# Basement Slab moisture



## overanalyze (Dec 28, 2010)

Built my house in 2004. Not 100% sure if there is a vapor barrier under the slab. I don't remember if the foundation guy used one before they poured the slab or not. The basement slab is sealed. I have never had water in the basement. I have a 2 sump pit setup where the inside footer tile and outside footer tile are 100% separate. 

My issue... I recently put down glue down vinyl flooring. Moisture is coming up through the joints in the floor in one area. 

I am thinking it must be moisture wicking through the slab, collecting under the vinyl plank floor and now is showing up as it builds. Before when there wasn't any flooring the moisture must have still been present but was able to evaporate. This isn't all over but in on area. 

I have good fall away from the house and downspouts go into tile tied into the city storm sewer. 

My thought on solving it...install a radon fan. We don't have radon in my area...or at least no one has those systems that I have ever ran across. The one thing I read that is a side effect of installing a radon system was drastically lowered basement moisture readings. So since my two sumps are separate I can put a sealed lid on my inside sump pit, draw air out of that pit and exhaust it outside. 

Thoughts?


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## Morning Wood (Jan 12, 2008)

Maybe. Won't know until you try it. Of course, you know what it will take to fix for sure.


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## overanalyze (Dec 28, 2010)

Morning Wood said:


> Maybe. Won't know until you try it. Of course, you know what it will take to fix for sure.


I presume you mean to verify if a vapor barrier does exist?

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## griz (Nov 26, 2009)

I do not see how that will stop moisture coming through the slab.

What is the slab sealed with?


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## overanalyze (Dec 28, 2010)

I will have to look up the brand. It was a penetrating sealer. It was supposed to bond chemically with the concrete. 

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## griz (Nov 26, 2009)

Did you moisture test prior to floor install?


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## overanalyze (Dec 28, 2010)

griz said:


> Did you moisture test prior to floor install?


I did a 24 hour visqueen test. Tape the visqeen down and see what accumulates. Nothing. The floor has been down for a couple months and is just showing this in the last couple weeks. 

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## Morning Wood (Jan 12, 2008)

overanalyze said:


> I presume you mean to verify if a vapor barrier does exist?
> 
> Sent from my SM-T310 using Tapatalk




Maybe the radon fan will fix your problem. Won't know until you try it. 

Right. Cut a hole and see if there is vapor barrier. Of course, just because there is doesn't mean it was installed correctly.


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## overanalyze (Dec 28, 2010)

I know there is plenty of crushed stone under the slab. I remember seeing the basement after the walls were stripped. I just can't say whether or not they placed a vapor barrier before they poired the slab...hell I can't remember last week some days. 

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## griz (Nov 26, 2009)

overanalyze said:


> I did a 24 hour visqueen test. Tape the visqeen down and see what accumulates. Nothing. The floor has been down for a couple months and is just showing this in the last couple weeks.
> 
> Sent from my SM-T310 using Tapatalk


visqueen was dry and no discoloration on slab?


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## overanalyze (Dec 28, 2010)

griz said:


> visqueen was dry and no discoloration on slab?


Yep...I will admit I didn't test in multiple spots and I didn't test this area. Hindsight....

I know the fan is treating a symptom and not the disease, but short of ripping out the slab and re-pouring on a proper vapor barrier, presuming that's the issue, (that isn't going to happen) what are some alternative choices? 

The fan should depressurize the stone/soil underneath and vent that humid air to the exterior. If the stone underneath dries out wouldn't that stop wicking from the stone through the slab? 

Part of my question is a desire to fix my personal basement issue, part of it is to learn if there potential options if I encounter this in the future.


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## griz (Nov 26, 2009)

In your OP you state "moisture coming up through the joints".

Describe the moisture. Why do you think it's moisture?

Could be excess adhesive.


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## overanalyze (Dec 28, 2010)

When I press on the vinyl plank at the seams, a small amount of water comes up between the two planks. The adhesive was a pressure sensitive adhesive applied with the appropriate trowel and allowed to skin as recommended.


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## Seven-Delta-FortyOne (Mar 5, 2011)

Option 2: Pull the vinyl flooring and acid-stain the concrete.



Delta


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## Fouthgeneration (Jan 7, 2014)

If the washed rock is at least 3-4 inches everywhere, most likely the damp spot is where the rock isn't very thick, allowing water to travel via capillary to under the vinyl pieces or as water vapour till it condenses out under the vinyl.

the Constant air flow of the "radon" fan will add to your air conditioning costs year around and bring in a noticeable amount of dust for extra house cleaning and HVAC maintenance

Your basement floor temps aren't below your dew point of the house air during wash days or shower times?

A new slab(2-3") over a working vapour barrier and a 1" of dense foam if you have vertical room.:thumbsup:


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## overanalyze (Dec 28, 2010)

Not sure I follow how running the fan and drawing air out from under the slab and exhausting to the exterior will raise my AC Bill and cause a dirty house??


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## slowsol (Aug 27, 2005)

They make topical applied moisture barriers for under flooring. Sometimes their is a specific flooring adhesive that will work for your flooring that doubles as a moisture barrier. We use these in situations when we cannot get the humidity of the slab low enough to install flooring. 


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## griz (Nov 26, 2009)

slowsol said:


> They make topical applied moisture barriers for under flooring. Sometimes their is a specific flooring adhesive that will work for your flooring that doubles as a moisture barrier. We use these in situations when we cannot get the humidity of the slab low enough to install flooring.
> 
> 
> Sent from my iPhone using Tapatalk


There is an adhesive that you can dam near use underwater.

Found out a few years back on the gym I built.


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## Morning Wood (Jan 12, 2008)

overanalyze said:


> Not sure I follow how running the fan and drawing air out from under the slab and exhausting to the exterior will raise my AC Bill and cause a dirty house??




Not sure I get that either. A radon fan is pretty low flow just negative pressure really. Only thing going against you is you don't have radon piping throughout slab to equalize where your pulling from. Might not even matter. 

Nothing beats a good drain to clear sky and foam and 10 mil poly under a slab though.


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## overanalyze (Dec 28, 2010)

Yeah the inside footer tile is a sch35 perf pvc. I am going to try it I think...can't hurt. Fans are pretty affordable. 

If that doesn't work then I will source a different glue.


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## Morning Wood (Jan 12, 2008)

overanalyze said:


> 4th Gen...do you disagree with my solution?




He just disagrees with everyone.


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## Fouthgeneration (Jan 7, 2014)

No, if You can achieve a vapour 'proof' bond to the concrete with the epoxy you're should be good and dry....

Please post back in a year or two the results.
On sticky AC days the near ground temp slab might, still collect condensation from the air if its dew point is above the floor temperature.....

Damp vinyl linoleum has to be much less as of a mold factory then carpet in the same conditions.


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## overanalyze (Dec 28, 2010)

I am using EliteCrete's waterborne, 2 part epoxy vapor barrier. I will be applying 2 coats. My flooring guy does epoxy floor coatings and had this equipment and let me rent it. 

This is an Edco Floor grinder and Edco 200cfm vac. 99% dust free set up. I am amazed at how quick it grinds the slab. I have on the "fine" shoes. The small round ones. The blue and orange are more aggressive. My flooring guy said the more aggressive ones will tear up a slab in a heartbeat! This will give the epoxy a fresh surface to penetrate and adhere to.


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## cedarboarder (Mar 30, 2015)

I wanna use it!


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## overanalyze (Dec 28, 2010)

cedarboarder said:


> I wanna use it!


Ha! It is pretty uneventful to run. Renting a Husqvarna unit tomorrow for a bunch of thinset removal. Be curious to see how they differ.


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## DiaperRiot (Sep 27, 2017)

Take up the planks, and install some moisture mitigating epoxy. That would block the moisture.


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## overanalyze (Dec 28, 2010)

DiaperRiot said:


> Take up the planks, and install some moisture mitigating epoxy. That would block the moisture.


Umm..have you read any of the topic?...it is what I am doing. 

Here is some update pics. I did the epoxy in 2 sections. 2 coats aren't required but recommended. I am not taking any chances so 2 coats it is. Here you can see it all ground, one section 2 coated, and the first coat on the 2nd section.


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