crack that runs lateral to the wall that is not huge but not a tiny crack either. Off of this larger crack that is outside a smaller hairline crack runs towards the house and all the way through to the kichen. It is a tiny, what I would consider normal crack. When its cold and it rains you can see dark, damp spots on the kitchen floor where there is moisture following this tiny, hairline crack. It's not really "wet" but it is obviously wicking the moisture from outside. We are going to caulk the large crack outside and see if this stops it but I'm wondering if this should be alarming to us or not. The house is a year old and while the exterior patio is not covered under warranty, the foundation itself is. Should we be really concerned? Thanks for any input.

Exterior masonry of any kind should not continue from outside into the enclosed inside portion of the house; there should be a break containing flashing and/or waterproofing. If such a barrier has been omitted, it will most likely have to be installed. Sealant or caulking is only a temporary repair at best.

There is no way to know how to solve your specific problem without seeing a detail of the indoor/outdoor condition.

If there is water in contact with solid masonry or a crack it will move through it by gravity, hydrostatic pressure, or capillary action (wicking) but in a properly constructed slab, a layer of coarse gravel or crushed stone (not fine materials like sand or clay) prevents water from being wicked up to the bottom of the slab (unless there is hydrostatic pressure present). Water vapor moves through a material if the air above the slab is drier. In a properly designed slab a sheet vapor retarder is sufficient to prevent water vapor from passing through the slab. In the case of hydrostatic pressure a waterproofing layer is required below the slab.

None of this is difficult; it's standard concrete construction practice in commercial construction but it appears to be often ignored by home builders.

If the vapor barrier that was installed prior to slab pour
is not well sealed you will have moisture.
Do you have pics of the site before the concrete pour?
Did you look to see that the vapor barrier was continious..
no tears that were not patched & around gas/water pipes?
If the vapor barrier is not continous you will have
problems ..some sooner, some later depending on flooring type. Some will show problems sooner, others like carpets,
wood & laminates will take longer.

best of luck with you build.

Vapor retarder manufacturers usually insist that it is essential to avoid punctures and unsealed overlaps in their products but this has not been found to be particularly critical in the field by Joe Lstiburek and others.

What is probably more important is the presence of a capillary break (crushed stone, etc.) directly under the slab and the absence of a sand bed above the vapor retarder that can absorb moisture and cause trouble later.

I've been fighting a losing battle with our concrete floor (the whole house is one big slab) for 6.5 years. I washed all the floors yesterday and today they're all white and cloudy looking, and if I wipe with a clean paper towel, it's BLACK!

I had a sudden inspiration this morning that the concrete is wicking something up to the surface, and sure enough, found the answer in your comments. Thank you! I thought I was a lousy housekeeper because I just can't get the floors clean!

I HATE stained concrete. Actually never wanted it, but there was no other house on the market when we bought here in the desert. I've tried all kinds of mops and cleaners and nothing works. Now I have some semblance of sanity. Thank you again for your comments.