water concrete floor??

[mnpeterg]

new shed build (30x16). monolithic slab 12 inch footer, 6 inch floor. concrete was poured about 8 or 9 weeks ago. Walls and roof have been up for a few weeks. Today I noticed a wet spot on the on the concrete floor (see attached pictures). (about 18 inches from the edge of the footer. We have had a decent amount of rain over the past several days. It is not from the roof, I’m thinking it’s from the under..??

-I did put a very thick (15mil) vapor barrier under the pour.-


Thoughts?


I do plan to use some self leveling concrete in a few weeks to level some areas. Possibly put a bit over that area.. any ideas...

 

[Shiftless]

Here are some pertinent questions. :

Is that slab well above the soil on all 4 sides with soil sloping away from the building? Does your building have gutters and downspouts with drain pipe carrying the rainwater well away from the building? I assume your heavy plastic was not seamless. Is the wet spot near a seam or overlap? Did you bring the plastic membrane up and over the sides of the slab?

Can you be absolutely completely positive that the roof doesn’t have a small leak?

BTW, many here on GJ will be of the opinion that the level of finish of that pour is less than first class.

 

[mnpeterg]

The slab is a few inches above the soil, the concrete blocks that sit on the footer have also been drylocked.

No gutters.

The moisture barrier did have a seam, and I use the ‘special tape’ from the manufacture for under slab moisture barrier.


Could the water under the slab really be penetrating after 2 months a 6 inch slab with a decent barrier?



I’m as certain as I can be that its not from above.

Would putting a thin coat of concrete over it help?

 

[ConCretin]

it's very unlikely that water is coming through the floor and pooling in one specific area with or without a vapor barrier. Moisture traveling through a concrete floor is almost always in the form of vapor. I'd be looking for a source from above the slab related to the recent rain.

 

[Shiftless]

Would putting a thin coat of concrete over it help?

I’m no expert. I did a thin overlay on a crappy looking 8x8 slab that used to have a hot tub sitting on it for 20 years. The slab was not finished too carefully because it was poured for the sole purpose of supporting a huge tub of hot water.
After the kids left home, the spa started leaking and we didn’t use it much. I cut it up and hauled it to the dump.
Anyway, the slab looked bad with irregular finish and stains. I DIY’ed a thin overlay and a broom finish. It held up well. It’s about 5 years old.
But it gets only occasional foot traffic and no vehicles at all not even a lawn mower.

I would fear that for a working garage, any thin overlay might crack and separate and or flake off leaving you a big mess.

 

[Uncle murph]

new shed build (30x16). monolithic slab 12 inch footer, 6 inch floor. concrete was poured about 8 or 9 weeks ago. Walls and roof have been up for a few weeks. Today I noticed a wet spot on the on the concrete floor (see attached pictures). (about 18 inches from the edge of the footer. We have had a decent amount of rain over the past several days. It is not from the roof, I’m thinking it’s from the under..??

-I did put a very thick (15mil) vapor barrier under the pour.-


Thoughts?


I do plan to use some self leveling concrete in a few weeks to level some areas. Possibly put a bit over that area.. any ideas...

Looks more like oil to me,that being said,anything that’s at a temperature below the dew point particularly in humid weather is going to get wet and vapor barrier won’t change a thing.

 

[BillK]

Where are you located ? Big temperature changes lately ? Might just be condensation on a cool spot on the floor.

 

[Beauregard]

Is there any chance the neighbor's cat or dog didn't get in there and squat?

 

[OccupantRJ]

You have any practical joker friends?

 

[Uncle murph]

Is there any chance the neighbor's cat or dog didn't get in there and squat?

I’m actually starting to think something fishy.

 

[Fixr]

I’m actually starting to think something fishy.

The water isn't deep enough for a fish.

 

[lolaetype]

Is there any chance the neighbor's cat or dog didn't get in there and squat?

That's the same thing I was thinking.

 

[dcg9381]

Looks more like oil to me,

Time for a "taste test".

Which will make it even better if it's the neighbors cat or a practical joke.

 

[Shiftless]

If it was water (or ???) coming from the top side, I would guess that it would have dried up by now.