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QUESTION: Dear Mr Bruce Johnson for AllExperts:

The new construction was completed in Mar 2009 with concrete garage floor and polyaspartic coating was applied in Nov 2009.  In Sep 2012, we started seeing a spot on the garage floor by the rolling door oozing dark colored liquid.  We found no dripping from above and had wiped the area a few times, but the oozing continues.  Any idea what the problem might be?  The foundation or the coating?

Sincerely,
JL
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ANSWER: Hi J, first we need to eliminate some potential culprits.  Is there a piece of machinery or vehicle that sits in that spot that could be dripping oil or other fluids? I know you probably already considered that but I wanted to rule it out.  Secondly what kind of drainage do you have around the building?  And is this garage in an area with a high water table?  Could there be an old septic tank, fuel storage tank or old sewer pipe under the slab?  Whatever is making the spot appears to be oil based, have you had it analyzed?   I can't see how this could be related to the floor coating with the exception that it appears to have a hole in it through which the ooze is coming through.  

Regarding the construction of the slab. Was a vapor barrier installed under the concrete? Most cases of material seeping up through a concrete slab is related to improper drainage around the building which allows the ground water to build up and hydrostatic pressure pushing against the bottom of the slab forces water to find the path of least resistance.  Sometimes it's a crack, sometimes it's a pinhole such as what you have.  If you were to drill through the slab in that area you might find that a small fountain will erupt from all the upward pressure from below.  

Because it takes pressure to create a situation like this, that is why you need to rule out broken water or sewage lines, old buried tanks etc.  If you have a perimeter drain around the building you might want to make sure it is still operational.   Especially if the surrounding elevations are higher than the garage floor.  Water will seek its own level.  This may also be why the spot is closer to the outside door. Is there a roof drain leader nearby?  Or some other form of water supply?  A sprinkler head?

I'm just throwing out some ideas..if you'd care to get back to me with some more info, I might be able to narrow it down further.  But I think we can rule out the coating for now...sincerely Bruce Johnson

---------- FOLLOW-UP ----------

QUESTION: Dear Mr Bruce Johnson for AllExperts:

Thank you for replying back so quickly, and sorry for not writing back sooner.  Please see below for our answers (A:) to your questions/comments.  We appreciate the good points you have made.

Is there a piece of machinery or vehicle that sits in that spot that could be dripping oil or other fluids?
A: Nothing has been above/over that spot.

I know you probably already considered that but I wanted to rule it out.  Secondly what kind of drainage do you have around the building?  And is this garage in an area with a high water table?
A: Probably not; the home is built on a terrace above street level sloping/grading away from the garage/home.

Could there be an old septic tank, fuel storage tank or old sewer pipe under the slab?  
A: No idea without asking the builder.  The site is a part of a regional park; and current home is the first above ground structure on the site.

Whatever is making the spot appears to be oil based, have you had it analyzed?
A: Not yet analyzed. The liquid is yellow and smells metallic, seems water based by touch and dries to dark brown.  

I can't see how this could be related to the floor coating with the exception that it appears to have a hole in it through which the ooze is coming through.

Regarding the construction of the slab. Was a vapor barrier installed under the concrete?
A: No idea without asking the builder.  The builder was going to inquire with his concrete contractor.

Most cases of material seeping up through a concrete slab is related to improper drainage around the building which allows the ground water to build up and hydrostatic pressure pushing against the bottom of the slab forces water to find the path of least resistance.  Sometimes it's a crack, sometimes it's a pinhole such as what you have.  If you were to drill through the slab in that area you might find that a small fountain will erupt from all the upward pressure from below.  

Because it takes pressure to create a situation like this, that is why you need to rule out broken water or sewage lines, old buried tanks etc.  If you have a perimeter drain around the building you might want to make sure it is still operational.   Especially if the surrounding elevations are higher than the garage floor.  Water will seek its own level.  This may also be why the spot is closer to the outside door. Is there a roof drain leader nearby?
A: A Gutter down spout is on the other end of the 3-car garage.

Or some other form of water supply? A sprinkler head?

Answer
Hi again J, hmm..you have a unique situation..it is possible that your home is built in an area where black mud exists.  Black mud is a form of soil that is a mixture of organic compounds and clay.  It can ooze when wet, and when pressure from a foundation or other load is applied to wet black mud it can be displaced and will try to seek its own level much like water.  Also, because of the clay content it will expand when wet, again as this happens it can create pressure.  Just as a glass of water will overflow when filled with marbles so too can black mud react when displaced by a heavy object, in this case your garage foundation.  I've seen this phenomenon in the Pacific Northwest and many of the homes I built in those black mud areas had specialized foundations with poured concrete pilings whose holes were bored beyond the layer of black mud down to a more solid stratum of rock.  Look for signs of settlement around your foundation.  As I mentioned above, if the oozing is the soil underneath your foundation being displaced and forced up through a pinhole in your slab then there should be some other evidence somewhere around this same location.  Bulging earth at  your foundation perimeter and/or signs of settling.  Sincerely Bruce Johnson  

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Bruce E. Johnson

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I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.

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Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.

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