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Old 05-22-2019, 12:01 PM   #1
kg0rp
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Moisture from slab sub-floor permeating grout

Hello to the forum, I have a problem with water coming up through the grout between tiles in a portion of my rental property. It comes up through the grout and puddles. If the puddles are allowed to remain for a couple of days they deposit a white residue that has to be removed with a razor blade.

A very large portion of this 2000 sq ft house is tiled, all with the same tile, so tearing out the tiling as a repair isn't practical. Especially since the water is only coming up in the living area. It is coming up in about ten different spots.

I have a few spare tiles and I thought I'd sacrifice one and proceeded to break out a tile where the puddling seemed the worse. I was pretty horrified at what I found. It seems like there is an incredibly thick layer of mortar over the concrete slab, and this mortar appears to be very wet and is disintegrating. Reference the attached pictures.

The property is in Tampa in an area that has a very high water table. The house was built in the 80's but the tile floor was probably installed (very inexpertly I might add) by a previous owner and is probably less than six years old. I have since found out that many neighbors have the same issue. It appears to be due to the membrane they used under the concrete slab has probably deteriorated and is allowing ground moisture to permeate the slab into the house.

As I said at the beginning of this post, replacing the entire floor because of 10 wet spots wouldn't be my first choice of solutions!

So, if you've made it to the bottom of this long post; here is my question:

Would removing the cementitious grout and replacing it with epoxy grout stop the water from coming up and pooling on the floor? While I wouldn't look forward to removing all that grout, it would have to be a lot less expensive than a tear out and re-do.

Any thoughts would be greatly appreciated!

Tom
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Old 05-22-2019, 08:39 PM   #2
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Welcome to the forum, Tom.

With hydrostatic pressure like that, something's gotta give. I imagine you'd just force the moisture to the nearest place it could come up.

Maybe it wouldn't, can't say for sure. I wouldn't do what you're proposing if I wasn't pretty sure it would fix the problem. That could be a lot of time, work, and money for nothing.
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Old 05-23-2019, 07:34 AM   #3
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Without knowing how much hydrostatic pressure there is, it is a total gamble.

Hydrostatic pressure can be enough to move your entire home. The solution is NEVER to just cover it with tile and grout. Even membranes design to mitigate it have a limitation.

Maybe it will work, but who knows. In my opinion, the only real solution is to have no flooring at all. If the moisture can evenly come out of the entire slab, it would probably not pool up and just permeate as vapor. A whole home dehumidified would be the solution.

Good luck!

https://www.concretetreatmentsinc.co...atic-pressure/

Many concrete floors with hydrostatic pressure issues are not good candidates for secondary floor coverings. Carpet will remain damp and become musty or the glue that holds vinyl and other flooring options will let loose. What is the solution for such a problem?

Polished Concrete is the solution. When a floor is mechanically polished, there are no additional topical sealers or coverings that are inhibiting the moisture to come out of the slab thus allowing the floor to continue to breathe. Even though a densifier/hardener is applied to the slab, this sealer soaks into the concrete and the reaction takes place at a molecular level so this process doesn’t have any effect on the concrete slabs’ ability to mitigate moisture. In most cases, polished concrete is the only solution for a high rate of moisture through the slab, but it isn’t a bad thing. Take a look at the picture below that had hydrostatic pressure going on in the slab that we polished. They still look great and you’d never know that there was a major problem with this floor at one time.
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Old 05-23-2019, 08:15 AM   #4
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Does this property have a sump pump? Is that even an option in your area?

Seems like it might be the best place to start to lower the water table in the area immediately around the property.
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Old 05-23-2019, 09:51 AM   #5
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if the water table is indeed always that high I do not think a sump pump (at least not a single one) will do much. A sump is more for issues like drain water during a storm.
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Old 05-23-2019, 09:52 AM   #6
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With the exception of the addition of one or many sump pumps and exterior water mitigation (gutters, proper slope around the home, etc...), I don't see much of an option other than a full tear out. Epoxy grout has a low perm rating and you may deal with other issues down the road as water attempts to follow the path of least resistance.

As mentioned before, removing the mortar/tile and polishing the concrete if it's in good shape might be your best bet.
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Old 05-23-2019, 10:11 AM   #7
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I respectfully disagree speed.

Sump pumps/dewatering is pretty common method of dealing with a high water table, especially in basements when used with appropriate waterproofing. Yeah they might run a lot, but if the intent is to keep the original flooring intact.

In this case Tom is getting hydrostatic pressure coming up through his floor through a punctured (or possibly nonexistant) vapor barrier. That failed vapor barrier is now working against him by not allowing water to easily drain from underneath the slab. Blowing the entire tile assembly to allow his floor to breath via polish concrete (and also dump a ton of moisture into the air of what is probably a home in a continually moist environment) is the last think I would ever want to do. Especially if it is rental property that might sit vacant and un or minimially conditioned for long periods is inviting mold growth.

In this case I'm assuming that this place doesn't have a basement the sump pit will do lot of work initially to dewater the surrounding area relative to its pit depth. But after that the pump will just need to work a bit to maintain the dip in the water table under the house. Which will primarily depend on the soil type.
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Old 05-23-2019, 01:25 PM   #8
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Given the geography of the Tampa area (almost all sand), the stated very high water table, that Floridian construction almost never has a basement, and the fact neighbors have a similar issue, I respectfully disagree as well.

Just because you have a sump pump doesn't mean you can build your home on water. Any water you pump will have to go somewhere. You can rule out the sewer as it is illegal everywhere I know of. The sand will allow it to infiltrate back very fast.

You are going to have to pump constantly. Think a canoe with a hole in it. You can bail the water all you want, but it will just keep coming and coming. Plus you have to pump faster than it returns.

Tom, what was there before you tiled? Was there ever any water spots before? Is this a new place you purchased and are unaware of its history?

Also, did you do any drilling or breaking up of concrete? Do you have plumbing in the slab? Have you considered a ruptured water line?
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Old 05-23-2019, 01:47 PM   #9
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The point I was trying to make with a sump is that at grade it's going to have to do a heck of a lot less work to drop the water table to a manageable level.

By placing a sump pump you create a cone of depression in the water table around the house. In this case the cone doesn't need to be very deep to have a clear and immediate effect on what Tom is experiencing.

It is by far the cheapest and most effective first step.

Not knowing how storm water is managed they might have separate storm drains, in which case they water might be able to be pumped directly to or in the vicinity of that drain.

In certain geophraphic areas a sump that runs consistently all the time is not an uncommon thing.
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Old 05-23-2019, 02:39 PM   #10
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Mike,

In SE michigan wetlands where I owned a home previously, the water table was managed by our subdivision's series of sump pumps and storm drains. The pump would run for hours a day. proper grading and rainwater mitigation from the immediate area surrounding the home reduced some of the load on our sump pump as it ran less often.

In my current home, the sump pump feeds directly into the storm drain with no issue from local building inspectors.

As for polished concrete, I think the combination of polished concrete and a drain/sump system would benefit the OP. Humidity in a southern Florida home is managed by the AC unit that runs 70% of the year so that shouldn't be an issue either. I've seen a lot of Florida homes without rain gutters and yards that slope towards a slab on grade, fixing those issues will also help.

OP, your best bet is to consult with a foundation specialist and focus on your water intrusion as none of us truly know what is causing your issue without further investigation. Once that is managed, then I'd worry about your tile/thinset situation.
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Old 05-23-2019, 07:27 PM   #11
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Since it's coming up in ten places around the room, I'd say it's not likely to be a punctured water line.

I had the same issue in my house when I had to break out some of the slab and cut the vapor barrier underneath.

Although I put plastic back in the trench before replacing the concrete, it wasn't tied in to the original barrier. So moisture would come up at those places directly above the open seams. It evaporated and was never visible when uncovered, but I laid Ditra over it, and before bonding it to the floor, I could lift it and see moisture collecting.
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Old 05-25-2019, 09:17 AM   #12
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Thanks for the advice and comments

A big thanks to members of the forum that have offered advice and thoughts about my moisture problem! I really appreciate the input, even bad news is good news, ignorance of what's going on is the worst.

To give a little more background, I bought the house three years ago with the intent of using it as a Winter/vacation home. When that didn't work out I decided to turn it into a rental.

When I checked the house out prior to purchase, there was furniture and LARGE area rugs in the living room. I noticed that the tile was inexpertly installed, but was willing to look past that. Now I know why there were large area rugs! It became apparent about a week into owning the place. That's when I broke up a tile to have a look at what was going on underneath and took the pictures I posted with this thread.

Yes, I did have the plumbing pressure tested and that didn't uncover anything. There is no possibility of installing a sump pump, let alone multiple pumps as there is no basement. I think some gutter work could possibly help, and I'm going to try it, but I'm not super hopeful.

The rate of water infiltration doesn't seem to be affected by rainy seasons or downpours. It is present event during the dry season. This is according to my tenant that has lived there for the past 3 years. This alone makes me suspect either groundwater or a plumbing issue that was not detected by the pressure test, something I might have done a second time just to make sure there are no leaks.

So what am I going to do about it? Nothing, at least for now. Comments from the forum about the epoxy grout have made me nervous about redirecting water under the tile field to the perimeter; causing damage to the walls. I'm not in a financial position to rip out a thousand square feet of tile to uncover a slab surface of unknown quality.

Bottom line; the tenants will have to mop up the little puddles..

Thanks to all!

Tom
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Old 05-25-2019, 09:28 AM   #13
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This is a common Florida problem. There is either no vapor barrier or a compromised vapor barrier. Have been doing those types of claims for years. Epoxy grout will make it worse by causing the floor to loosen at a more rapid rate. Had one job where they did that and the white powdery coating turned into white volcanos. You will need a vapor diffusion or reduction system when it goes back in. Take the price of a normal tile job and double it from a budget perspective.
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Old 05-25-2019, 10:42 AM   #14
kg0rp
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I'm convinced now

Thanks Dave. Your comments push me over the edge about the epoxy grout! I was already concerned about forcing the water to the perimeter of the field anyway. Guess I'll just live with the problem (to be more accurate, my tenants will) until I sell the house next year.
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Old 05-25-2019, 12:25 PM   #15
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The majority of the time people push it to the edge with no problem. However, they do make a ventilation strip that channels it out into the room rather than up the wall. The oldest one I was involved with and still converse occasionally pushed it to the wall with no problems the last 15 or so years.
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