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Basement Slab Encapsulate

I have a 1940s era home.  In the center of my slab I noticed water come up through vinyl tile periodically when we had consistent and significant soaking rains (via hydrostatic pressure).  I removed the vinyl tile and uncovered black mastic along with a horrendous smell.  It was wet under some of the tiles while others were dry and secure.  Keep in mind these tiles were installed by a prior owner.  The original asbestos tiles were removed a long time ago.  I removed the black mastic using a product from Franmar called Bean-a-doo.  I noticed a hairline crack in the center of the slab about 10 feet long consistent with where the water was coming up through the vinyl tile.  From there I degreased the floor several times, cleaned it several times.  I also rented a HEPA air purifier from HD with a charcoal filter and ran it for a week 24/7.  The smell is still there over a month later.  I can't run my HVAC as I don't want it circulating around the house, but that time is running out soon.  Here's my plan....get the floor ground so there's a clean surface and repair the crack..  I'm looking at what to use to seal and encapsulate the floor so it provides waterproofing and most importantly, gets rid of the smell.  Any thoughts on my plan and what should I use to encapsulate?  I heard that the Behr paint wouldn't be strong enough to encapsulate.  I also heard of this product called Aquafin SG3 but that's over $500 for 1.5 gallons.
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Posted 2017-09-15T14:32:35+0000  by BrianDIY BrianDIY


Go to You Tube and type in RedGard. This product is used as a moisture barrier under tile work and under carpets and wood floors that are on cement floor below grade. It is rolled on in a continuous "paint' film and is capable of sealing in a crack of up to 1/8th inch. Fiberglas mesh can also be embedded in it to span crack areas. Home Depot does carry this product in the flooring and tile department.

A home of this age would not commonly have had a vapor barrier underneath before the concrete was poured. Neither would it have had a drain tile and sump pump arrangement. The RedGard should form a continuous water/vapor barrier on the living space side of the concrete.
Posted 2017-09-16T02:11:42+0000  by ordjen

Hello BrianDYI and welcome to the Community.


I think you need to take a three-step approach. 

To help remove the smell open up all the windows in the house and run the fan on your furnace/ air conditioner to expel the odor to the outside.


Next, you must fix the crack.  Here is a link to an example of how to repair the crack.

Here is a link to some of the product chooses at Home Depot, for repairing the crack.  I believe the epoxy filler are the best for this application.


Lastly, move the water away from your house.

Foundation grading establishes a land slope away from the house that uses gravity to direct rainwater and snowmelt away from the foundation.  On average, the slope is 6” for every 10 feet but check your local codes

To prevent water from leaking through your foundation, look to gutters and downspouts as your first line of defense.  Carry water as far away from the foundation as possible by attach downspout extensions.  You can even use a 10’ vertical down spout or 4” drain pipe with connector as an extension.

If you have, a sump pump increasing distance of the expelled water will decrease the saturation of the ground by the foundation thus reducing the cycles of the sump pump and extending its life. These hoses can be coiled and hidden during dry spells.

Install a French drain around the perimeter, to collect and remove the water.


If your problem persist after you have fixed the crack, you may need a professional waterproofing company.

Thank your inquiry.


Posted 2017-09-19T19:23:31+0000  by Char_HD_CHI

I doubt that fixing the crack only will address the entire problem. Concrete itself is very porous and is passing moisture through which gets generally trapped behind the tile and causes odor.My guess, although you don't state so, is that there is a constant musty odor down there. Short of tearing up the perimeter of the floor and installing a drain and sump pump system, Obviously, if the ground water level is significantly below the slab, the slab will not leak. This is what sump pump systems do - they artificially lower the ground water level under our slab.

I doubt that fixing the visible crack will solve your problem. The RedGard would definitely help is stopping the water vapor that is permeating the slab. It should also stop water coming through a "hairline" crack.
Posted 2017-09-20T17:45:06+0000  by ordjen
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