Why do I have moisture under vinyl in a newly built concrete slab home?

Question

We have been in our new concrete slab house for 15 months. My kitchen vinyl ripped and we noticed moisture underneath. The flooring people ripped up all the vinyl after confirming there was moisture in all the areas of the home covered w/ vinyl. Nobody can figure out why the moisture is there. They have checked for busted or leaky pipes, ran cameras in the septic system and drilled holes in the outside concrete to see if water was pooled underneath the slab with negative results. They think it my be "black slab" which means the concrete did not cure before the vinyl was laid. The concrete was grey prior to the vinyl being laid, but it is now black. I fear that is mold. The flooring people have brought out a moisture meter several times and the moisture levels are off the charts. They have brought in dehumidifiers to try and dry out the concrete which hasn't worked. We don't know what to do. If the concrete didn't cure properly, will it have to be repoured? Please help!!!

Answer 1

My son just got an estimate to dry out his basement, as he has already put a wood subfloor down and it was $6,000 to put in a drainage tile around the exterior wall-in the floor. Reseal with plastic flooring, level with laser transit and pour all new concrete. Even tho he used treated lumber, they showed him pix of mushrooms and other mold that will grow on that lumber in no time at all. You have to get rid of the moisture before you can do ANYTHING else. Good luck!

Answer 2

This is unbelievable to me that "flooring people" have not explained to you "hydrostatic pressure". Geeezzz.

This is moisture coming through the slab from the ground.

Ordinarily when the slab is poured, sheets of "viscuine", plastic sheeting, is placed over the ground before concrete is poured, which usually prevents this.

Having this much moisture in such a short time causes me to "question" whether the above procedure was performed.
Certainly. I have no way of knowing that.

It may be possible to check this by digging down to the base of the slab at a point along the outside wall. Not a large area. The viscuine may be visible at the edge of the slab.
Do not dig along the garage. It's seldom or never used there.

Hydrostatic pressure is common over the entire US. Some areas worse than others.

If viscuine was used, the moisture is unusual. The only material that is suitable is a "floating installation" of laminate flooring. I see no need to describe that. Any flooring company can do that.

Even ceramic will be subject to moisture bleeding through the grouted joints. That can be killed back with vinegar and water when mopping.

I can't suggest any actions for any possible neglect. The flooring company may have had some responsibility to test for moisture before installing vinyl. Very often overlooked.

Good luck.

Answer 3

Okidoke.... after 15 months....if youve not noticed any really large cracks, or a large number of cracks in it...then your concrete is cured... no need to destroy the home to replace it, heheheh. "Cure" for concrete, means literally, to dry til it hardens up. A curious feature of concrete tho... is that it will act as a wick for moisture... it will literally suck moisture up thru it, from the ground underneath, or along the perimeter. As for moisture meters.... "off the charts" is a relative term...many meters are only designed for a small range of detection, and it doesnt take much to exceed their ability to register the amount of moisture. Ive used a lot of these meters over the years.

If there was even a few days between when the concrete was poured, and when the vinyl flooring was installed, then you should not be concerned over the 'curing' of the concrete. (even if it was rainy weather, the concrete should have cured properly in a few days at the most)

MOST likely... someone didnt put down a vapor barrier before they poured the concrete. Even if a layer of plastic was used...if it was torn, had gaps, etc... moisture could be leached up from the ground underneath. Not to mention along the perimeter, where the ground is in contact with the concrete. Concrete will suck an unbelievable amount of moisture up thru it....if you lay a metal object on a sidewalk, or garage floor... you know where it will rust first? Wherever it is in contact with the concrete.

IF you decide to go with a "floating floor" as someone here has suggested... be certain that a vapor barrier is installed. The foam backing found on most laminate floor systems is NOT a vapor barrier. I recommend a good look at the installion instructions at Pergo's website before considering any kind of laminate floor.

If the 'black' substance is mold... mopping it with a 50/50 solution of bleach and water will kill it. Be sure to open the windows when you do this... you need plenty of ventilation. I would suggest mixing a little in a spray bottle first... and testing one area. Try cleaning the 'black' without bleach in one area, and another with the spray bottle. If it is mold, it will reappear quickly at the location that was cleaned without the bleach.

Dehumidifiers take time to work....remember they are trying to remove moisture from the air... so.... if you are running any air conditioners, or are in a "moist" climate, or have had a rainy day... they will have more work to do..to remove the moisture already in the air, before the moisture on the concrete can evaporate to be picked up by the dehumidifiers.

Someone mentioned that you could have a case where you actually have ground water being 'forced' up thru the concrete... a simple test for this, is to dig a small hole in the back yard, and see if any water percolates up into it. I would suggest that you dig this hole deep enough to pour a gallon of water into it. Give it 24 hours and see if any water has filled the hole. If youve not had any significant amount of water pooled in it, then a day or so later, pour a gallon of water into the hole.... and check the water level a half hour, and an hour, after youve poured the water in. This is a 'perc' test... and is used to check how well your soil drains.... the actual amount varies from region to region, but your local building inspector can tell you what is required in your area. It is possible that youve got a high moisture content in your soil, and the concrete is pulling that right up into the home.

Now, back to getting the surface dry... I would suggest that you 'dry mop' the floor several times... wringing out the water you collect in the mop... this will help your dehumidifier. Do that bleach test to verify if it is mold. (By the way... a damp mop will pick up more water than a totally dry one). Setting a fan to blow on the kitchen floor will help too.

Once you have the floor 'dry'... and you begin to consider what type of floor to install.. I recommend staying away from anything made with an mdf core (medium density fiberboard). MDF is a wood substrate made out of resins (glue), and wood flour. (literally, the wood is ground to a fine powder, like flour) MDF is VERY susceptible to moisture damage, and should NOT be used where there is a concrete subfloor. If you want a floating floor, use a product with a plywood core...it will tolerate the moisture much better, but using a vapor barrier is very important with any floating floor.

Good Luck!

Answer 4

You need to determine what the frost line is in your state and dig footers on the edge of your slab down 6" to 1 foot below the frost line. The footers should be at least 6" wide at the bottom and should slope up to the bottom of the slab on a 45 degree angle. Your slab should be at least 4 inches thick, 6 inches is better. It would also be better if you had rebar in your footer and at least some welded wire in your slab.You will need to dig out the slab to get the elevation of the slab above the ground to where you want it. Make sure there is clean soil below the slab, no organics. You may need to over excavate and backfill to get a good base. Make sure you compact the area with a plate compactor and the soil should be damp but not wet. If you have to oversxcavate and backfill, bring the level up in 6 inch lifts and compact between lifts. Dig the footers last so you don't disturb the main slab area. Put down a plastic sheet as a vapor barrior on top of the soil. Do not let any of your rebar touch the dirt, should be 1 to 2 inches from the edge of the concrete (bottom surface). Vibrate the footers when you place the concrete to assure you don't have any voids, but don't leave the vibrator in one place too long or you'll seperate the aggregate from the concrete mix.

Answer 5

Moisture Under Laminate Flooring

Answer 6

That could be. However, if you life in a particularly warm and humid state it is VERY common (especially if you don't put a pad on the slab before you frame the house, etc.). Air conditioning exacerbates this problem because concrete cools quickly and remains cool, which helps condensation. If your vinyl isn't 100% sealed around all edges, and at the seams, condensation forms directly on the slab.

Answer 7

Water doesnt come from nowhere,it was either still in the concrete or its getting from somewhere.Is it possible to dig a trench around the slab and fit drainage pipe?This trench would have blue metal (crushed rock) and ag pipe fitted and terminate at the lowest point so that any access water can drain away.Just below the level of the concrete.

Answer 8

Fact: You have no moisture barrier under the slab. Moisture will wick up.

Fix: Laminated floating floor guaranteed against water like Formica brand laid over the foam cushion which is over 5 mil plastic sheeting, with sealed seams extending up the walls under the baseboard.

Answer 9

sounds like you are in a wet area and a moisture barrier wan't installed under concrete,moisture will wick up thru the concrete.hopfully the can dry it out..good luck

Answer 10

I think you have a grasp of the problem,

Nope, I can't help...

Unless you are in a position to start over. I did get to help break up 100 cubic yards of concrete, once, and I assure you it is more fun to watch!